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In polymer chemistry, polymerization ( American English), or polymerisation ( British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many forms of polymerization and different systems exist to categorize them.

In chemical compounds, polymerization can occur via a variety of reaction mechanisms that vary in complexity due to the functional groups present in the reactants and their inherent steric effects. In more straightforward polymerizations, alkenes form polymers through relatively simple radical reactions; in contrast, reactions involving substitution at a carbonyl group require more complex synthesis due to the way in which reactants polymerize. Alkanes can also be polymerized, but only with the help of strong acids.

As alkenes can polymerize in somewhat straightforward radical reactions, they form useful compounds such as polyethylene and polyvinyl chloride (PVC), which are produced in high tonnages each year due to their usefulness in manufacturing processes of commercial products, such as piping, insulation and packaging. In general, polymers such as PVC are referred to as " homopolymers," as they consist of repeated long chains or structures of the same monomer unit, whereas polymers that consist of more than one monomer unit are referred to as copolymers (or co-polymers).

Other monomer units, such as formaldehyde hydrates or simple aldehydes, are able to polymerize themselves at quite low temperatures (ca. −80 °C) to form trimers; molecules consisting of 3 monomer units, which can cyclize to form ring cyclic structures, or undergo further reactions to form tetramers, or 4 monomer-unit compounds. Such small polymers are referred to as oligomers. Generally, because formaldehyde is an exceptionally reactive electrophile it allows nucleophilic addition of hemiacetal intermediates, which are in general short-lived and relatively unstable "mid-stage" compounds that react with other molecules present to form more stable polymeric compounds.

Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous. This phenomenon is known as hazardous polymerization and can cause fires and explosions.

Step-growth and chain-growth are the main classes of polymerization reaction mechanisms. The former is often easier to implement but requires precise control of stoichiometry. The latter more reliably affords high molecular-weight polymers, but only applies to certain monomers.

Step-growth

In step-growth (or step) polymerization, pairs of reactants, of any lengths, combine at each step to form a longer polymer molecule. The average molar mass increases slowly. Long chains form only late in the reaction.

Step-growth polymers are formed by independent reaction steps between functional groups of monomer units, usually containing heteroatoms such as nitrogen or oxygen. Most step-growth polymers are also classified as condensation polymers, since a small molecule such as water is lost when the polymer chain is lengthened. For example, polyester chains grow by reaction of alcohol and carboxylic acid groups to form ester links with loss of water. However, there are exceptions; for example polyurethanes are step-growth polymers formed from isocyanate and alcohol bifunctional monomers) without loss of water or other volatile molecules, and are classified as addition polymers rather than condensation polymers.

Step-growth polymers increase in molecular weight at a very slow rate at lower conversions and reach moderately high molecular weights only at very high conversion (i.e., >95%). Solid state polymerization to afford polyamides (e.g., nylons) is an example of step-growth polymerization.

Chain-growth

In chain-growth (or chain) polymerization, the only chain-extension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical, cation, or anion. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers. Long chains are formed from the beginning of the reaction.

Chain-growth polymerization (or addition polymerization) involves the linking together of unsaturated monomers, especially containing carbon-carbon double bonds. The pi-bond is lost by formation of a new sigma bond. Chain-growth polymerization is involved in the manufacture of polymers such as polyethylene, polypropylene, polyvinyl chloride (PVC), acrylate. In these cases, the alkenes RCH=CH ₂ are converted to high molecular weight alkanes (-RCHCH ₂-) n (R = H, CH ₃, Cl, CO ₂CH ₃).

Other forms of chain growth polymerization include cationic addition polymerization and anionic addition polymerization. A special case of chain-growth polymerization leads to living polymerization. Ziegler-Natta polymerization allows considerable control of polymer branching.

Diverse methods are employed to manipulate the initiation, propagation, and termination rates during chain polymerization. A related issue is temperature control, also called heat management, during these reactions, which are often highly exothermic. For example, for the polymerization of ethylene, 93.6 kJ of energy are released per mole of monomer.

The manner in which polymerization is conducted is a highly evolved technology. Methods include emulsion polymerization, solution polymerization, suspension polymerization, and precipitation polymerization. Although the polymer dispersity and molecular weight may be improved, these methods may introduce additional processing requirements to isolate the product from a solvent.

Photopolymerization

Most photopolymerization reactions are chain-growth polymerizations which are initiated by the absorption of visible or ultraviolet light. The light may be absorbed either directly by the reactant monomer ( direct photopolymerization), or else by a photosensitizer which absorbs the light and then transfers energy to the monomer. In general only the initiation step differs from that of the ordinary thermal polymerization of the same monomer; subsequent propagation, termination and chain transfer steps are unchanged. In step-growth photopolymerization, absorption of light triggers an addition (or condensation) reaction between two comonomers that do not react without light. A propagation cycle is not initiated because each growth step requires the assistance of light.

Photopolymerization can be used as a photographic or printing process, because polymerization only occurs in regions which have been exposed to light. Unreacted monomer can be removed from unexposed regions, leaving a relief polymeric image. Several forms of 3D printing-including layer-by-layer stereolithography and two-photon absorption 3D photopolymerization -use photopolymerization.

Multiphoton polymerization using single pulses have also been demonstrated for fabrication of complex structures using a digital micromirror device.

In a given formulation or recipe of a polymer compound, the total amount/parts per hundred of polymer added to prepare certain compound is called polymer ratio. It basically refers to the aggregated amount of polymer content within the formulation that may undergo any physical or chemical change during the course of post polymerization or physical heat treatment.

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In polymer chemistry, polymerization ( American English), or polymerisation ( British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many forms of polymerization and different systems exist to categorize them.

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Polymerisation of Ethene | Organic Chemistry | Chemistry | FuseSchool

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World Energy Council. (October 3, 2016). Boiling temperature of selected petroleum products (in degrees Celsius) [Graph]. In Statista. Retrieved January 14, 2021, from https://www.statista.com/statistics/698387/selected-petroleum-products-boiling-temperature/

World Energy Council. "Boiling temperature of selected petroleum products (in degrees Celsius)." Chart. October 3, 2016. Statista. Accessed January 14, 2021. https://www.statista.com/statistics/698387/selected-petroleum-products-boiling-temperature/

World Energy Council. (2016). Boiling temperature of selected petroleum products (in degrees Celsius). Statista. Statista Inc.. Accessed: January 14, 2021. https://www.statista.com/statistics/698387/selected-petroleum-products-boiling-temperature/

World Energy Council. "Boiling Temperature of Selected Petroleum Products (in Degrees Celsius)." Statista, Statista Inc., 3 Oct 2016, https://www.statista.com/statistics/698387/selected-petroleum-products-boiling-temperature/

World Energy Council, Boiling temperature of selected petroleum products (in degrees Celsius) Statista, https://www.statista.com/statistics/698387/selected-petroleum-products-boiling-temperature/ (last visited January 14, 2021)

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Learn more about how Statista can support your business. World Energy Council. (October 3, 2016). Boiling temperature of selected petroleum products (in degrees Celsius) [Graph]. In Statista. Retrieved January 14, 2021, from https://www.statista.com/statistics/698387/selected-petroleum-products-boiling-temperature/ World Energy Council. "Boiling temperature of selected petroleum products (in degrees Celsius)." Chart. October 3, 2016. Statista.

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From Wikipedia, the free encyclopedia

The smoke point, also referred to as the burning point, is the temperature at which an oil or fat begins to produce a continuous bluish smoke that becomes clearly visible, dependent upon specific and defined conditions.[1] Smoke point values can vary greatly, depending on factors such as the volume of oil utilized, the size of the container, the presence of air currents, the type and source of light as well as the quality of the oil and its acidity content, otherwise known as free fatty acid (FFA) content.[2] The more FFA an oil contains, the quicker it will break down and start smoking.[2][3] The lower the value of FFA, the higher the smoke point.[dubious ][4] However, the FFA content typically represents less than 1% of the total oil and consequently renders smoke point a poor indicator of the capacity of a fat or oil to withstand heat.[4][5][6]

The smoke point of an oil correlates with its level of refinement.[7][8] Many cooking oils have smoke points above standard home cooking temperatures:[9]

Pan frying (sauté) on stove top heat: 120 °C (248 °F)

Deep frying: 160-180 °C (320-356 °F)

Oven baking: Average of 180 °C (356 °F)

Smoke point decreases at different pace in different oils.[10]

Considerably above the temperature of the smoke point is the flash point, the point at which the vapours from the oil can ignite in air, given an ignition source.

The following table presents smoke points of various fats and oils.

^ Specified smoke, fire, and flash points of any fat and oil can be misleading: they depend almost entirely upon the free fatty acid content, which increases during storage or use. The smoke point of fats and oils decreases when they are at least partially split into free fatty acids and glycerol; the glycerol portion decomposes to form acrolein, which is the major source of the smoke evolved from heated fats and oils. A partially hydrolyzed oil therefore smokes at a lower temperature than non-hydrolyzed oil. (Adapted from Gunstone, Frank, ed. Vegetable oils in food technology: composition, properties and uses. John Wiley & Sons, 2011.)

Hydrolysis and oxidation are the two primary degradation processes that occur in an oil during cooking.[10] Oxidative stability is how resistant an oil is to reacting with oxygen, breaking down and potentially producing harmful compounds while exposed to continuous heat. Oxidative stability is the best predictor of how an oil behaves during cooking.[33][34][35]

The Rancimat method is one of the most common methods for testing oxidative stability in oils.[35] This determination entails speeding up the oxidation process in the oil (under heat and forced air), which enables its stability to be evaluated by monitoring volatile substances associated with rancidity. It is measured as "induction time" and recorded as total hours before the oil breaks down. Canola oil requires 7.5 hours, for example, whereas extra virgin olive oil (EVOO) and virgin coconut oil will last over a day at 110 °C of continuous heat.[9] The differing stabilities correlate with lower levels of polyunsaturated fatty acids, which are more prone to oxidation. EVOO is high in monounsaturated fatty acids and antioxidants, conferring stability. Some plant cultivars have been bred to produce "high-oleic" oils with more monounsaturated oleic acid and less polyunsaturated linoleic acid for enhanced stability.[9]

The oxidative stability does not directly correspond to the smoke point and thus the latter cannot be used as a reference for safe and healthy cooking.[36]

1. Thomas, Alfred (2002). Fats and Fatty Oils. Ullmann's Encyclopedia of Industrial Chemistry. Wenheim: Wiley-VCH. ISBN 978-3-527-30673-2.

2. ^ Bastida, SS; et al. (2001). "Thermal oxidation of olive oil, sunflower oil and a mix of both oils during forty continuous domestic fryings of different foods". Food Science and Technology International. 7: 15-21. doi:10.1106/1898-plw3-6y6h-8k22. S2CID 97919860.

3. Gennaro, L.; et al. (1998). "Effect of biophenols on olive oil stability evaluated by thermogravimetric analysis". Journal of Agricultural and Food Chemistry. 46 (11): 4465-4469. doi:10.1021/jf980562q.

4. ^ Gomez-Alonso, S.; et al. (2003). "Changes in phenolic composition and antioxidant activity of virgin olive oil during frying". J Agric Food Chem. 51 (3): 667-72. doi:10.1021/jf025932w. PMID 12537439.

5. ^ Chen, W.; et al. (2013). "Total polar compounds and acid values of repeatedly used frying oils measured by standard and rapid methods" (PDF). J Food Drug Anal. 21 (1): 85.

6. ^ Boickish, Michael (1998). Fats and oils handbook. Champaign, IL: AOCS Press. pp. 95-96. ISBN 978-0-935315-82-0.

7. ^ Morgan, D.A. (1942). "Smoke, fire, and flash points of cottonseed, peanut, and other vegetable oils". Oil & Soap. 19 (11): 193-198. doi:10.1007/BF02545481. S2CID 93662177.

8. ^ Gray, S (June 2015). "Cooking with extra virgin olive oil" (PDF). ACNEM Journal. 34 (2): 8-12. Archived from the original (PDF) on 2020-11-12.

9. Monoj K. Gupta; Kathleen Warner; Pamela J. White (2004). Frying technology and Practices. AOCS Press, Champaign, Illinois.

10. ^ Jacqueline B. Marcus (2013). Culinary Nutrition: The Science and Practice of Healthy Cooking. Academic Press. p. 61. ISBN 978-012-391882-6. Table 2-3 Smoke Points of Common Fats and Oils.

11. ^ "Smoke Point of Oils". Baseline of Health. Jonbarron.org. 2012-04-17.

12. ^ Marie Wong; Cecilia Requejo-Jackman; Allan Woolf (April 2010). "What is unrefined, extra virgin cold-pressed avocado oil?". Aocs.org.

13. The Culinary Institute of America (2011). The Professional Chef (9th ed.). Hoboken, New Jersey: John Wiley & Sons. ISBN 978-0-470-42135-2. OCLC 707248142.

14. Detwiler, S. B.; Markley, K. S. (1940). "Smoke, flash, and fire points of soybean and other vegetable oils". Oil & Soap. 17 (2): 39-40. doi:10.1007/BF02543003.

15. "Introducing Nutiva Organic Refined Coconut Oil". Nutiva. Archived from the original on 2015-02-14.

16. ^ "Olive Oil Smoke Point".

17. ^ Gray, S (June 2015). "Cooking with extra virgin olive oil" (PDF). ACNEM Journal. 34 (2): 8-12.

18. (in Italian) ^ Scheda tecnica dell'olio di palma bifrazionato PO 64.

19. ^ Ranalli N, Andres SC, Califano AN (Jul 2017). "Dulce de leche‐like product enriched with emulsified pecan oil: Assessment of physicochemical characteristics, quality attributes, and shelf‐life". European Journal of Lipid Science and Technology. doi:10.1002/ejlt.201600377.

20. ^ "What is the "truth" about canola oil?". Spectrum Organics, Canola Oil Manufacturer. Archived from the original on April 13, 2014.

21. ^ "Organic unrefined sunflower oil".

22. ^ Fats and oils in human nutrition. Food and Agriculture Organization of the United Nations and the World Health Organization. 1994. ISBN 978-92-5-103621-1. Archived from the original on November 29, 2013.

23. ^ Nwosu, V.; et al. Oxidative Stability of various oils as determined by Rancimat Method. Department of Food Science.: North Carolina State University.

24. Methrom. "Oxidative stability of oils and fats - Rancimat method". Application Bulletin. 204/2 e.

25. ^ "Evaluation of Chemical and Physical Changes in Different Commercial Oils during Heating" (PDF).

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Toggle the table of contents From Wikipedia, the free encyclopedia The smoke point, also referred to as the burning point, is the temperature at which an oil or fat begins to produce a continuous bluish smoke that becomes clearly visible, dependent upon specific and defined conditions.[1] Smoke point values can

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Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation to fractionate. Generally the component parts have boiling points that differ by less than 25 °C (45 °F) from each other under a pressure of one atmosphere. If the difference in boiling points is greater than 25 °C, a simple distillation is typically used.

Fractional distillation in a laboratory makes use of common laboratory glassware and apparatuses, typically including a Bunsen burner, a round-bottomed flask and a condenser, as well as the single-purpose fractionating column.

A laboratory setup would include:

Discussion

As an example, consider the distillation of a mixture of water and ethanol. Ethanol boils at 78.4 °C (173.1 °F) while water boils at 100 °C (212 °F). So, by heating the mixture, the most volatile component (ethanol) will concentrate to a greater degree in the vapor leaving the liquid. Some mixtures form azeotropes, where the mixture boils at a lower temperature than either component. In this example, a mixture of 96% ethanol and 4% water boils at 78.2 °C (172.8 °F); the mixture is more volatile than pure ethanol. For this reason, ethanol cannot be completely purified by direct fractional distillation of ethanol-water mixtures.

The apparatus is assembled as in the diagram. (The diagram represents a batch apparatus as opposed to a continuous apparatus.) The mixture is put into the round bottomed flask along with a few anti-bumping granules (or a Teflon coated magnetic stirrer bar if using magnetic stirring), and the fractionating column is fitted into the top. The fractional distillation column is set up with the heat source at the bottom on the still pot. As the distance from the stillpot increases, a temperature gradient is formed in the column; it is coolest at the top and hottest at the bottom. As the mixed vapor ascends the temperature gradient, some of the vapor condenses and revaporizes along the temperature gradient. Each time the vapor condenses and vaporizes, the composition of the more volatile component in the vapor increases. This distills the vapor along the length of the column, and eventually the vapor is composed solely of the more volatile component (or an azeotrope). The vapor condenses on the glass platforms, known as trays, inside the column, and runs back down into the liquid below, refluxing distillate. The efficiency in terms of the amount of heating and time required to get fractionation can be improved by insulating the outside of the column in an insulator such as wool, aluminium foil or preferably a vacuum jacket. The hottest tray is at the bottom and the coolest is at the top. At steady state conditions, the vapor and liquid on each tray are at equilibrium. The most volatile component of the mixture exits as a gas at the top of the column. The vapor at the top of the column then passes into the condenser, which cools it down until it liquefies. The separation is more pure with the addition of more trays (to a practical limitation of heat, flow, etc.) Initially, the condensate will be close to the azeotropic composition, but when much of the ethanol has been drawn off, the condensate becomes gradually richer in water.[citation needed ] The process continues until all the ethanol boils out of the mixture. This point can be recognized by the sharp rise in temperature shown on the thermometer.

The above explanation reflects the theoretical way fractionation works. Normal laboratory fractionation columns will be simple glass tubes (often vacuum-jacketed, and sometimes internally silvered) filled with a packing, often small glass helices of 4 to 7 millimetres (0.16 to 0.28 in) diameter. Such a column can be calibrated by the distillation of a known mixture system to quantify the column in terms of number of theoretical trays. To improve fractionation the apparatus is set up to return condensate to the column by the use of some sort of reflux splitter (reflux wire, gago, Magnetic swinging bucket, etc.) - a typical careful fractionation would employ a reflux ratio of around 4:1 (4 parts returned condensate to 1 part condensate take off).

In laboratory distillation, several types of condensers are commonly found. The Liebig condenser is simply a straight tube within a water jacket, and is the simplest (and relatively least expensive) form of condenser. The Graham condenser is a spiral tube within a water jacket, and the Allihn condenser has a series of large and small constrictions on the inside tube, each increasing the surface area upon which the vapor constituents may condense.

Alternate set-ups may use a multi-outlet distillation receiver flask (referred to as a "cow" or "pig") to connect three or four receiving flasks to the condenser. By turning the cow or pig, the distillates can be channeled into any chosen receiver. Because the receiver does not have to be removed and replaced during the distillation process, this type of apparatus is useful when distilling under an inert atmosphere for air-sensitive chemicals or at reduced pressure. A Perkin triangle is an alternative apparatus often used in these situations because it allows isolation of the receiver from the rest of the system, but does require removing and reattaching a single receiver for each fraction.

Vacuum distillation systems operate at reduced pressure, thereby lowering the boiling points of the materials. Anti-bumping granules, however, become ineffective at reduced pressures.

Fractional distillation is the most common form of separation technology used in petroleum refineries, petrochemical and chemical plants, natural gas processing and cryogenic air separation plants. In most cases, the distillation is operated at a continuous steady state. New feed is always being added to the distillation column and products are always being removed. Unless the process is disturbed due to changes in feed, heat, ambient temperature, or condensing, the amount of feed being added and the amount of product being removed are normally equal. This is known as continuous, steady-state fractional distillation.

Industrial distillation is typically performed in large, vertical cylindrical columns known as "distillation or fractionation towers" or "distillation columns" with diameters ranging from about 0.65 to 6 meters (2 to 20 ft) and heights ranging from about 6 to 60 meters (20 to 197 ft) or more. The distillation towers have liquid outlets at intervals up the column which allow for the withdrawal of different fractions or products having different boiling points or boiling ranges. By increasing the temperature of the product inside the columns, the different products are separated. The "lightest" products (those with the lowest boiling point) exit from the top of the columns and the "heaviest" products (those with the highest boiling point) exit from the bottom of the column.

For example, fractional distillation is used in oil refineries to separate crude oil into useful substances (or fractions) having different hydrocarbons of different boiling points. The crude oil fractions with higher boiling points:

Large-scale industrial towers use reflux to achieve a more complete separation of products. Reflux refers to the portion of the condensed overhead liquid product from a distillation or fractionation tower that is returned to the upper part of the tower as shown in the schematic diagram of a typical, large-scale industrial distillation tower. Inside the tower, the reflux liquid flowing downwards provides the cooling needed to condense the vapors flowing upwards, thereby increasing the effectiveness of the distillation tower. The more reflux is provided for a given number of theoretical plates, the better the tower's separation of lower boiling materials from higher boiling materials. Alternatively, the more reflux provided for a given desired separation, the fewer theoretical plates are required.

Fractional distillation is also used in air separation, producing liquid oxygen, liquid nitrogen, and highly concentrated argon. Distillation of chlorosilanes also enable the production of high-purity silicon for use as a semiconductor.

In industrial uses, sometimes a packing material is used in the column instead of trays, especially when low pressure drops across the column are required, as when operating under vacuum. This packing material can either be random dumped packing (1-3 in (25-76 mm) wide) such as Raschig rings or structured sheet metal. Typical manufacturers are Koch, Sulzer and other companies. Liquids tend to wet the surface of the packing and the vapors pass across this wetted surface, where mass transfer takes place. Unlike conventional tray distillation in which every tray represents a separate point of vapor liquid equilibrium the vapor liquid equilibrium curve in a packed column is continuous. However, when modeling packed columns it is useful to compute a number of "theoretical plates" to denote the separation efficiency of the packed column with respect to more traditional trays. Differently shaped packings have different surface areas and porosity. Both of these factors affect packing performance.

Design of industrial distillation columns

Design and operation of a distillation column depends on the feed and desired products. Given a simple, binary component feed, analytical methods such as the McCabe-Thiele method or the Fenske equation can be used. For a multi-component feed, simulation models are used both for design and operation.

Moreover, the efficiencies of the vapor-liquid contact devices (referred to as plates or trays) used in distillation columns are typically lower than that of a theoretical 100% efficient equilibrium stage. Hence, a distillation column needs more plates than the number of theoretical vapor-liquid equilibrium stages.

Reflux refers to the portion of the condensed overhead product that is returned to the tower. The reflux flowing downwards provides the cooling required for condensing the vapours flowing upwards. The reflux ratio, which is the ratio of the (internal) reflux to the overhead product, is conversely related to the theoretical number of stages required for efficient separation of the distillation products. Fractional distillation towers or columns are designed to achieve the required separation efficiently. The design of fractionation columns is normally made in two steps; a process design, followed by a mechanical design. The purpose of the process design is to calculate the number of required theoretical stages and stream flows including the reflux ratio, heat reflux and other heat duties. The purpose of the mechanical design, on the other hand, is to select the tower internals, column diameter and height. In most cases, the mechanical design of fractionation towers is not straightforward. For the efficient selection of tower internals and the accurate calculation of column height and diameter, many factors must be taken into account. Some of the factors involved in design calculations include feed load size and properties and the type of distillation column used.

The two major types of distillation columns used are tray and packing columns. Packing columns are normally used for smaller towers and loads that are corrosive or temperature sensitive or for vacuum service where pressure drop is important. Tray columns, on the other hand, are used for larger columns with high liquid loads. They first appeared on the scene in the 1820s. In most oil refinery operations, tray columns are mainly used for the separation of petroleum fractions at different stages of oil refining.

In the oil refining industry, the design and operation of fractionation towers is still largely accomplished on an empirical basis. The calculations involved in the design of petroleum fractionation columns require in the usual practice the use of numerable charts, tables and complex empirical equations. In recent years, however, a considerable amount of work has been done to develop efficient and reliable computer-aided design procedures for fractional distillation.

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Fractional distillation is the separation of a mixture into its component parts, or fractions. Chemical compounds are separated by heating them to a temperature at which one or more fractions of the mixture will vaporize. It uses distillation to fractionate.

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Plastics may be the most polarizing material of modern times. It provides a series of incredible benefits that help us every day, but the product can also be one of the most harmful substances on our planet. It was a word that originally meant the product was pliable and easily shaped. It is only recent definitions that now have the term apply to a variety of polymers.

The first plastic product came about because of the research performed by John Wesley Hyatt in 1869. He invented the first synthetic polymer in an effort to claim a $10,000 prize that was announced as a way to provide a substitute for ivory. Billiards was growing in popularity in the United States, and the original balls were made from wild elephant tusks. Hyatt discovered that by treating cotton fiber cellulose with camphor, a product that could be crafted into a variety of shapes became possible.

This original celluloid received immediate praise as the savior of elephants and tortoises. We felt like we could protect the natural world from the human's destructive need to consume. As new polymers went into the development process, the plastics advantages and disadvantages required constant review to avoid detrimental environmental impacts.

List of the Advantages of Plastics

1. Many plastics have a long lifespan that encourages reuse.
Plastics don't need to be a single-use product or be treated as disposable. Many forms of this material have a long lifespan that is equal to or greater than what other materials provided. A well-made and maintained PVC pipe has the capability of providing service for up to a century. Construction plastics have an average lifespan of 35 years. When we continue to use these items instead of throwing them away, then we can promote a lower waste rate instantly.

If you reuse plastic items at least seven times, then you're saving just as many energy resources than if you'd recycled the product.

2. Plastic production methods compare favorably to many other materials.
The plastics manufacturing process can be energy-intensive with fossil fuels, but it is still a resource that is more environmentally friendly than other materials. Bamboo provides natural fibers to use, although manufacturers must use chemical processes to turn the content into something useable. Aluminum is another example of a product that plastic beats with this advantage.

Recycling processes can change the comparison at times. It is still a clear advantage that plastics can provide when consistent reuse occurs. Even if you choose a fabric bag over a plastic one, you must use the reusable bag at least 40 times before you're matching the environmental footprint of a similar plastic product. Conventional cotton bags require 7,100 uses before creating a neutral investment.

3. Plastics take up less space in our landfills.
Even though it can take a significant amount of time for plastic materials to break down in a landfill, the amount of space that it takes up in these waste disposal areas is minimal when compared to other items. Paper products take up seven times more volume. When we can divert these items toward recycling programs or other uses, then we can start managing our landfill areas more effectively.

4. Methane doesn't form when plastics start decomposing.
Organic materials release greenhouse gases when they start decomposing. The focus of this process is often on carbon dioxide, but the methane that gets emitted is extremely problematic. When compared to CO2, methane is up to 20 times more potent as a reflecting atmospheric product.

Plastics don't emit this gas when it starts breaking down, which means it is easier to calculate the total lifecycle impact of the product.

5. It provides a safe way to transport our needed items.
One of the reasons why we use plastics for bottles that contain water and other beverages is because it keeps the product safe. We use the material to quickly and affordably get water to vulnerable populations all over the world. If a city experiences a shortage or emergency supplies are necessary after a natural disaster, we use this product to ensure that people can have their needs met.

Certain types of plastic were found to be potentially harmful with this advantage in the past, so legislative bans were put into place to prevent their use.

6. We have multiple ways to manage plastic waste.
Heat is one of the most common methods used to process plastic waste or create recycling opportunities. It isn't the only option that's available to use today. We can use pyrolysis or gasification to process this material with minimal emissions or pollution. It is even possible to shred the materials to create new fabrics from them.

Although the cost of the alternative processing methods isn't economically sustainable in some communities, this advantage is still present and worth considering. Some plastic bottles are even more eco-friendly than other materials when measured across several environmental indicators.

7. Plastics contain a high energy density to consider.
Incinerating plastics can be quite useful in some situations because of its high energy density rating. This material offers a significant energy output for cement kilns or incineration because we create it with the use of petroleum hydrocarbons. That means we can use it as a direct replacement for fossil fuel combustion since the foundation of the product comes from an energy resource that we all use.

The paper products sector in the United Kingdom uses almost the same amount of energy as the plastics and rubber industries. That's how useful this material can be from an energy standpoint.

8. Plastics are an affordable material.
We can keep costs down for a variety of items because of the low price point that's available for plastics. Our established manufacturing processes allow us to create several million tons of this material for a variety of purposes, ranging from packaging to straws. We can modify the chemistry of the material to provide specific beneficial properties for its end use, including the option to make it softer, harder, malleable, or durable.

9. The plastics industry is a significant contributor to the global economy.
The global plastic industry creates a market worth over $1 trillion annually. Almost two million people have direct employment opportunities in the United States because of this invention. We use it to prevent food waste, protect our health, and promote better hygiene. We have construction-grade and industrial plastics to use. It's essential for modern transportation, provides infrastructure support, and makes the delivery and transport of items cheaper and easier to complete.

Over 31,000 people in the United States are directly employed in the manufacturing of plastic bags. The plastics industry in the U.S. is currently the eighth-largest one presently operating.

List of the Disadvantages of Plastics

1. Plastics typically come from non-renewable resources.
Although the first plastic materials came from plant-based fibers, most of the items that we produce today have fossil fuels as their foundation. It's usually petroleum, but we can also use natural gas to develop this product. About 4% of these fuels goes directly into the plastics industry to create new products. When we look at the number of resources consumed during the refinement process and the expected rise in demand, the fossil fuel cost of plastics could reach 20% within the next decade.

2. The majority of the pollution found in the world's oceans is plastic.
Up to 80% of all marine debris contains plastic. This problem comes from land and marine sources, often collecting in large areas of open water where currents come together. This issue causes us to find waste on beaches, on land, and even in freshwater sources. Some of the items that get littered most often are plastic straws, stirrers, bottles, lids, and food wrappers.

Removing plastic pollution from ocean surface water comes at the cost of $5 per kilogram, but the item's reuse value is only $0.30. That's why the effort to clean up marine areas is being led by non-profit agencies.

3. Plastic pollution can lead to several economic losses.
Plastic packaging pollution by itself creates an economic loss of almost $80 billion to the global economy annually. It makes up nearly 50% of all waste from this industry, and virtually every other industry uses the item in some way. Building and construction plastics represent 16% of plastic use, while textiles are responsible for about 15%. Since it isn't profitable to recycle many of the items, more of it tends to go into waste streams instead of reuse.

The global average for plastic recycling is about 14%. India is one of the world's leaders by recycling approximately 60% of its items, while the United States comes in close to last in the developed world by recycling only 9%.

4. We cannot infinitely recycle plastic products.
Metals can be recycled numerous times into a variety of different products because of the properties of the material. Plastics don't share that opportunity. We can only reuse or recover it a specific number of times before it loses its quality and integrity. That means we are more likely to down-cycle this product, incinerate it, or stash it in a landfill.

Some plastic products and items can't be recycled at all, furthering the impact of this disadvantage. Over 93 billion plastic products don't get touched each year, which means they enter into our waste streams.

5. We must spend energy to clean plastics to recycle items.
Plastics that have cross-contamination with different types create unusable products. We also need to have the items cleaned before recyclers can turn the things into new pieces.

Some products contain different plastic types in the same item (i.e. a bottle and a lid), creating even more challenges to manage. It's a disadvantage that makes recycling inefficient at best for some communities - and sometimes impossible.

6. The re-sell chains for recycled plastic are long and challenging to manage.
Some recycling processing and re-sell chains for plastics tend to be long and inefficient. One item might change hands several times or travel a long distance to go through the recycling process. When it takes that much energy to reuse or recycle a product, then many of the potential benefits disappear. That's why some plastics have a high waste rate, especially if they aren't #1 or #2 options.

This disadvantage is one of the primary reasons why plastic is one of the most common materials found in municipal waste centers and landfills.

7. It takes a long time for plastic products to decompose.
Plastic takes a long time to degrade when compared to organic items. A plastic fishing line might take over 600 years to finally break down. Some researchers believe that some forms of this material might never fully decompose, remaining as nano plastics that could influence human, animal, and marine health in a variety of ways.

Even the plastic bags that we use to carry items every day can take 10 to 20 years to decompose naturally - but some of them can take up to an estimated 1,000 years. When you throw away a plastic water bottle, then it could take 450 years.

8. Plastics harm our ocean environments.
EcoWatch estimates that 10 metric tons of plastic products, including grocery bags, will wash out to the ocean from Los Angeles every day. Those items break down into small fragments that become microscopic in size and consumed by marine life. Up to 24,000 tons of plastic contaminate our food chain each year. Up to 25% of the fish sold in California markets contained fibrous or whole plastic in the animal's stomach. The chemicals from the plastic that leeches into these animals could possibly transfer to humans upon consumption.
Conclusion
Plastic is arguably the most revolutionary product in the history of humanity. It gives us a variety of ways to improve the safety of our foods and beverages while providing support mechanisms that create infrastructure benefits that we all use.

We have also discovered that endocrine disruptors are the link between plastic and human health hazards. PCBs and dioxins have already polluted the world's waterways. BPA, or bisphenol A, is specifically banned because of this trait - although people still receive exposure to it from a variety of sources. The CDC estimates that 95% of people have BPA contamination in their bodies.

When we look at these plastics advantages and disadvantages, it is imperative to remember that ingestion is not the only danger to consider. Simple exposures, the time it takes to decompose, and the litter we create are damaging our planet. We must increase our recycling rates and look for alternatives when it makes sense to decrease our exposure levels.

About the Author
Brandon Miller has a B.A. from the University of Texas at Austin. He is a seasoned writer who has written over one hundred articles, which have been read by over 500,000 people. If you have any comments or concerns about this blog post, then please contact the Green Garage team here.

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17 Biggest Advantages and Disadvantages of Plastics

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Plastics may be the most polarizing material of modern times. It provides a series of incredible benefits that help us every day, but the product can also be one of the most harmful substances on

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Carbon is one of the most fascinating elements in all of nature, with chemical and physical properties unlike any other element. With just six protons in its nucleus, it's the lightest abundant element capable of forming a slew of complex bonds. All known forms of life are carbon-based, as its atomic properties enable it to link up with up to four other atoms at a time. The possible geometries of those bonds also enable carbon to self-assemble, particularly under high pressures, into a stable crystal lattice. If the conditions are just right, carbon atoms can form a solid, ultra-hard structure known as a diamond.

Although diamonds commonly known as the hardest material in the world, there are actually six materials that are harder. Diamonds are still one of the hardest naturally occurring and abundant materials on Earth, but these six materials all have it beat.

Honorable mention: there are three terrestrial materials that aren't quite as hard as diamond is, but are still remarkably interesting for their strength in a variety of fashions. With the advent of nanotechnology - alongside the development of nanoscale understandings of modern materials - we now recognize that there are many different metrics to evaluate physically interesting and extreme materials.

On the biological side, spider silk is notorious as the toughest. With a higher strength-to-weight ratio than most conventional materials like aluminum or steel, it's also remarkable for how thin and sticky it is. Of all the spiders in the world, Darwin's bark spiders have the toughest: ten times stronger than kevlar. It's so thin and light that approximately a pound (454 grams) of Darwin's bark spider silk would compose a strand long enough to trace out the circumference of the entire planet.

For a naturally occurring mineral, silicon carbide - found naturally in the form of moissanite - is only slightly less in hardness than diamonds. (It's still harder than any spider silk.) A chemical mix of silicon and carbon, which occupy the same family in the periodic table as one another, silicon carbide grains have been mass produced since 1893. They can be bonded together through a high-pressure but low-temperature process known as sintering to create extremely hard ceramic materials.

These materials are not only useful in a wide variety of applications that take advantage of hardness, such as car brakes and clutches, plates in bulletproof vests, and even battle armor suitable for tanks, but also have incredibly useful semiconductor properties for use in electronics.

Tiny silica spheres, from 50 nanometers in diameter down to just 2 nanometers, were created for the first time some 20 years ago at the Department of Energy's Sandia National Laboratories. What's remarkable about these nanospheres is that they're hollow, they self-assemble into spheres, and they can even nest inside one another, all while remaining the stiffest material known to humankind, only slightly less hard than diamonds.

Self-assembly is an incredibly powerful tool in nature, but biological materials are weak compared to synthetic ones. These self-assembling nanoparticles could be used to create custom materials with applications from better water purifiers to more efficient solar cells, from faster catalysts to next-generation electronics. The dream technology of these self-assembling nanospheres, though, is printable body armor, custom to the user's specifications.

Diamonds, of course, are harder than all of these, and still clock in at #7 on the all-time list of hardest materials found or created on Earth. Despite the fact that they've been surpassed by both other natural (but rare) materials and synethetic, human-made ones, they do still hold one important record.

Diamonds remain the most scratch-resistant material known to humanity. Metals like titanium are far less scratch-resistant, and even extremely hard ceramics or tungsten carbide cannot compete with diamonds in terms of hardness or scratch-resistance. Other crystals that are known for their extreme hardness, such as rubies or sapphires, still fall short of diamonds.

But six materials have even the vaunted diamond beat in terms of hardness.

6.) Wurtzite boron nitride. Instead of carbon, you can make a crystal out of a number of other atoms or compounds, and one of them is boron nitride (BN), where the 5th and 7th elements on the periodic table come together to form a variety of possibilities. It can be amorphous (non-crystalline), hexagonal (similar to graphite), cubic (similar to diamond, but slightly weaker), and the wurtzite form.

The last of these forms is both extremely rare, but also extremely hard. Formed during volcanic eruptions, it's only ever been discovered in minute quantities, which means that we've never tested its hardness properties experimentally. However, it forms a different kind of crystal lattice - a tetrahedral one instead of a face-centered cubic one - that is 18% harder than diamond, according to the most recent simulations.

5.) Lonsdaleite. Imagine you have a meteor full of carbon, and therefore containing graphite, that hurtles through our atmosphere and collides with planet Earth. While you might envision a falling meteor as incredibly hot body, it's only the outer layers that become hot; the insides remain cool for most (or even, potentially, all) of their journey towards Earth.

Upon impact with Earth's surface, however, the pressures inside become larger than any other natural process on our planet's surface, and cause the graphite to compress into a crystalline structure. It doesn't possess the cubic lattice of a diamond, however, but a hexagonal lattice, which can actually achieve hardnesses that are 58% greater than what diamonds achieve. While real examples of Lonsdaleite contain sufficient impurities to make them softer than diamonds, an impurity-free graphite meteorite striking the Earth would undoubtedly produce material harder than any terrestrial diamond.

. From hereon out, we leave the realm of naturally occurring substances behind. Dyneema, a thermoplastic polyethylene polymer, is unusual for having an extraordinarily high molecular weight. Most molecules that we know of are chains of atoms with a few thousand atomic mass units (protons and/or neutrons) in total. But UHMWPE (for ultra-high-molecular-weight polyethylene) has extremely long chains, with a molecular mass in the millions of atomic mass units.

With very long chains for their polymers, the intermolecular interactions are substantially strengthened, creating a very tough material. It's so tough, in fact, that it has the highest impact strength of any known thermoplastic. It has been called the strongest fiber in the world, and outperforms all mooring and tow ropes. Despite being lighter than water, it can stop bullets and has 15 times the strength of a comparable amount of steel.

3.) Palladium microalloy glass. It's important to recognize that there are two important properties that all physical materials have: strength, which is how much force it can withstand before it deforms, and toughness, which is how much energy it takes to break or fracture it. Most ceramics are strong but not tough, shattering with vice grips or even when dropped from only a modest height. Elastic materials, like rubber, can hold a lot of energy but are easily deformable, and not strong at all.

Most glassy materials are brittle: strong but not particularly tough. Even reinforced glass, like Pyrex or Gorilla Glass, isn't particularly tough on the scale of materials. But in 2011, researchers developed a new microalloy glass featuring five elements (phosphorous, silicon, germanium, silver and palladium), where the palladium provides a pathway for forming shear bands, allowing the glass to plastically deform rather than crack. It defeats all types of steel, as well as anything lower on this list, for its combination of both strength and toughness. It is the hardest material to not include carbon.

2.) Buckypaper. It is well-known since the late 20th-century that there's a form of carbon that's even harder than diamonds: carbon nanotubes. By binding carbon together into a hexagonal shape, it can hold a rigid cylindrical-shaped structure more stably than any other structure known to humankind. If you take an aggregate of carbon nanotubes and create a macroscopic sheet of them, you can create a thin sheet of them: buckypaper.

Each individual nanotube is only between 2 and 4 nanometers across, but each one is incredibly strong and tough. It's only 10% the weight of steel but has has hundreds of times the strength. It's fireproof, extremely thermally conductive, possesses tremendous electromagnetic shielding properties, and could lead to materials science, electronics, military and even biological applications. But buckypaper cannot be made of 100% nanotubes, which is perhaps what keeps it out of the top spot on this list.

1.) Graphene. At last: a hexagonal carbon lattice that's only a single atom thick. That's what a sheet of graphene is, arguably the most revolutionary material to be developed and utilized in the 21st century. It is the basic structural element of carbon nanotubes themselves, and applications are growing continuously. Currently a multimillion dollar industry, graphene is expected to grow into a multibillion dollar industry in mere decades.

In proportion to its thickness, it is the strongest material known, is an extraordinary conductor of both heat and electricity, and is nearly 100% transparent to light. The 2010 Nobel Prize in Physics went to Andre Geim and Konstantin Novoselov for groundbreaking experiments involving graphene, and the commercial applications have only been growing. To date, graphene is the thinnest material known, and the mere six year gap between Geim and Novoselov's work and their Nobel award is one of the shortest in the history of physics.

The quest to make materials harder, stronger, more scratch-resistant, lighter, tougher, etc., is probably never going to end. If humanity can push the frontiers of the materials available to us farther than ever before, the applications for what becomes feasible can only expand. Generations ago, the idea of microelectronics, transistors, or the capacity to manipulate individual atoms was surely exclusive to the realm of science-fiction. Today, they're so common that we take all of them for granted.

As we hurtle full-force into the nanotech age, materials such as the ones described here become increasingly more important and ubiquitous to our quality of life. It's a wonderful thing to live in a civilization where diamonds are no longer the hardest known material; the scientific advances we make benefit society as a whole. As the 21st century unfolds, we'll all get to see what suddenly becomes possible with these new materials.

... Read More

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There Are 6 'Strongest Materials' On Earth That Are Harder Than Diamonds

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Carbon is one of the most fascinating elements in all of nature, with chemical and physical properties unlike any other element. With just six protons in its nucleus, it's the lightest abundant element capable of forming a slew of complex bonds.

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Density is defined as the ratio of the mass of an object to the volume of space the object takes up. Mathematically, we would say D = M/V. Density will determine if you sink or float when put into a liquid, like water.

Take 8 same-size plastic Easter eggs that come apart ( so you can fill them). This gives you 8 equal volumes. To determine the volume of your egg, fill it completely with water (top and bottom) and then pour the water into a graduated cylinder. For water, 1 mL = 1 cm ³. (For example, our eggs held 70 mL of water, so the volume of the egg was 70 cm ³.) To create the average densities of the 8 planets in our solar system, we just need to fill the eggs with the right amount of material so they have the correct mass for the given volume. The average densities for each planet and the required mass for a 70 cm ³ egg are given in the Table below. Remember, Required Mass = Average Density multiplied by Egg Volume, so if your eggs have a different volume than 70 cm ³, just multiply the average densities in the Table by your egg volume to find the required masses for each of your eggs. Small lead balls (such as lead shot or BBs) work best as a filler!

Now you are ready to drop all 8 eggs in a giant tub of water and see what happens!

Explanation: If the density of the object is less than that of the water (which is 1 gm per cubic cm), the object floats. If density is greater, the object sinks. Saturn is mainly composed of the lightest two gases known, hydrogen and helium. It is the only planet in our solar system whose density is less than water. So Saturn will float while all the other planets sink!

This activity is part of the StarChild site.
http://starchild.gsfc.nasa.gov/

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Density is defined as the ratio of the mass of an object to the volume of space the object takes up. Mathematically, we would say D = M/V. Density will determine if you sink or float when put into a liquid, like water.

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A solar filter dimmed true-color image of the visible photosphere of the Sun

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What do you see in your mind when you think of a diamond? If you're like most of us, you think of a gem that's perfect in every way - right down to its signature shape. What you probably don't realize, however, is that diamonds aren't perfect when they're plucked from the mines. These rough diamonds are then cut into the styles we know and love.
View Diamond Catalog
Diamonds are graded based on the 4 Cs - including cut - but the actual step-by-step process of how its done is pretty much a mystery to most of us. How are diamonds cut exactly? Let's break it down.

Diamonds are cut in two ways

Fun fact: Diamonds can only be cut with diamonds. The reason? Diamonds are some of the hardest materials on earth, so the tools they use to do it are usually diamond bladed on the edges or have an edge of diamond dust.

But before they're cut, a master diamond cutter evaluates the stone for its inclusions - AKA flaws - and carat weight. From there, the cutter then determines whether it's shaped using a step cut or a brilliant cut.

Most of the time, a rough diamond is in a octahedron shape, meaning it has eight faces, twelve edges and six vertices. In plain English: It's the perfect shape for a brilliant cut because it won't lose too much carat weight in the process - and it'll shine brightly in the light.

A step cut is typically done on a diamond to create a square or rectangular shape that features eight lines running parallel along both the length and width of the diamond, drawing the eye to the center of the stone and give the illusion that it has "steps," hence the name. While step cut diamonds don't shine as brightly as brilliant cut diamonds, they are typically clearer.

The actual diamond-cutting process

So, how are diamonds cut? It's a complicated process that's typically broken down into five steps by a qualified diamond expert: planning, cleaving, bruting, polishing and inspecting.

Planning. The first step is almost always the most important - and that's especially true for diamond cutting. Planning a diamond cut determines so much of how a diamond turns out because a number of details, including shape and size, is decided at this point. The diamond cutter uses his or her expert knowledge, along with computer software, to map the rough diamonds to help make it the best it can be (without sacrificing too much of the diamond in the process).

Cleaving. In this step, the diamond cutting expert splits the rough diamond into separate pieces. Cleaving is typically done with mechanical saws or contactless lasers to keep the diamond in tip-top shape.

Bruting. Also called girdling, bruting takes the separated rough diamonds and turns them into round stones by placing them on a spinning axle and grinding them against each other to create the rough finish.

Polishing. This is technically a two-step process that involves taking the round shape and turning it into a diamond, complete with the smooth and reflective facets we know and love in our diamonds. The first step of polishing, blocking, involves creating the pavilions, crowns, cutets and facets of the diamond. This creates the base for the next stage, brillianteering. During this process, the diamond's remaining facets are added, then the brilliance and fire of the diamond is decided.

Inspecting. Though it sounds similar, the diamond cut inspecting process is not the same as diamond grading. Instead, this step involves thoroughly checking the diamond to make sure it meets the right specifications. If it does, it's passed on and eventually sold. If not, it's sent back to polishing for touch-ups.

What happens after a diamond is cut?

Once a diamond is cut, it's then sent to gem experts to receive a grade based on its 4 Cs - including the cut.

While you can buy diamonds without a grade, it's not the best choice. At With Clarity, every diamond we sell comes with a GIA grading report or an IGI grading report so you'll know everything about your diamond - and you can ensure you have what you paid for. Shop with confidence and with clarity.
Shop Certified Diamonds

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How Are Diamonds Cut? Using Other Diamonds - Here's How

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What do you see in your mind when you think of a diamond? If you're like most of us, you think of a gem that's perfect in every way - right down to its signature shape. What you probably don't realize, however, is that diamonds aren't perfect when they're plucked from the mines.

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Diamond cutting is the practice of shaping a diamond from a rough stone into a faceted gem. Cutting diamond requires specialized knowledge, tools, equipment, and techniques because of its extreme difficulty.

The first guild of diamond cutters and polishers (Diamantaire) was formed in 1375 in Nuremberg, Germany, and led to the development of various types of " cut". This has two meanings in relation to diamonds. The first is the shape: square, oval, and so on. The second relates to the specific quality of cut within the shape, and the quality and price will vary greatly based on the cut quality. Since diamonds are one of the hardest materials, special diamond-coated surfaces are used to grind the diamond down. The first major development in diamond cutting came with the "Point Cut" during the later half of the 14th century: the Point Cut follows the natural shape of an octahedral rough diamond crystal, eliminating some waste in the cutting process.

Diamond cutting, as well as overall processing, is concentrated in a few cities around the world. The main diamond trading centers are Antwerp, Tel Aviv, and Dubai from where roughs are sent to the main processing centers of India and China. Diamonds are cut and polished in Surat, India and the Chinese cities of Guangzhou and Shenzhen. India in recent years has held between 19-31% of the world market in polished diamonds and China has held 17% of the world market share in a recent year. Another important diamond center is New York City.

The basic diamond cutting process includes these steps; planning, cleaving or sawing, bruting, polishing, and final inspection. A simplified round brilliant cut process includes the following stages:

Planning - Modern day planning of a diamond is done using computer software.

Marking - Outlining the best possible shape and cut of the diamond.

Sawing the rough stone - depending on the shape of rough diamond as not all diamonds are sawn.

Table

Bruting the girdle.

Blocking 8 main pavilion facets - these facets are divided into 4 corners and 4 pavilions as the corners and pavilions run in different directions due to the atomic structure of the diamond.

Crown - the crown consist of 8 main facets and are divided into 4 corners and 4 Bezels.

Final bruting - ensuring the diamonds girdle is perfectly round and smooth.

Polishing all 16 main facets.

Brillianteering - Adding and polishing 8 stars and 16 pavilion and 16 crown halves.

Quality control - checking for symmetry, polish and cut (angles) after the diamond is completed.

This is just one, although a fairly common way of creating a round brilliant cut. The actual process also includes many more stages depending on the size and quality of the rough stone. For example, bigger stones are first scanned to get the three-dimensional shape, which is then used to find the optimal usage. The scanning may be repeated after each stage and bruting may be done in several steps, each bringing the girdle closer to the final shape.

It is possible only because the hardness of diamond varies widely according to the direction in which one is trying to cut or grind.

Diamond manufacturers analyze diamond rough from an economic perspective, with two objectives steering decisions made about how a faceted diamond will be cut. The first objective is that of maximum return on investment for the piece of diamond rough. The second is how quickly the finished diamond can be sold. Scanning devices are used to get a 3-dimensional computer model of the rough stone. Also, inclusions are photographed and placed on the 3D model, which is then used to find an optimal way to cut the stone.

Maximizing value

The process of maximizing the value of finished diamonds, from a rough diamond into a polished gemstone, is both an art and a science. The choice of cut is influenced by many factors. Market factors include the exponential increase in value of diamonds as weight increases, referred to as weight retention, and the popularity of certain shapes amongst consumers. Physical factors include the original shape of the rough stone, and location of the inclusions and flaws to be eliminated.

Weight retention

The weight retention analysis studies the diamond rough to find the best combination of finished stones as it relates to per carat value. For instance, a 2.20-carat (440 mg) octahedron may produce (i) either two half-carat (100 mg) diamonds whose combined value may be higher than that of (ii) a 0.80-carat (160 mg) diamond plus a 0.30-carat (60 mg) diamond that could be cut from the same rough diamond.

The round brilliant cut and square brilliant cuts are preferred when the crystal is an octahedron, as often two stones may be cut from one such crystal. Oddly shaped crystals, such as macles are more likely to be cut in a fancy cut -that is, a cut other than the round brilliant-which the particular crystal shape lends itself to.

Even with modern techniques, the cutting and polishing of a diamond crystal always results in a dramatic loss of weight, about 50%. Sometimes the cutters compromise and accept lesser proportions and symmetry in order to avoid inclusions or to preserve the weight. Since the per-carat price of a diamond shifts around key milestones (such as 1.00 carat), many one-carat (200 mg) diamonds are the result of compromising cut quality for carat weight.

Color retention

In colored diamonds, cutting can influence the color grade of the diamond, thereby raising its value. Certain cut shapes are used to intensify the color of the diamond. The radiant cut is an example of this type of cut.

Natural green color diamonds most often have merely a surface coloration caused by natural irradiation, which does not extend through the stone. For this reason green diamonds are cut with significant portions of the original rough diamond's surface ( naturals) left on the finished gem. It is these naturals that provide the color to the diamond.

Turnaround minimization

The other consideration of diamond planning is how quickly a diamond will sell. This consideration is often unique to the type of manufacturer. While a certain cutting plan may yield a better value, a different plan may yield diamonds that will sell sooner, providing an earlier return on the investment.

Cleaving is the separation of a piece of diamond rough into separate pieces, to be finished as separate gems. During the planning stage, diamond manufacturers identify cleavage planes, and use those planes to decide how to split the diamond. Diamond manufacturers cut a groove in the diamond with a laser or saw, and then split the diamond with a steel blade.

Sawing is the use of a diamond saw or laser to cut the diamond rough into separate pieces. Unlike cleaving, this step does not involve cleavage planes. This step gives diamonds their initial shape.

Bruting is the art of cutting a diamond round. In the modern era diamonds are rounded using either a laser, a diamond disk impregnated with diamonds, or two diamonds cutting against each other. Industrial diamonds can also be used for bruting a diamond round. Modern computer software measures the roundness of each diamond and ideal cut diamonds have to round within a tenth of a millimeter to qualify as an excellent cut diamond.

Diamond polishing is the final polishing of the diamond. In a diamond factory, one would find a diamond crossworker who first places the main facets on a diamond (blocking the diamond). This is done to ensure maximum weight, clarity and best angles for the specific shape of diamond. After initial crossworking is complete, the diamond is finalized by smoothing the main facets by the crossworker, which is known as polishing the diamond. After the main facets have been polished by the crossworker, the final facets are polished onto the diamond by a brillianteer. The facets added are the stars, top and bottom halves are also known as upper and lower girdle facets.

The final stage involves thoroughly cleaning the diamond in acids, and examining the diamond to see whether it meets the quality standards of the manufacturer.

Due to changes in market desirability and popularity, the value of different styles of diamond fluctuates. All diamonds can be recut into new shapes that will increase value at that time in the market and desirability. An example of this is the marquise cut diamond which was popular in the 1970s to 1980s. In later decades, jewelers had little success in selling this shape in comparison to other shapes like the oval or pear shape.[citation needed ] The marquise can be cut into an oval diamond by any diamond cutter with a loss of 5 to 10% in total weight.[citation needed ] For example, a 1.10-carat marquise shape would be a 1.00 oval cut diamond by rounding the sharp points and creating an oval which currently in the market has a much greater desirability and resale value. The same marquise shape also could become a pear shape instead by only trimming and rounding the side which will be turned into the base of the pear shape.

In the 18th century there was a trend for recutting Indian diamonds to suit English tastes. The Koh-i-Noor's original cut weighed a little over 186.00 carats. When it was recut to an oval-shaped brilliant, almost 80 carats were lost.[citation needed ]

Other aspects are affected in recutting for value as well, such as the clarity. If an original shape contained inclusions on the tips, the recut would yield an increase in clarity since trimming down to a new shape would yield a cleaner overall finished diamond.[citation needed ]

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Diamond cutting is the practice of shaping a diamond from a rough stone into a faceted gem. Cutting diamond requires specialized knowledge, tools, equipment, and techniques because of its extreme difficulty. The first guild of diamond cutters and polishers (Diamantaire) was formed in 1375 in Nuremberg, Germany, and led to the development of various types of " cut".

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The melting point is the temperature at which the vapour pressure of the solid and the liquid are the same and the presssure totals one atmosphere.

Image showing periodicity of the chemical elements for melting point in a periodic table cityscape style.

Image showing periodicity of the chemical elements for melting point in a periodic table heatscape style.

Image showing periodicity of the chemical elements for melting point in a spiral periodic table heatscape style.

Image showing periodicity of the chemical elements for melting point in a 3D spiral periodic table column style.

Image showing periodicity of the chemical elements for melting point in a 3D periodic table column style.

Units

K (Kelvin)

Notes

Other temperature scales include the centigrade (Celsius) scale and the Fahrenheit scale. The size of one degree is the same on the Kelvin scale (K) as on the centigrade scale (°C). The zero point is different:

temperature (K) = temperature (°C) + 273.15

Thus, the melting point of water is = 0°C = 273.15 K and the boiling point of water is = 100°C = 373.15 K

On the Fahrenheit scale (°F), the melting point of water = 32°F while the boiling point = 212°F.

Therefore the degree size is different on the Fahrenheit scale with 180 Fahrenheit degrees = 100 centigrade degrees. Conversion between centigrade and Fahrenheit is achieved using the following relationship:

temperature (°C) = [temperature (°F) -32] * 5/9

You can look at visual representations of melting points, boiling points, and the liquid range using the following links.

Literature sources

1. A.M. James and M.P. Lord in Macmillan's Chemical and Physical Data, Macmillan, London, UK, 1992.

2. G.W.C. Kaye and T.H. Laby in Tables of physical and chemical constants, Longman, London, UK, 15th edition, 1993.

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Mark Winter, University of Sheffield and WebElements Ltd

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The melting point is the temperature at which the vapour pressure of the solid and the liquid are the same and the presssure totals one atmosphere. K (Kelvin) Other temperature scales include the centigrade (Celsius) scale and the Fahrenheit scale. The size of one degree is the same on the Kelvin scale (K) as on the centigrade scale (°C).

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The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as visible light and infrared radiation. It is by far... Wikipedia

Names : Sun, Sol /ˈsɒl/, Helios /ˈhiːliəs/

Surface area : 6.09×10 ¹² km ²; 12,000 × Earth

Escape velocity (from the surface) : 617.7 km/s; 55 × Earth

Equatorial surface gravity : 274 m/s ²; 28 × Earth

Mean radiance (Isol) : 2.009×10 ⁷ W·m −2·sr −1

Center density (modeled) : 162.2 g/cm ³; 12.4 × Earth

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Please click here if you are not redirected within a few seconds. The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy mainly as visible light and infrared radiation.

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(Image credit: George Garcia)

Earth's moon is the brightest object in our night sky. It appears quite large, but that is only because it is the closest celestial body. The moon is a bit more than one-fourth (27 percent) the size of Earth, a much larger ratio (1:4) than any other planets and their moons. Earth's moon is the fifth largest moon in the solar system.

The moon's mean radius is 1,079.6 miles (1,737.5 kilometers). Double those figures to get its diameter: 2,159.2 miles (3,475 km), less than a third the width of Earth. The moon's equatorial circumference is 6,783.5 miles (10,917 km).

"If Earth were the size of a nickel, the moon would be about as big as a coffee bean," according to NASA.

The moon's surface area is about 14.6 million square miles (38 million square kilometers), which is less than the total surface area of the continent of Asia (17.2 million square miles or 44.5 million square km).

Mass, density and gravity

The moon's mass is 7.35 x 10 ²² kg, about 1.2 percent of Earth's mass. Put another way, Earth weighs 81 times more than the moon. The moon's density is 3.34 grams per cubic centimeter (3.34 g/cm ³). That is about 60 percent of Earth's density. The moon is the second densest moon in the solar system; Jupiter's moon Io is denser, with 3.53 g/cm ³.

The moon's gravitational force is only about 16.6 percent of Earth's gravity. A 45-kilogram person would weigh 100 lbs. on Earth but only 16.6 lbs. on the moon. A person who can jump up 10 feet on Earth would be able to jump almost 60 feet on the moon.

Like most of the solar system worlds, the moon's gravity varies based on its surface features. In 2012, NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission mapped the moon's gravity in unprecedented detail.

"What this map tells us is that more than any other celestial body we know of, the moon wears its gravity on its sleeve," GRAIL principle investigator Maria Zuber of the Massachusetts Institute of Technology said in a statement. "When we see a notable change in the gravity field, we can sync up this change with surface topography features such as craters, rilles or mountains."

While the moon is the closest and one of the longest studied astronomical objects, scientists continue to press the celestial body for details.

"The moon is the Rosetta Stone by which we understand the rest of the solar system," Noah Petro, deputy project scientist for NASA's Lunar Reconnaissance Orbiter (LRO) mission, said in a statement.

Super moon

Because the moon's orbit is not circular, it is sometimes closer than at other times. Perigee is the term for when the moon is closest to Earth. When a full moon coincides with perigee, we get a supermoon, which appears 14 percent larger and 30 percent brighter than usual. First applied by astrologer Richard Nolle in 1979, "supermoon" originally referred to a new or full moon that occurs when the moon is within 90 percent of its closest approach to Earth. The astronomical term for the phenomena is perigee-syzygy moon.

The difference isn't always obvious; according to NASA, "A 30 percent difference in brightness can be easily masked by clouds or the competing glare of urban lights." [ Infographic: How the 'Supermoon' Looks]

"The main reason why the orbit of the moon is not a perfect circle is that there are a lot of tidal, or gravitational, forces that are pulling on the moon," Petro told Space.com, adding that the gravity of the Earth, sun and planets of our solar system all impact the orbit of the moon. "You have all of these different gravitational forces pulling and pushing on the moon, which gives us opportunities to have these close passes."

A supermoon occurs about every 414 days. That's an average, however; the year 2016 boasted not one but three supermoons. The moon won't get as close to Earth as it got during the November 2016 supermoon until November 25, 2034.

The year 2017 only has one supermoon, which will occur on December 3, 2017. The year 2018 will have two supermoons, both in January, with the first on January 2 and the second on January 31. (The January 31 supermoon will also occur during a lunar eclipse.)

Horizon illusion

A little-understood optical effect can make the moon seem bigger when rising behind distant objects on the horizon. This trick of the brain - known either as the moon illusion or the Ponzo illusion - has been observed since ancient times, but still has no generally accepted explanation.

One theory holds that we're used to seeing clouds just a few miles above us, while we know that clouds on the horizon can be tens of miles distant. If a cloud on the horizon is the same size as clouds normally are overhead despite its great distance, we know it must be huge. And because the moon near the horizon is the same size as it normally is overhead, our brains automatically tack on a similar size increase.

But not everyone thinks clouds have worked their magic on our brains to such a great extent. One alternative hypothesis holds that the moon seems larger near the horizon because we can compare its size to nearby trees and other objects on Earth - and it looms large in comparison. Overhead, amid the vast expanse of outer space, the moon seems diminutive.

One way to test whether it's just an illusion is to hold your thumb up next to the moon and compare the moon's size with your thumbnail. When the moon is higher in the sky, look at it again; the moon will be the same size compared to your thumbnail.
Additional reporting by Nola Taylor Redd, Space.com contributor
Additional resources
Editor's note: This article was corrected to give Io back to its proper planet, Jupiter.

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(Image credit: George Garcia) Earth's moon is the brightest object in our night sky. It appears quite large, but that is only because it is the closest celestial body. The moon is a bit more than one-fourth (27 percent) the size of Earth, a much larger ratio (1:4) than any other planets and their moons.

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Plastics may be the most polarizing material of modern times. It provides a series of incredible benefits that help us every day, but the product can also be one of the most harmful substances on our planet. It was a word that originally meant the product was pliable and easily shaped. It is only recent definitions that now have the term apply to a variety of polymers.

The first plastic product came about because of the research performed by John Wesley Hyatt in 1869. He invented the first synthetic polymer in an effort to claim a $10,000 prize that was announced as a way to provide a substitute for ivory. Billiards was growing in popularity in the United States, and the original balls were made from wild elephant tusks. Hyatt discovered that by treating cotton fiber cellulose with camphor, a product that could be crafted into a variety of shapes became possible.

This original celluloid received immediate praise as the savior of elephants and tortoises. We felt like we could protect the natural world from the human's destructive need to consume. As new polymers went into the development process, the plastics advantages and disadvantages required constant review to avoid detrimental environmental impacts.

List of the Advantages of Plastics

1. Many plastics have a long lifespan that encourages reuse.
Plastics don't need to be a single-use product or be treated as disposable. Many forms of this material have a long lifespan that is equal to or greater than what other materials provided. A well-made and maintained PVC pipe has the capability of providing service for up to a century. Construction plastics have an average lifespan of 35 years. When we continue to use these items instead of throwing them away, then we can promote a lower waste rate instantly.

If you reuse plastic items at least seven times, then you're saving just as many energy resources than if you'd recycled the product.

2. Plastic production methods compare favorably to many other materials.
The plastics manufacturing process can be energy-intensive with fossil fuels, but it is still a resource that is more environmentally friendly than other materials. Bamboo provides natural fibers to use, although manufacturers must use chemical processes to turn the content into something useable. Aluminum is another example of a product that plastic beats with this advantage.

Recycling processes can change the comparison at times. It is still a clear advantage that plastics can provide when consistent reuse occurs. Even if you choose a fabric bag over a plastic one, you must use the reusable bag at least 40 times before you're matching the environmental footprint of a similar plastic product. Conventional cotton bags require 7,100 uses before creating a neutral investment.

3. Plastics take up less space in our landfills.
Even though it can take a significant amount of time for plastic materials to break down in a landfill, the amount of space that it takes up in these waste disposal areas is minimal when compared to other items. Paper products take up seven times more volume. When we can divert these items toward recycling programs or other uses, then we can start managing our landfill areas more effectively.

4. Methane doesn't form when plastics start decomposing.
Organic materials release greenhouse gases when they start decomposing. The focus of this process is often on carbon dioxide, but the methane that gets emitted is extremely problematic. When compared to CO2, methane is up to 20 times more potent as a reflecting atmospheric product.

Plastics don't emit this gas when it starts breaking down, which means it is easier to calculate the total lifecycle impact of the product.

5. It provides a safe way to transport our needed items.
One of the reasons why we use plastics for bottles that contain water and other beverages is because it keeps the product safe. We use the material to quickly and affordably get water to vulnerable populations all over the world. If a city experiences a shortage or emergency supplies are necessary after a natural disaster, we use this product to ensure that people can have their needs met.

Certain types of plastic were found to be potentially harmful with this advantage in the past, so legislative bans were put into place to prevent their use.

6. We have multiple ways to manage plastic waste.
Heat is one of the most common methods used to process plastic waste or create recycling opportunities. It isn't the only option that's available to use today. We can use pyrolysis or gasification to process this material with minimal emissions or pollution. It is even possible to shred the materials to create new fabrics from them.

Although the cost of the alternative processing methods isn't economically sustainable in some communities, this advantage is still present and worth considering. Some plastic bottles are even more eco-friendly than other materials when measured across several environmental indicators.

7. Plastics contain a high energy density to consider.
Incinerating plastics can be quite useful in some situations because of its high energy density rating. This material offers a significant energy output for cement kilns or incineration because we create it with the use of petroleum hydrocarbons. That means we can use it as a direct replacement for fossil fuel combustion since the foundation of the product comes from an energy resource that we all use.

The paper products sector in the United Kingdom uses almost the same amount of energy as the plastics and rubber industries. That's how useful this material can be from an energy standpoint.

8. Plastics are an affordable material.
We can keep costs down for a variety of items because of the low price point that's available for plastics. Our established manufacturing processes allow us to create several million tons of this material for a variety of purposes, ranging from packaging to straws. We can modify the chemistry of the material to provide specific beneficial properties for its end use, including the option to make it softer, harder, malleable, or durable.

9. The plastics industry is a significant contributor to the global economy.
The global plastic industry creates a market worth over $1 trillion annually. Almost two million people have direct employment opportunities in the United States because of this invention. We use it to prevent food waste, protect our health, and promote better hygiene. We have construction-grade and industrial plastics to use. It's essential for modern transportation, provides infrastructure support, and makes the delivery and transport of items cheaper and easier to complete.

Over 31,000 people in the United States are directly employed in the manufacturing of plastic bags. The plastics industry in the U.S. is currently the eighth-largest one presently operating.

List of the Disadvantages of Plastics

1. Plastics typically come from non-renewable resources.
Although the first plastic materials came from plant-based fibers, most of the items that we produce today have fossil fuels as their foundation. It's usually petroleum, but we can also use natural gas to develop this product. About 4% of these fuels goes directly into the plastics industry to create new products. When we look at the number of resources consumed during the refinement process and the expected rise in demand, the fossil fuel cost of plastics could reach 20% within the next decade.

2. The majority of the pollution found in the world's oceans is plastic.
Up to 80% of all marine debris contains plastic. This problem comes from land and marine sources, often collecting in large areas of open water where currents come together. This issue causes us to find waste on beaches, on land, and even in freshwater sources. Some of the items that get littered most often are plastic straws, stirrers, bottles, lids, and food wrappers.

Removing plastic pollution from ocean surface water comes at the cost of $5 per kilogram, but the item's reuse value is only $0.30. That's why the effort to clean up marine areas is being led by non-profit agencies.

3. Plastic pollution can lead to several economic losses.
Plastic packaging pollution by itself creates an economic loss of almost $80 billion to the global economy annually. It makes up nearly 50% of all waste from this industry, and virtually every other industry uses the item in some way. Building and construction plastics represent 16% of plastic use, while textiles are responsible for about 15%. Since it isn't profitable to recycle many of the items, more of it tends to go into waste streams instead of reuse.

The global average for plastic recycling is about 14%. India is one of the world's leaders by recycling approximately 60% of its items, while the United States comes in close to last in the developed world by recycling only 9%.

4. We cannot infinitely recycle plastic products.
Metals can be recycled numerous times into a variety of different products because of the properties of the material. Plastics don't share that opportunity. We can only reuse or recover it a specific number of times before it loses its quality and integrity. That means we are more likely to down-cycle this product, incinerate it, or stash it in a landfill.

Some plastic products and items can't be recycled at all, furthering the impact of this disadvantage. Over 93 billion plastic products don't get touched each year, which means they enter into our waste streams.

5. We must spend energy to clean plastics to recycle items.
Plastics that have cross-contamination with different types create unusable products. We also need to have the items cleaned before recyclers can turn the things into new pieces.

Some products contain different plastic types in the same item (i.e. a bottle and a lid), creating even more challenges to manage. It's a disadvantage that makes recycling inefficient at best for some communities - and sometimes impossible.

6. The re-sell chains for recycled plastic are long and challenging to manage.
Some recycling processing and re-sell chains for plastics tend to be long and inefficient. One item might change hands several times or travel a long distance to go through the recycling process. When it takes that much energy to reuse or recycle a product, then many of the potential benefits disappear. That's why some plastics have a high waste rate, especially if they aren't #1 or #2 options.

This disadvantage is one of the primary reasons why plastic is one of the most common materials found in municipal waste centers and landfills.

7. It takes a long time for plastic products to decompose.
Plastic takes a long time to degrade when compared to organic items. A plastic fishing line might take over 600 years to finally break down. Some researchers believe that some forms of this material might never fully decompose, remaining as nano plastics that could influence human, animal, and marine health in a variety of ways.

Even the plastic bags that we use to carry items every day can take 10 to 20 years to decompose naturally - but some of them can take up to an estimated 1,000 years. When you throw away a plastic water bottle, then it could take 450 years.

8. Plastics harm our ocean environments.
EcoWatch estimates that 10 metric tons of plastic products, including grocery bags, will wash out to the ocean from Los Angeles every day. Those items break down into small fragments that become microscopic in size and consumed by marine life. Up to 24,000 tons of plastic contaminate our food chain each year. Up to 25% of the fish sold in California markets contained fibrous or whole plastic in the animal's stomach. The chemicals from the plastic that leeches into these animals could possibly transfer to humans upon consumption.
Conclusion
Plastic is arguably the most revolutionary product in the history of humanity. It gives us a variety of ways to improve the safety of our foods and beverages while providing support mechanisms that create infrastructure benefits that we all use.

We have also discovered that endocrine disruptors are the link between plastic and human health hazards. PCBs and dioxins have already polluted the world's waterways. BPA, or bisphenol A, is specifically banned because of this trait - although people still receive exposure to it from a variety of sources. The CDC estimates that 95% of people have BPA contamination in their bodies.

When we look at these plastics advantages and disadvantages, it is imperative to remember that ingestion is not the only danger to consider. Simple exposures, the time it takes to decompose, and the litter we create are damaging our planet. We must increase our recycling rates and look for alternatives when it makes sense to decrease our exposure levels.

About the Author
Brandon Miller has a B.A. from the University of Texas at Austin. He is a seasoned writer who has written over one hundred articles, which have been read by over 500,000 people. If you have any comments or concerns about this blog post, then please contact the Green Garage team here.

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17 Biggest Advantages and Disadvantages of Plastics

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Plastics may be the most polarizing material of modern times. It provides a series of incredible benefits that help us every day, but the product can also be one of the most harmful substances on

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Please click here if you are not redirected within a few seconds.

Plastic packaging helps protect and preserve goods, while reducing weight in transportation, which saves fuel and reduces greenhouse gas emissions. From computers and cell phones to televisions and microwaves, durable, lightweight and affordable plastics have helped revolutionize the electronics we rely on every day.

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Please click here if you are not redirected within a few seconds. Plastic packaging helps protect and preserve goods, while reducing weight in transportation, which saves fuel and reduces greenhouse gas emissions. From computers and cell phones to televisions and microwaves, durable, lightweight and affordable plastics have helped revolutionize the electronics we rely on every day.

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A process called polymerisation is used to join single molecules (monomers) together to form a chain of many, the above example shows Vinyl Chloride bonded into Poly Vinyl Chloride. The left portion of the image shows the vinyl chloride while on the right hand side these single molecules of vinyl chloride have bonded together to form poly vinyl chloride, "poly" meaning many. Polymers are often formed from crude oil however more recently polymers have been created from corn starch and vegetable fats to form Bioplastics.

What is polymerisation?

Polymerisation is the chemical process of monomers joining together to form polymers, often it takes many thousands of monomers to make a single polymer. 2 types of polymerisation reactions are listed below.

1. Addition polymerisation- where monomers addon to each other with the addition of a catalyst, these are usually alkenes such as ethene and propene. Alkenes can act as monomers because they have a double bond.

2.Condensation Polymerisation - This is when monomers join or polymerise with a byproduct such as water, carbon dioxide or ammonia. This usually requires two different types of monomers that join alternately.

Polymers can have different structures and these can affect their properties, some examples are shown below.

Linear Chain

The chains when heated can flow easily this is a good example of the chain of a thermoplastic. Properties often associated with this type of chain are a weak material, ductile with a low density and melting point.

Branched Chain

Branched chains will not flow as easily when heated they will have a higher melting point than linear chains and typically have the properties of a slightly less ductile material (stronger and stiffer).

Cross Linked

The Cross linked bonding retains its shape when heated and is a good example of the bonding found in thermo set plastics. These also have a higher melting point than linear and branched bonds, they are usually a harder material but also more brittle.

The two main types of polymers are thermo sets and thermo plastics. Thermo plastics can be re-shaped after heating where as thermo sets cannot. Thermo plastics have the benefit of being recyclable and generally cheaper and easier to process than thermo set plastics.

Applications where polymers may be used.

Acrylic
Acrylic is a polymer called poly(methyl methacrylate) and is often used as an alternative to glass, examples of these include small fish tanks/aquariums visors in goggles and crash helmets covers for skylights and as it has good weatherproofing qualities it is commonly used for outdoor signage.

High Density Polythene (HDPE)
Babies baths, kitchen equipment, children's toys, fabric filaments.
Polythene is cheap and acid resisting. A strong polymer which softens at aroiund 120 degrees celcius.

Low Density Polythene (LDPE)
Used in plastic bags, film and packaging. LDPE is a more flexible polymer than HDPE. This softens at around 85 degrees celcius.

PVC (Poly Vinyl Chloride)
Industrial and domestic piping, artificial leather (e.g. shoes), protective clothing.
PVC is reasonably hard and hardwearing it is also fairly cheap

PEEK (Poly Ether Ketone)
Used in aggressive environments such as nuclear plants, oil and geo thermal wells, high pressure steam valves, aircraft and car engine parts.
Peek has a high melting point, very good tensile strength, has a low coefficient of friction and is light weight with good chemical resistance. It is however very costly.

Polymers and the environment

Polymers are difficult to dispose of as they can take many years to degrade. Many carrier and refuse bags now include substances such as corn starch to help them break down a little sooner.

A majority of polymers can be recycled but the process of doing so can be very costly as the different polymers need to separated from each other.

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Polymerisation- What is a polymer? What is polymerisation?

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A process called polymerisation is used to join single molecules (monomers) together to form a chain of many, the above example shows Vinyl Chloride bonded into Poly Vinyl Chloride. The left portion of the image shows the vinyl chloride while on the right hand side these single molecules of vinyl chloride have bonded together to form poly vinyl chloride, "poly" meaning many.

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Please click here if you are not redirected within a few seconds.

su·per·con·duc·tor

a substance capable of becoming superconducting at sufficiently low temperatures.

Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Wikipedia

What materials are superconductors

Aug 9, 2017 · These technologies are possible thanks to superconductors. Superconductors are materials ...Duration: 3:41 Posted: Aug 9, 2017

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Please click here if you are not redirected within a few seconds. A superconductor is a substance that conducts electricity without resistance when it becomes colder than a "critical temperature." At this temperature, electrons can move freely through the material. Superconductors are different from ordinary conductors, even very good ones.

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From your car to some of the electronics around your house, in nature to the laboratory, the modern world is filled with unbelievably impressive materials. Even more so, researchers are constantly looking for new materials that could be used to enhance some of the services and products we use every day, in laboratories or even in space.

When measuring the strength of a material it is a little more complicated than measuring just strength or hardness. You may think these two words are synonyms but for the seasoned material engineer, these words are nowhere near the same thing. The strength of a material indicates its resistance to deformation while the hardness of a material highlights how easily a material can be scratched.

Overall the strength of any material by its tensor strength or the resistive power of any material before breaking under continuous pressure. Tensile strengths have dimensions of force per unit area.

Do you know what the strongest material is on the planet? Well, today is your lucky day. The following list are some of the strongest materials on the planet

Human Bones

The first material is closer than you think. Though the bones in the body are not the strongest materials on this list they are still really durable.

There is probably a good chance that you have broken your bones at some point but your bones serve a lot of functions that include the production of white blood cells and store crucial minerals for your body.

Silicon Carbide

As stated in its name, silicon carbide is a semiconductor made of the materials carbon and silicon, occurring naturally in the mineral moissanite. Currently, the material is used across the automotive industry in electric appliances and in astronomy.

Cupronickel

Comprised of nickel, iron, manganese, and copper, cupronickel is a material that has a high resistance to corrosion and macrofouling, thermal conductivity, and strong tensile strength. The high corrosion resistance material is used a lot in the shipping industry to build hulls and the propellers of small fishing boats.

Titaniums Alloys

Source: National Museum of the United States Air Force

Titanium alloys are used across multiple industries including sports cars, commercial airplanes, missiles, and rockets. Industries and products like these need durable and lightweight materials to increase their performance.

Titanium alloys are very resistant to corrosion. However, due to the production costs, these materials are only used in high-end industries.

Spider Silk

Spider silk is one of the strongest naturally occurring materials on the Earth. As you probably already know, spiders use webs to catch prey and protect their offspring.

Though, the strength of spider silk varies from species to species, spider silk is almost as strong as premium quality steel and is half the strength of kevlar.

Glass Fiber

Glass fiber is similar to properties like polymers and carbon fiber. Created in 1932, glass fiber was used as thermal insulation for buildings. Nevertheless, the material is not as strong as carbon fiber, yet is much cheaper than the stronger material.

According to the Mohs scale, the diamond is the hardest known natural mineral found on the planet. Coming in a various amount of colors, diamonds are used in a wide range of industries including, manufacturing.

Diamonds themselves can only be scratched by other diamond. Some blue diamonds are natural semiconductors, electrical insulators, and are natural electrical conductors.

Kevlar was originally not used for tactical or military work. In the 1970s Kevlar was used as a replacement of steel in racing tires.

Across the globe, Kevlar is used for countless tools and products that include bicycle tires, racing sails, and the most commonly known, bulletproof vests. The high tensile strength to weight ratio makes it five times stronger than steel.

Patella Vulgata

Also known as a limpet, the patella vulgata is a species of sea snails found across Western Europe. The teeth the of aquatic creature can actually be stronger than spider silk which is officially the strongest naturally occurring material on Earth. The strength of patella vulgata of teeth is compared to that of carbon fibers.

Zylon

Developed by SRI International as an unique variety of thermoset liquid-crystalline polyoxazole, the created material is 1.6 times stronger than kevlar and shares the thermal stability of the material. You can find Zylon used in some sporting gear like Tennis racquets, table-tennis blades, and snowboards.

Carbon Fiber

The powerful and commonly used carbon fiber is an impressive feat of engineering. Carbon fiber strands are about 5-10 micrometers in diameter and composed mostly of carbon atoms.

The material is preferred over steel and other popular alloys because of high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance, and low thermal expansion. The material is used in aerospace, in the automotive industry, in sport, in civil engineering, and in the military.

Wurtzite Boron Nitrite

As one of the rarest materials in the world wurtzite boron nitrite is one of the strongest materials on this list. The material can be found naturally however because of its rarity wurtzite boron nitrite has to be synthesized. Wurtzite boron nitrite can withstand 18 percent more stress than a diamond.

Source: Wikipedia

Topping the list, graphene is the strongest materials known to humans. The transparent material is composed of a single layer carbon atom arranged in a triangular lattice and it's the basic structural element in charcoal, graphite and carbon nanotubes. Commonly used in the aerospace industry and automotive industries, graphene is 200 times than steel.

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Battle Royal: 13 of the World's Strongest Materials

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From your car to some of the electronics around your house, in nature to the laboratory, the modern world is filled with unbelievably impressive materials. Even more so, researchers are constantly looking for new materials that could be used to enhance some of the services and products we use every day, in laboratories or even in space.

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Densities of matter vary widely, from the density of interstellar gases (~10⁻²² assuming 90% H, 10% He; variable T) to that of an earth-mass black hole, whose theoretical mean density inside the Schwarzschild radius is about 4 × 10 ¹⁴ g/cm ³.

The Schwarzschild radius is the "point of no return" - once you get closer to the black hole than that, you can never escape. The theoretical density of a black hole depends on how big it is and how you define its size. The density at the center of a black hole is infinite (it's a famous "singularity"[1], which leads to difficulties in modern cosmology).

On Earth, densities range from 10⁻⁴ g/cm ³ for light gases to 0.001 g/cm ³ for aerogels and up to the heaviest substance, osmium, with a density of 22.61 g/cm ³. The terms heavy and light are commonly used in two different ways. We refer to weight when we say that an adult is heavier than a child. On the other hand, something else is alluded to when we say that styrofoam is heavier than an aerogel. A small sample of styrofoam would obviously weigh less than a roomful of aerogel, but styrofoam is heavier in the sense that a piece of given size weighs more than the same-size piece of balsa.

Material

ρ / g/cm³

Interstellar medium

10⁻²² − 10⁻¹²

Earth's atmosphere

0.0012

Aerogel

0.001 − 0.002

Styrofoam

0.030 − 0.120

Cork

0.220 − 0.260

Water

1.000

Plastics

0.850 − 1.400

Aluminum

2.7

The Earth (mean)

5.5153

Copper

8.920 − 8.960

Lead

11.340

osmium

22.61

The Inner Core

~13.000

Uranium

19.100

Iridium

22.500

The core of the Sun

~150.000

Atomic nuclei

~3 × 10 ¹⁴

Neutron star

8.4 × 10 ¹³ − 1 × 10 ¹⁵

Black hole

4 × 10 ¹⁴

Densities of many more materials are easily found.

What we are actually comparing is the mass per unit volume, that is, the density. In order to determine these densities, we might weigh a cubic centimeter of each material. If the styrofoam weighed 0.10 g and the aerogel 0.001 g, we could describe the density of styrofoam as 0.10 g cm ⁻³ and that of an aerogel as 0.001 g cm ⁻³. (Note that the negative exponent in the units cubic centimeters indicates a reciprocal. Thus 1 cm ⁻³ = 1/cm ³ and the units for our densities could be written as , g/cm ³, or g cm ⁻³. In each case the units are read as grams per cubic centimeter, the per indicating division.) We often abbreviate "cm ³" as "cc", and 1 cm ³ = 1 mL exactly, by definition.

In general it is not necessary to weigh exactly 1 cm ³ of a material in order to determine its density. We simply measure mass and volume and divide volume into mass:

\[\text{Density} = \dfrac{\text{mass}} {\text{volume}}\]

or

\[\rho = \dfrac{\text{m}} {\text{V}}\]

where ρ = density m = mass V = volume

Example \(\PageIndex{1}\): Density of a Black Hole

What is the density of a black hole?

A black hole contains about 3.7M (3.7 million) solar masses (a solar mass is 1.98892 × 10 ³³ grams) and is assumed to be a sphere with a Schwarzschild radius of 3x10 ⁵ cm x (M / M sun) where M is the mass of the black hole and M sun is the mass of the Sun. Typically, M for a black hole in our galaxy is around 10 times the mass of the Sun, but for supermassive black holes at the centers of galaxies it can be millions or even billions [3]. What is its density?
Solution
You can use the Schwarzschild radius to calculate the "density" of the black hole - i.e., the mass divided by the volume enclosed within the Schwarzschild radius.

The radius of the sphere must be calculated first, using the formula 3x10 ⁵ cm x (M / M sun) we get 3x10 ⁵ cm x 3.7 × 10 ⁶ = 1.125 × 10 ¹²

\[\text{V} = \frac{4}{3} \pi \text{r}^3 = \frac{4}{3} \times \text{3.142} \times (\text{1.125} \times \text{10}^{12} \text{cm})^3 = \text{5.964} \times \text{10} ^{36} \text{cm}^3 \nonumber\]

The mass of the sphere is 3.7 x 10 ⁶ M sun × 1.98892 × 10 ³³ g/M sun = 7.359 × 10 ³⁹ g

\[ \begin{align*} \text{Density} =\rho &= \frac{\text{m}} {\text{V}} \\[4pt] &= \dfrac{\text{7.359} \times \text{10}^{39}}{\text{5.964} \times \text{10}^{36}} = \text{1.31} \times \text{10}^3 \frac{\text{g}}{\text{cc}} \end{align*}\]

You might have recognized a shortcut: the density is

\[(\text{1.8} \times \text{10}^{16} \frac{\text{g}}{\text{cm}^3}) \times (\frac{\text{M}_{sun}}{\text{M}})^2 \nonumber\]

or

\[\text{1.8} \times \text{10}^{16}\frac{\text{g}}{\text{cm}^3} \times (\dfrac{1}{\text{3.7} \times \text{10}^6})^2 = \text{1.31} \times \text{10}^3 \frac{\text{g}}{\text{cc}} \nonumber\]

From the point of view of an outside observer, this might as well be the actual black hole density, since the distribution of matter within the Schwarzschild radius has no effect on the outside.

Example \(\PageIndex{2}\): Black Hole and an Atom

There is a rough analogy between a black hole and an atom. In both cases, the mass is concentrated in a tiny region at the center, but the "size" of the object is much bigger. The radius of a nucleus is (r = A 1/3 x 1.7 x 10⁻¹³ cm), where A is the mass number of the nucleus. The radius of the whole atom is on the order of 100-200 pm (10⁻⁸ cm, 10 ⁵ times as large, so all the mass of an atom resides in ~10⁻¹²% of its volume).

1. What is the volume of an aluminum-27 nucleus?

2. What is the mass of an aluminum nucleus in grams, if each particle has a mass of ~1 amu (1.6 x 10⁻²⁷ g) and the mass deficit is ignored?

3. What is the density of the Al nucleus, in g/cm³

Solution

1. \(\text{r} = (\text{27})^{\frac{1}{3}} \times \text{1.7} \times \text{10}^{-13} \text{cm} = \text{5.1} \times \text{10}^{-13} \text{cm V} = \frac{4}{3} \pi \text{r}^3 = \text{5.56} \times \text{10}^{-37} \text{cm}^3\)

2. \(\text{m} = \text{27} \times \text{1.6} \times \text{10}^{-24} \text{g} = \text{4.32} \times \text{10}^{-23} \text{g}\)

3. \(\text{D} = \frac{\text{m}}{\text{V}} = \dfrac{\text{4.32} \times \text{10}^{-23} \text{g}}{\text{5.56} \times \text{10}^{-37} \text{cm}^3} = \text{7.77} \times \text{10}^{13} \frac{\text{g}}{\text{cm}^3}\)

Example \(\PageIndex{3}\): Density Calculation

Calculate the density of

1. a piece of aluminum whose mass is 37.42 g and which, when submerged, increases the water level in a graduated cylinder by 13.9 ml

2. an aluminum cylinder of mass 25.07 g, radius 0.750 cm, and height 5.25 cm.

Solution
a) Since the submerged metal displaces its own volume,

\[\text{Density} =\rho = \frac{\text{m}} {\text{V}} = \frac{37.42 g} {13.9 mL} = \text {2.69 g/mL or 2.69 g mL}^{-1}\]

b) The volume of the cylinder must be calculated first, using the formula

\[\text{V} = {\pi} r^{2} h = 3.142 × \text{(0.750 cm)}^{2} * 5.25 \text{cm} = \text{9.278 718 8 cm}^{3}\]

Then

\[\begin{align*} \rho = \frac{\text{m}} {\text{V}} = \frac{25.07g} {9.278 718 8cm^{3}} \\[4pt] &= \text{2.70} \frac{\text{g}}{\text{cm}^3} \end{align*}\]

Note that unlike mass or volume, the density of a substance is independent of the size of the sample. Thus density is a property by which one substance can be distinguished from another. A sample of pure aluminum can be trimmed to any desired volume or adjusted to have any mass we choose, but its density will always be 2.70 g/cm ³ at 20°C. The densities of some common pure substances are listed in the Table.

Tables and graphs are designed to provide a maximum of information in a minimum of space. When a physical quantity (number × units) is involved, it is wasteful to keep repeating the same units. Therefore it is conventional to use pure numbers in a table or along the axes of a graph. A pure number can be obtained from a quantity if we divide by appropriate units. For example, when divided by the units gram per cubic centimeter, the density of aluminum becomes a pure number 2.70:

\[\frac{\text{Density of aluminum}} {\text{1 g cm}^{-3}} = \frac{\text{2.70 g cm}^{-3}} {\text{1 g cm}^{-3}} = 2.70\]

Therefore, a column in a table or the axis of a graph is conveniently labeled in the following form:

\[\frac{\text{Quantity}}{\text{units}}\]

This indicates the units that must be divided into the quantity to yield the pure number in the table or on the axis. This has been done in the second column of the Table.

Converting Densities

In our exploration of Density, notice that chemists may express densities differently depending on the subject. The density of pure substances may be expressed in kg/m ³ in some journals which insist on strict compliance with SI units; densities of soils may be expressed in lb/ft ³ in some agricultural or geological tables; the density of a cell may be expressed in mg/µL; and other units are in common use. It is easy to transform densities from one set of units to another, by multiplying the original quantity by one or more unity factors:

1. lb/cm³ and

2. lb/ft³

Solution
or

Contributors and Attributions

# data[].attributes.attachment_link.description
Densities of matter vary widely, from the density of interstellar gases (~10-22 assuming 90% H, 10% He; variable T) to that of an earth-mass black hole, whose theoretical mean density inside the Schwarzschild radius is about 4 × 10 14 g/cm 3.

# data[].attributes.attachment_link.readable_text
The elements of the periodic table sorted by melting point

click on any element's name for further chemical properties, environmental data or health effects.

This list contains the 118 elements of chemistry.

The chemical elements of
the periodic chart sorted by: Melting-
point Name chemical element Symbol Atomic number

For chemistry students and teachers: The tabular chart on the right is arranged by melting point.

The chemical element with the lowest melting point is Helium and the element with the highest melting point is Carbon.

The unity used for the melting point is Celsius (C). Click here: to convert Celsius to Fahrenheit or Kelvin.

Please note that the elements do not show their natural relation towards each other as in the Periodic system. There you can find the metals, semi-conductor(s), non-metal(s), inert noble gas(ses), Halogens, Lanthanoides, Actinoids (rare earth elements) and transition metals.

30
Gallium Ga
31

816.8
Arsenic As
33

Darmstadtium Ds
110

Click here: for a schematic overview of the periodic table of elements in chart form Please report any accidental mistake in the above statistics on chemical elements

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health and environmental effects melting point element elements periodic table chart measurement laboratory environment healthy

# data[].attributes.attachment_link.title
The chemical elements of the periodic table sorted by melting point

# data[].attributes.attachment_link.description
click on any element's name for further chemical properties, environmental data or health effects. This list contains the 118 elements of chemistry. The chemical elements of the periodic chart sorted by: Melting- point Name chemical element Symbol Atomic number For chemistry students and teachers: The tabular chart on the right is arranged by melting point.

# data[].attributes.attachment_link.readable_text
Densities of matter vary widely, from the density of interstellar gases (~10⁻²² assuming 90% H, 10% He; variable T) to that of an earth-mass black hole, whose theoretical mean density inside the Schwarzschild radius is about 4 × 10 ¹⁴ g/cm ³.

The Schwarzschild radius is the "point of no return" - once you get closer to the black hole than that, you can never escape. The theoretical density of a black hole depends on how big it is and how you define its size. The density at the center of a black hole is infinite (it's a famous "singularity"[1], which leads to difficulties in modern cosmology).

On Earth, densities range from 10⁻⁴ g/cm ³ for light gases to 0.001 g/cm ³ for aerogels and up to the heaviest substance, osmium, with a density of 22.61 g/cm ³. The terms heavy and light are commonly used in two different ways. We refer to weight when we say that an adult is heavier than a child. On the other hand, something else is alluded to when we say that styrofoam is heavier than an aerogel. A small sample of styrofoam would obviously weigh less than a roomful of aerogel, but styrofoam is heavier in the sense that a piece of given size weighs more than the same-size piece of balsa.

Material

ρ / g/cm³

Interstellar medium

10⁻²² − 10⁻¹²

Earth's atmosphere

0.0012

Aerogel

0.001 − 0.002

Styrofoam

0.030 − 0.120

Cork

0.220 − 0.260

Water

1.000

Plastics

0.850 − 1.400

Aluminum

2.7

The Earth (mean)

5.5153

Copper

8.920 − 8.960

Lead

11.340

osmium

22.61

The Inner Core

~13.000

Uranium

19.100

Iridium

22.500

The core of the Sun

~150.000

Atomic nuclei

~3 × 10 ¹⁴

Neutron star

8.4 × 10 ¹³ − 1 × 10 ¹⁵

Black hole

4 × 10 ¹⁴

Densities of many more materials are easily found.

What we are actually comparing is the mass per unit volume, that is, the density. In order to determine these densities, we might weigh a cubic centimeter of each material. If the styrofoam weighed 0.10 g and the aerogel 0.001 g, we could describe the density of styrofoam as 0.10 g cm ⁻³ and that of an aerogel as 0.001 g cm ⁻³. (Note that the negative exponent in the units cubic centimeters indicates a reciprocal. Thus 1 cm ⁻³ = 1/cm ³ and the units for our densities could be written as , g/cm ³, or g cm ⁻³. In each case the units are read as grams per cubic centimeter, the per indicating division.) We often abbreviate "cm ³" as "cc", and 1 cm ³ = 1 mL exactly, by definition.

In general it is not necessary to weigh exactly 1 cm ³ of a material in order to determine its density. We simply measure mass and volume and divide volume into mass:

\[\text{Density} = \dfrac{\text{mass}} {\text{volume}}\]

or

\[\rho = \dfrac{\text{m}} {\text{V}}\]

where ρ = density m = mass V = volume

Example \(\PageIndex{1}\): Density of a Black Hole

What is the density of a black hole?

A black hole contains about 3.7M (3.7 million) solar masses (a solar mass is 1.98892 × 10 ³³ grams) and is assumed to be a sphere with a Schwarzschild radius of 3x10 ⁵ cm x (M / M sun) where M is the mass of the black hole and M sun is the mass of the Sun. Typically, M for a black hole in our galaxy is around 10 times the mass of the Sun, but for supermassive black holes at the centers of galaxies it can be millions or even billions [3]. What is its density?
Solution
You can use the Schwarzschild radius to calculate the "density" of the black hole - i.e., the mass divided by the volume enclosed within the Schwarzschild radius.

The radius of the sphere must be calculated first, using the formula 3x10 ⁵ cm x (M / M sun) we get 3x10 ⁵ cm x 3.7 × 10 ⁶ = 1.125 × 10 ¹²

\[\text{V} = \frac{4}{3} \pi \text{r}^3 = \frac{4}{3} \times \text{3.142} \times (\text{1.125} \times \text{10}^{12} \text{cm})^3 = \text{5.964} \times \text{10} ^{36} \text{cm}^3 \nonumber\]

The mass of the sphere is 3.7 x 10 ⁶ M sun × 1.98892 × 10 ³³ g/M sun = 7.359 × 10 ³⁹ g

\[ \begin{align*} \text{Density} =\rho &= \frac{\text{m}} {\text{V}} \\[4pt] &= \dfrac{\text{7.359} \times \text{10}^{39}}{\text{5.964} \times \text{10}^{36}} = \text{1.31} \times \text{10}^3 \frac{\text{g}}{\text{cc}} \end{align*}\]

You might have recognized a shortcut: the density is

\[(\text{1.8} \times \text{10}^{16} \frac{\text{g}}{\text{cm}^3}) \times (\frac{\text{M}_{sun}}{\text{M}})^2 \nonumber\]

or

\[\text{1.8} \times \text{10}^{16}\frac{\text{g}}{\text{cm}^3} \times (\dfrac{1}{\text{3.7} \times \text{10}^6})^2 = \text{1.31} \times \text{10}^3 \frac{\text{g}}{\text{cc}} \nonumber\]

From the point of view of an outside observer, this might as well be the actual black hole density, since the distribution of matter within the Schwarzschild radius has no effect on the outside.

Example \(\PageIndex{2}\): Black Hole and an Atom

There is a rough analogy between a black hole and an atom. In both cases, the mass is concentrated in a tiny region at the center, but the "size" of the object is much bigger. The radius of a nucleus is (r = A 1/3 x 1.7 x 10⁻¹³ cm), where A is the mass number of the nucleus. The radius of the whole atom is on the order of 100-200 pm (10⁻⁸ cm, 10 ⁵ times as large, so all the mass of an atom resides in ~10⁻¹²% of its volume).

1. What is the volume of an aluminum-27 nucleus?

2. What is the mass of an aluminum nucleus in grams, if each particle has a mass of ~1 amu (1.6 x 10⁻²⁷ g) and the mass deficit is ignored?

3. What is the density of the Al nucleus, in g/cm³

Solution

1. \(\text{r} = (\text{27})^{\frac{1}{3}} \times \text{1.7} \times \text{10}^{-13} \text{cm} = \text{5.1} \times \text{10}^{-13} \text{cm V} = \frac{4}{3} \pi \text{r}^3 = \text{5.56} \times \text{10}^{-37} \text{cm}^3\)

2. \(\text{m} = \text{27} \times \text{1.6} \times \text{10}^{-24} \text{g} = \text{4.32} \times \text{10}^{-23} \text{g}\)

3. \(\text{D} = \frac{\text{m}}{\text{V}} = \dfrac{\text{4.32} \times \text{10}^{-23} \text{g}}{\text{5.56} \times \text{10}^{-37} \text{cm}^3} = \text{7.77} \times \text{10}^{13} \frac{\text{g}}{\text{cm}^3}\)

Example \(\PageIndex{3}\): Density Calculation

Calculate the density of

1. a piece of aluminum whose mass is 37.42 g and which, when submerged, increases the water level in a graduated cylinder by 13.9 ml

2. an aluminum cylinder of mass 25.07 g, radius 0.750 cm, and height 5.25 cm.

Solution
a) Since the submerged metal displaces its own volume,

\[\text{Density} =\rho = \frac{\text{m}} {\text{V}} = \frac{37.42 g} {13.9 mL} = \text {2.69 g/mL or 2.69 g mL}^{-1}\]

b) The volume of the cylinder must be calculated first, using the formula

\[\text{V} = {\pi} r^{2} h = 3.142 × \text{(0.750 cm)}^{2} * 5.25 \text{cm} = \text{9.278 718 8 cm}^{3}\]

Then

\[\begin{align*} \rho = \frac{\text{m}} {\text{V}} = \frac{25.07g} {9.278 718 8cm^{3}} \\[4pt] &= \text{2.70} \frac{\text{g}}{\text{cm}^3} \end{align*}\]

Note that unlike mass or volume, the density of a substance is independent of the size of the sample. Thus density is a property by which one substance can be distinguished from another. A sample of pure aluminum can be trimmed to any desired volume or adjusted to have any mass we choose, but its density will always be 2.70 g/cm ³ at 20°C. The densities of some common pure substances are listed in the Table.

Tables and graphs are designed to provide a maximum of information in a minimum of space. When a physical quantity (number × units) is involved, it is wasteful to keep repeating the same units. Therefore it is conventional to use pure numbers in a table or along the axes of a graph. A pure number can be obtained from a quantity if we divide by appropriate units. For example, when divided by the units gram per cubic centimeter, the density of aluminum becomes a pure number 2.70:

\[\frac{\text{Density of aluminum}} {\text{1 g cm}^{-3}} = \frac{\text{2.70 g cm}^{-3}} {\text{1 g cm}^{-3}} = 2.70\]

Therefore, a column in a table or the axis of a graph is conveniently labeled in the following form:

\[\frac{\text{Quantity}}{\text{units}}\]

This indicates the units that must be divided into the quantity to yield the pure number in the table or on the axis. This has been done in the second column of the Table.

Converting Densities

In our exploration of Density, notice that chemists may express densities differently depending on the subject. The density of pure substances may be expressed in kg/m ³ in some journals which insist on strict compliance with SI units; densities of soils may be expressed in lb/ft ³ in some agricultural or geological tables; the density of a cell may be expressed in mg/µL; and other units are in common use. It is easy to transform densities from one set of units to another, by multiplying the original quantity by one or more unity factors:

1. lb/cm³ and

2. lb/ft³

Solution
or

Contributors and Attributions

# data[].attributes.attachment_link.description
Densities of matter vary widely, from the density of interstellar gases (~10-22 assuming 90% H, 10% He; variable T) to that of an earth-mass black hole, whose theoretical mean density inside the Schwarzschild radius is about 4 × 10 14 g/cm 3.

# data[].attributes.attachment_link.readable_text
Stiffness is the extent to which an object resists deformation in response to an applied force.

The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is.

The stiffness, k, of a body is a measure of the resistance offered by an elastic body to deformation. For an elastic body with a single degree of freedom (DOF) (for example, stretching or compression of a rod), the stiffness is defined as

where,

F is the force on the body

is the displacement produced by the force along the same degree of freedom (for instance, the change in length of a stretched spring)

In the International System of Units, stiffness is typically measured in newtons per meter ( ). In Imperial units, stiffness is typically measured in pounds(lbs) per inch.

Generally speaking, deflections (or motions) of an infinitesimal element (which is viewed as a point) in an elastic body can occur along multiple DOF (maximum of six DOF at a point). For example, a point on a horizontal beam can undergo both a vertical displacement and a rotation relative to its undeformed axis. When there are M degrees of freedom a M x M matrix must be used to describe the stiffness at the point. The diagonal terms in the matrix are the direct-related stiffnesses (or simply stiffnesses) along the same degree of freedom and the off-diagonal terms are the coupling stiffnesses between two different degrees of freedom (either at the same or different points) or the same degree of freedom at two different points. In industry, the term influence coefficient is sometimes used to refer to the coupling stiffness.

It is noted that for a body with multiple DOF, the equation above generally does not apply since the applied force generates not only the deflection along its own direction (or degree of freedom) but also those along with other directions.

For a body with multiple DOF, in order to calculate a particular direct-related stiffness (the diagonal terms), the corresponding DOF is left free while the remaining should be constrained. Under such a condition, the above equation can be used to obtain the direct-related stiffness for the degree of freedom which is unconstrained. The ratios between the reaction forces (or moments) and the produced deflection are the coupling stiffnesses.

A description including all possible stretch and shear parameters is given by the elasticity tensor.

The inverse of stiffness is flexibility or compliance, typically measured in units of metres per newton. In rheology, it may be defined as the ratio of strain to stress, and so take the units of reciprocal stress, e.g. 1/ Pa.

A body may also have a rotational stiffness, k, given by

where

In the SI system, rotational stiffness is typically measured in newton-metres per radian.

In the SAE system, rotational stiffness is typically measured in inch- pounds per degree.

Further measures of stiffness are derived on a similar basis, including:

shear stiffness - the ratio of applied shear force to shear deformation

torsional stiffness - ratio of applied torsion moment to angle of twist

The elastic modulus of a material is not the same as the stiffness of a component made from that material. Elastic modulus is a property of the constituent material; stiffness is a property of a structure or component of a structure, and hence it is dependent upon various physical dimensions that describe that component. That is, the modulus is an intensive property of the material; stiffness, on the other hand, is an extensive property of the solid body that is dependent on the material and its shape and boundary conditions. For example, for an element in tension or compression, the axial stiffness is

where

Similarly, the torsional stiffness of a straight section is

where

Note that the torsional stiffness has dimensions [force] * [length] / [angle], so that its SI units are N*m/rad.

For the special case of unconstrained uniaxial tension or compression, Young's modulus can be thought of as a measure of the stiffness of a structure.

The stiffness of a structure is of principal importance in many engineering applications, so the modulus of elasticity is often one of the primary properties considered when selecting a material. A high modulus of elasticity is sought when deflection is undesirable, while a low modulus of elasticity is required when flexibility is needed.

In biology, the stiffness of the extracellular matrix is important for guiding the migration of cells in a phenomenon called durotaxis.

Another application of stiffness finds itself in skin biology. The skin maintains its structure due to its intrinsic tension, contributed to by collagen, an extracellular protein which accounts for approximately 75% of its dry weight. The pliability of skin is a parameter of interest that represents its firmness and extensibility, encompassing characteristics such as elasticity, stiffness, and adherence. These factors are of functional significance to patients.[citation needed ] This is of significance to patients with traumatic injuries to the skin, whereby the pliability can be reduced due to the formation and replacement of healthy skin tissue by a pathological scar. This can be evaluated both subjectively, or objectively using a device such as the Cutometer. The Cutometer applies a vacuum to the skin and measures the extent to which it can be vertically distended. These measurements are able to distinguish between healthy skin, normal scarring, and pathological scarring, and the method has been applied within clinical and industrial settings to monitor both pathophysiological sequelae, and the effects of treatments on skin.

# data[].attributes.attachment_link.description
Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. The stiffness, k, of a body is a measure of the resistance offered by an elastic body to deformation.

# data[].attributes.attachment_link.readable_text
"Pear Cut," "Marquise Cut," "Princess Cut" (Zales)-the progression of cleaving, cutting, and shaping a diamond has been developed and refined with improved technologies since the first polishing of a diamond's facets during the Middle Ages. Before that time, diamonds were used only in their natural octahedral state due to difficulty in cutting. So why are diamonds so hard to cut?

The difficulty in cutting a diamond comes from its molecular composition and structure. A diamond is a pure, or nearly pure, extremely hard form of carbon that has naturally crystallized in the isometric system. Carbon atoms are stacked in a rigid three-dimensional framework and formed under high pressure and intense heat. This results in an extremely hard substance, a ten on the Mohs scale of mineral hardness.

The hardness of the diamond prevents arbitrary cleaving; instead, the shape of a diamond cut is related to the natural shape of the rough stone. Diamonds naturally occur in a range of forms, from nearly faultless crystals to dark, nodular lumps. Each of these forms is valuable, either as gems or as grinding and cutting grit.

Using these imperfect stones as cutting grit belies the main theory: only a diamond can truly cut another diamond. Diamonds are cut with specialized tools that make use of diamond tipped phosphor bronze or diamond dusted steel blades. Such tools are used to exploit the structural weakness of the diamond by grooving and striking along specific tetrahedral planes. Diamond dust-charged cast iron disks revolve around the rough cut, polishing facets and creating its brilliant, symmetrical shape.

The cut of a diamond has the greatest influence on the diamond's perceived beauty, as the angle of its facets directly relates to its ability to refract light, known as "light performance," or brilliance. Thus, each jewelry company has developed high-tech equipment for analyzing its compounds, facet angles, and index of brilliance to attract consumers. Slogans such as Zales' "Four C's-color, clarity, cut, carat" begin to enlighten the consumer, lending a scientific analysis to this modern symbol of love.

# data[].attributes.attachment_link.description
"Pear Cut," "Marquise Cut," "Princess Cut" (Zales)-the pro­gression of cleaving, cutting, and shaping a diamond has been developed and refined with improved technologies since the first polishing of a diamond's facets during the Middle Ages. Before that time, diamonds were used only in their natural octahedral state due to difficulty in cutting.

# data[].attributes.headline
HardnessThe hardness of a material is how difficult it is to cut into.Solids can be hard because their particles are held togetherby very strong bonds. The hardest material found in nature isdiamond. Diamond can cut most materials and this explains why many industrial drills have diamond tips.

# data[].attributes.subject
HardnessThe hardness of a material is how difficult it is to cut into.Solids can be hard because their particles are held togetherby very strong bonds. The hardest material found in nature isdiamond. Diamond can cut most materials and this explains why many industrial drills have diamond tips.

# data[].attributes.body
Conductivity
Corrosion Resistance
Density
Ductility / Malleability
Elasticity / Stiffness
Fracture Toughness
Hardness
Plasticity
Strength, Fatigue
Strength, Shear
Strength, Tensile
Strength, Yield
Toughness
Wear Resistance

# data[].attributes.attachment_link.readable_text
Spider silk is a protein fibre spun by spiders. Spiders use their silk to make webs or other structures, which function as sticky nets to catch other animals, or as nests or cocoons to protect their offspring, or to wrap up prey. They can also use their silk to suspend themselves, to float through the air, or to glide away from predators. Most spiders vary the thickness and stickiness of their silk for different uses.

In some cases, spiders may even use silk as a source of food. While methods have been developed to collect silk from a spider by force, it is difficult to gather silk from many spiders compared to silk-spinning organisms such as silkworms.

All spiders produce silk, and even in non-web building spiders, silk is intimately tied to courtship and mating. Silk produced by females provides a transmission channel for male vibratory courtship signals, while webs and draglines provide a substrate for female sex pheromones. Observations of male spiders producing silk during sexual interactions are also common across phylogenetically widespread taxa. However, the function of male-produced silk in mating has received very little study.

All spiders produce silks, and a single spider can produce up to seven different types of silk for different uses. This is in contrast to insect silks, where an individual usually only produces one type of silk. Spider silks may be used in many different ecological ways, each with properties to match the silk's function. As spiders have evolved, so has their silks' complexity and diverse uses, for example from primitive tube webs 300-400 million years ago to complex orb webs 110 million years ago.

Prey capture

The orb webs produced by the Araneidae (typical orb-weavers); tube webs; tangle webs; sheet webs; lace webs, dome webs; single thread used by the Bolas spiders for "fishing".

Prey immobilisation

Silk used as "swathing bands" to wrap up prey. Often combined with immobilising prey using a venom. In species of Scytodes the silk is combined with venom and squirted from the chelicerae.

Reproduction

Male spiders may produce sperm webs; spider eggs are covered in silk cocoons.

Dispersal

"Ballooning" or "kiting" used by smaller spiders to float through the air, for instance for dispersal.

Source of food

The kleptoparasitic eating the silk of host spider webs. Some daily weavers of temporary webs also eat their own unused silk daily, thus mitigating a heavy metabolic expense.

Nest lining and nest construction

Tube webs used by "primitive" spiders such as the European tube web spider (Segestria florentina). Threads radiate out of nest to provide a sensory link to the outside. Silk is a component of the lids of spiders that use "trapdoors", such as members of the family Ctenizidae, and the "water" or "diving bell" spider Argyroneta aquatica builds its diving bell of silk.

Guide lines

Some spiders that venture from shelter will leave a trail of silk by which to find their way home again.

Drop lines and anchor lines

Many spiders, such as the Salticidae, that venture from shelter and leave a trail of silk, use that as an emergency line in case of falling from inverted or vertical surfaces. Many others, even web dwellers, will deliberately drop from a web when alarmed, using a silken thread as a drop line by which they can return in due course. Some, such as species of Paramystaria, also will hang from a drop line when feeding.

Alarm lines

Some spiders that do not spin actual trap webs do lay out alarm webs that the feet of their prey (such as ants) can disturb, cueing the spider to rush out and secure the meal if it is small enough, or to avoid contact if the intruder seems too formidable.

Pheromonal trails

Some wandering spiders will leave a largely continuous trail of silk impregnated with pheromones that the opposite sex can follow to find a mate.

Meeting the specification for all these ecological uses requires different types of silk suited to different broad properties, as either a fibre, a structure of fibres, or a silk-globule. These types include glues and fibres. Some types of fibres are used for structural support, others for constructing protective structures. Some can absorb energy effectively, whereas others transmit vibration efficiently. In a spider, these silk types are produced in different glands; so the silk from a particular gland can be linked to its use by the spider.

Ampullate (major)

Dragline silk - used for the web's outer rim and spokes, also for the lifeline and for ballooning.

Ampullate (minor)

Used for temporary scaffolding during web construction.

Flagelliform

Capture-spiral silk - used for the capturing lines of the web.

Tubuliform

Egg cocoon silk - used for protective egg sacs.

Aciniform

Used to wrap and secure freshly captured prey; used in the male sperm webs; used in stabilimenta.

Aggregate

A silk glue of sticky globules.

Piriform

Used to form bonds between separate threads for attachment points.

Each spider and each type of silk has a set of mechanical properties optimised for their biological function.

Most silks, in particular dragline silk, have exceptional mechanical properties. They exhibit a unique combination of high tensile strength and extensibility ( ductility). This enables a silk fibre to absorb a large amount of energy before breaking ( toughness, the area under a stress-strain curve).

A frequent mistake made in the mainstream media is to confuse strength and toughness, when comparing silk to other materials.[citation needed ] Weight for weight, silk is stronger than steel, but not as strong as Kevlar. Silk is, however, tougher than both.

The variability of mechanical properties of spider silk fibres may be important and it is related to their degree of molecular alignment. Mechanical properties depend strongly on the ambient conditions, i.e. humidity and temperature.

A dragline silk's tensile strength is comparable to that of high-grade alloy steel (450−2000 MPa), and about half as strong as aramid filaments, such as Twaron or Kevlar (3000 MPa).

Consisting of mainly protein, silks are about a sixth of the density of steel (1.3 g/cm ³). As a result, a strand long enough to circle the Earth would weigh less than 500 grams (18 oz). (Spider dragline silk has a tensile strength of roughly 1.3 GPa. The tensile strength listed for steel might be slightly higher-e.g. 1.65 GPa, but spider silk is a much less dense material, so that a given weight of spider silk is five times as strong as the same weight of steel.)

Energy density

Silks are also extremely ductile, with some able to stretch up to five times their relaxed length without breaking.

The combination of strength and ductility gives dragline silks a very high toughness (or work to fracture), which "equals that of commercial polyaramid ( aromatic nylon) filaments, which themselves are benchmarks of modern polymer fibre technology".

While unlikely to be relevant in nature, dragline silks can hold their strength below −40 °C (−40 °F) and up to 220 °C (428 °F). As occurs in many materials, spider silk fibres undergo a glass transition. The glass-transition temperature depends on the humidity, as water is a plasticiser for the silk.

When exposed to water, dragline silks undergo supercontraction, shrinking up to 50% in length and behaving like a weak rubber under tension. Many hypotheses have been suggested as to its use in nature, with the most popular being to automatically tension webs built in the night using the morning dew.[citation needed ]

The toughest known spider silk is produced by the species Darwin's bark spider ( Caerostris darwini): "The toughness of forcibly silked fibers averages 350 , with some samples reaching 520 MJ/m ³. Thus, C. darwini silk is more than twice as tough as any previously described silk, and over 10 times tougher than Kevlar".

Silk fibre is a two-compound pyriform secretion, spun into patterns (called "attachment discs") that are employed to adhere silk threads to various surfaces using a minimum of silk substrate. The pyriform threads polymerise under ambient conditions, become functional immediately, and are usable indefinitely, remaining biodegradable, versatile and compatible with numerous other materials in the environment. The adhesive and durability properties of the attachment disc are controlled by functions within the spinnerets. Some adhesive properties of the silk resemble glue, consisting of microfibrils and lipid enclosures.

Many species of spiders have different glands to produce silk with different properties for different purposes, including housing, web construction, defence, capturing and detaining prey, egg protection, and mobility (fine "gossamer" thread for ballooning, or for a strand allowing the spider to drop down as silk is extruded). Different specialised silks have evolved with properties suitable for different uses. For example, Argiope argentata has five different types of silk, each used for a different purpose:

major-ampullate (dragline) silk

Used for the web's outer rim and spokes and also for the lifeline. Can be as strong per unit weight as steel, but much tougher.

capture-spiral (flagelliform) silk

Used for the capturing lines of the web. Sticky, extremely stretchy and tough. The capture spiral is sticky due to droplets of aggregate (a spider glue) that is placed on the spiral. The elasticity of flagelliform allows for enough time for the aggregate to adhere to the aerial prey flying into the web.

tubiliform (a.k.a. cylindriform) silk

Used for protective egg sacs. Stiffest silk.

aciniform silk

Used to wrap and secure freshly captured prey. Two to three times as tough as the other silks, including dragline.

minor-ampullate silk

Used for temporary scaffolding during web construction.

Piriform (pyriform)

Piriform serves as the attachment disk to dragline silk. Piriform is used in attaching spider silks together to construct a stable web.

Silks, like many other biomaterials, have a hierarchical structure. The primary structure is the amino acid sequence of its proteins ( spidroin), mainly consisting of highly repetitive glycine and alanine blocks, which is why silks are often referred to as a block co-polymer. On a secondary structure level, the short side chained alanine is mainly found in the crystalline domains ( beta sheets) of the nanofibril, glycine is mostly found in the so-called amorphous matrix consisting of helical and beta turn structures. It is the interplay between the hard crystalline segments, and the strained elastic semi-amorphous regions, that gives spider silk its extraordinary properties. Various compounds other than protein are used to enhance the fibre's properties. Pyrrolidine has hygroscopic properties which keeps the silk moist while also warding off ant invasion. It occurs in especially high concentration in glue threads. Potassium hydrogen phosphate releases hydrogen ions in aqueous solution, resulting in a pH of about 4, making the silk acidic and thus protecting it from fungi and bacteria that would otherwise digest the protein. Potassium nitrate is believed to prevent the protein from denaturing in the acidic milieu.

This first very basic model of silk was introduced by Termonia in 1994 who suggested crystallites embedded in an amorphous matrix interlinked with hydrogen bonds. This model has refined over the years: semi-crystalline regions were found as well as a fibrillar skin core model suggested for spider silk, later visualised by AFM and TEM. Sizes of the nanofibrillar structure and the crystalline and semi-crystalline regions were revealed by neutron scattering.

It has been possible to relate microstructural information and macroscopic mechanical properties of the fibres. The results show that ordered regions (i) mainly reorient by deformation for low-stretched fibres and (ii) the fraction of ordered regions increases progressively for higher stretching of the fibres.

Schematic of the spider's orb web, structural modules, and spider silk structure.[37] On the left is shown a schematic drawing of an orb web. The red lines represent the dragline, radial line, and frame lines, the blue lines represent the spiral line, and the centre of the orb web is called the "hub". Sticky balls drawn in blue are made at equal intervals on the spiral line with viscous material secreted from the aggregate gland. Attachment cement secreted from the piriform gland is used to connect and fix different lines. Microscopically, the spider silk secondary structure is formed of spidroin and is said to have the structure shown on the right side. In the dragline and radial line, a crystalline β-sheet and an amorphous helical structure are interwoven. The large amount of β-spiral structure gives elastic properties to the capture part of the orb web. In the structural modules diagram, a microscopic structure of dragline and radial lines is shown, composed mainly of two proteins of MaSp1 and MaSp2, as shown in the upper central part. In the spiral line, there is no crystalline β-sheet region.

Various compounds other than protein are found in spider silks, such as sugars, lipids, ions, and pigments that might affect the aggregation behaviour and act as a protection layer in the final fibre.

The production of silks, including spider silk, differs in an important aspect from the production of most other fibrous biological materials: rather than being continuously grown as keratin in hair, cellulose in the cell walls of plants, or even the fibres formed from the compacted faecal matter of beetles; it is "spun" on demand from liquid silk precursor out of specialised glands.

The spinning process occurs when a fibre is pulled away from the body of a spider, whether by the spider's legs, by the spider's falling under its own weight, or by any other method including being pulled by humans. The term "spinning" is misleading because no rotation of any component occurs, but rather comes from analogy to the textile spinning wheels. Silk production is a pultrusion, similar to extrusion, with the subtlety that the force is induced by pulling at the finished fibre rather than being squeezed out of a reservoir. The unspun silk fibre is pulled through silk glands of which there may be both numerous duplicates and different types of gland on any one spider species.

The gland's visible, or external, part is termed the spinneret. Depending on the complexity of the species, spiders will have two to eight spinnerets, usually in pairs. There exist highly different specialised glands in different spiders, ranging from simply a sac with an opening at one end, to the complex, multiple-section major ampullate glands of the golden silk orb-weavers.

Behind each spinneret visible on the surface of the spider lies a gland, a generalised form of which is shown in the figure to the right, "Schematic of a generalised gland".

Gland characteristics

1. The first section of the gland labelled 1 on Figure 1 is the secretory or tail section of the gland. The walls of this section are lined with cells that secrete proteins Spidroin I and Spidroin II, the main components of this spider's dragline. These proteins are found in the form of droplets that gradually elongate to form long channels along the length of the final fibre, hypothesised to assist in preventing crack formation or even self-healing of the fibre.

2. The second section is the storage sac. This stores and maintains the gel-like unspun silk dope until it is required by the spider. In addition to storing the unspun silk gel, it secretes proteins that coat the surface of the final fibre.

3. The funnel rapidly reduces the large diameter of the storage sac to the small diameter of the tapering duct.

4. The final length is the tapering duct, the site of most of the fibre formation. This consists of a tapering tube with several tight about turns, a valve almost at the end (mentioned in detail at point No. 5 below) ending in a spigot from which the solid silk fibre emerges. The tube here tapers hyperbolically, therefore the unspun silk is under constant elongational shear stress, which is an important factor in fibre formation. This section of the duct is lined with cells that exchange ions, reduce the dope pH from neutral to acidic, and remove water from the fibre. Collectively, the shear stress and the ion and pH changes induce the liquid silk dope to undergo a phase transition and condense into a solid protein fibre with high molecular organisation. The spigot at the end has lips that clamp around the fibre, controlling fibre diameter and further retaining water.

5. Almost at the end of the tapering duct is a valve, approximate position marked "5" on figure 1. Though discovered some time ago, the precise purpose of this valve is still under discussion. It is believed to assist in restarting and rejoining broken fibres, acting much in the way of a helical pump, regulating the thickness of the fibre, and/or clamping the fibre as a spider falls upon it. There is some discussion of the similarity of the silk worm's silk press and the roles each of these valves play in the production of silk in these two organisms.

Throughout the process the unspun silk appears to have a nematic texture, in a similar manner to a liquid crystal, arising in part due to the extremely high protein concentration of silk dope (around 30% in terms of weight per volume). This allows the unspun silk to flow through the duct as a liquid but maintain a molecular order.

As an example of a complex spinning field, the spinneret apparatus of an adult Araneus diadematus (garden cross spider) consists of the glands shown below. Similar multiple gland architecture exists in the black widow spider.

500 pyriform glands for attachment points

4 ampullate glands for the web frame

about 300 aciniform glands for the outer lining of egg sacs, and for ensnaring prey

4 tubuliform glands for egg sac silk

4 aggregate glands for adhesive functions

2 coronate glands for the thread of adhesion lines

To artificially synthesise spider silk into fibres, there are two broad areas that must be covered. These are synthesis of the feedstock (the unspun silk dope in spiders), and synthesis of the spinning conditions (the funnel, valve, tapering duct, and spigot). There have been a number of different approaches but few of these methods have produced silk that can efficiently be synthesised into fibres.

The molecular structure of unspun silk is both complex and extremely long. Though this endows the silk fibres with their desirable properties, it also makes replication of the fibre somewhat of a challenge. Various organisms have been used as a basis for attempts to replicate some components or all of some or all of the proteins involved. These proteins must then be extracted, purified and then spun before their properties can be tested.

Organism

Details

Average Maximum breaking stress (MPa)

Average Strain (%)

Reference

Darwin's bark spider ( Caerostris darwini)

Malagasy spider famed for making webs with strands up to 25 m long, across rivers. " C. darwini silk is more than twice as tough as any previously described silk"

1850 ±350

33 ±0.08

E. coli

Synthesising a large and repetitive molecule (~300 kDa) is complex, but required for the strongest silk. Here E. coli was engineered to produce a 556 kDa protein. Fibers spun from these synthetic spidroins are the first to fully replicate the mechanical performance of natural spider silk by all common metrics.

1030 ±110

18 ±6

Goats

Goats were genetically modified to secrete silk proteins in their milk, which could then be purified.

285-250

30-40

Tobacco & potato plants

Tobacco and potato plants were genetically modified to produce silk proteins. Patents were granted, but no fibres have yet been described in the literature.

n/a

n/a

Spider silks with comparatively simple molecular structure need complex ducts to be able to spin an effective fibre. There have been a number of methods used to produce fibres, of which the main types are briefly discussed below.

Feedstock is simply forced through a hollow needle using a syringe. This method has been shown to make fibres successfully on multiple occasions.

Although very cheap and easy to produce, the shape and conditions of the gland are very loosely approximated. Fibres created using this method may need encouragement to change from liquid to solid by removing the water from the fibre with such chemicals as the environmentally undesirable methanol or acetone, and also may require post-stretching of the fibre to attain fibres with desirable properties.

As the field of microfluidics matures, it is likely that more attempts to spin fibres will be made using microfluidics. These have the advantage of being very controllable and able to test spin very small volumes of unspun fibre but setup and development costs are likely to be high. A patent has been granted in this area for spinning fibres in a method mimicking the process found in nature, and fibres are successfully being continuously spun by a commercial company.

Electrospinning is a very old technique whereby a fluid is held in a container in a manner such that it is able to flow out through capillary action. A conducting substrate is positioned below, and a large difference in electrical potential is applied between the fluid and the substrate. The fluid is attracted to the substrate, and tiny fibres jump almost instantly from their point of emission, the Taylor cone, to the substrate, drying as they travel. This method has been shown to create nano-scale fibres from both silk dissected from organisms and regenerated silk fibroin.

Silk can be formed into other shapes and sizes such as spherical capsules for drug delivery, cell scaffolds and wound healing, textiles, cosmetics, coatings, and many others. Spider silk proteins can also self-assemble on superhydrophobic surfaces to generate nanowires, as well as micron-sized circular sheets. It has recently been shown that recombinant spider silk proteins can self-assemble at the liquid air interface of a standing solution to form protein permeable, super strong, and super flexible membranes that support cell proliferation. Suggested applications include skin transplants, and supportive membranes in organ-on-a-chip.

Due to spider silk being a scientific research field with a long and rich history, there can be unfortunate occurrences of researchers independently rediscovering previously published findings. What follows is a table of the discoveries made in each of the constituent areas, acknowledged by the scientific community as being relevant and significant by using the metric of scientific acceptance, citations. Thus, only papers with 50 or more citations are included.

Area of contribution

Year

Main researchers [Ref]

Title of paper

Contribution to the field

1960

"The Composition of Arthropod Silk Fibrons; Comparative studies of fibroins"

Reconstituted /Synthetic Spider Silk and Artificial Spinning

1995

Prince, J. T., Kaplan, D. L. & et al.

"Construction, Cloning, and Expression of Synthetic Genes Encoding Spider Dragline Silk"

First successful synthesis of Spider silk by E. coli.

Peasants in the southern Carpathian Mountains used to cut up tubes built by and cover wounds with the inner lining. It reportedly facilitated healing, and even connected with the skin. This is believed to be due to antiseptic properties of spider silk and because the silk is rich in vitamin K, which can be effective in clotting blood.[verify ] Due to the difficulties in extracting and processing substantial amounts of spider silk, the largest known piece of cloth made of spider silk is an 11-by-4-foot (3.4 by 1.2 m) textile with a golden tint made in Madagascar in 2009. Eighty-two people worked for four years to collect over one million golden orb spiders and extract silk from them.

The silk of Nephila clavipes was used in research concerning mammalian neuronal regeneration.

Spider silk has been used as a thread for crosshairs in optical instruments such as telescopes, microscopes, and telescopic rifle sights. In 2011, spider silk fibres were used in the field of optics to generate very fine diffraction patterns over N-slit interferometric signals used in optical communications. In 2012, spider silk fibres were used to create a set of violin strings.

Development of methods to mass-produce spider silk has led to manufacturing of military, medical and consumer goods, such as ballistics armour, athletic footwear, personal care products, breast implant and catheter coatings, mechanical insulin pumps, fashion clothing, and outerwear.

Spider silk is used to suspend inertial confinement fusion targets during laser ignition, as it remains considerably elastic and has a high energy to break at temperatures as low as 10-20 K. In addition, it is made from "light" atomic number elements that won't emit x-rays during irradiation that could preheat the target so that the pressure differential required for fusion is not achieved.

Spider silk has been used to create biolenses that could be used in conjunction with lasers to create high-resolution images of the inside of the human body.[1]

Replicating the complex conditions required to produce fibres that are comparable to spider silk has proven difficult in research and early-stage manufacturing. Through genetic engineering, Escherichia coli bacteria, yeasts, plants, silkworms, and animals have been used to produce spider silk proteins, which have different, simpler characteristics than those from a spider. Extrusion of protein fibres in an aqueous environment is known as "wet-spinning". This process has so far produced silk fibres of diameters ranging from 10 to 60 μm, compared to diameters of 2.5-4 μm for natural spider silk. Artificial spider silks have fewer and simpler proteins than natural dragline silk, and are consequently half the diameter, strength, and flexibility of natural dragline silk.

In March 2010, researchers from the Korea Advanced Institute of Science & Technology succeeded in making spider silk directly using the bacteria E. coli, modified with certain genes of the spider Nephila clavipes. This approach eliminates the need to milk spiders and allows the manufacture of the spider silk in a more cost-effective manner.

A 556 kDa spider silk protein was manufactured from 192 repeat motifs of the Nephila clavipes dragline spidroin, having similar mechanical characteristics as their natural counterparts, i.e., tensile strength (1.03 ± 0.11 GPa), modulus (13.7 ± 3.0 GPa), extensibility (18 ± 6%), and toughness (114 ± 51 MJ/m3).

The company AMSilk developed spidroin using bacteria, making it into an artificial spider silk.

The company Bolt Threads produces a recombinant spidroin using yeast, for use in apparel fibers and personal care. They produced the first commercial apparel products made of recombinant spider silk, trademarked Microsilk™, demonstrated in ties and beanies. They have also partnered with vegan activist and luxury designer Stella McCartney as well as Adidas to produce Microsilk™ garments.

The company Kraig Biocraft Laboratories used research from the Universities of Wyoming and Notre Dame to create silkworms that were genetically altered to produce spider silk.

The now defunct Canadian biotechnology company Nexia successfully produced spider silk protein in transgenic goats that carried the gene for it; the milk produced by the goats contained significant quantities of the protein, 1-2 grams of silk proteins per litre of milk. Attempts to spin the protein into a fibre similar to natural spider silk resulted in fibres with tenacities of 2-3 grams per denier. Nexia used wet spinning and squeezed the silk protein solution through small extrusion holes in order to simulate the behavior of the spinneret, but this procedure was not sufficient to replicate the stronger properties of native spider silk.

The company Spiber has produced a synthetic spider silk that they are calling Q/QMONOS. In partnership with Goldwin, a ski parka made from this synthetic spider silk is currently in testing and is to be in mass production soon for less than $120,000 YEN.

1. Miyashita, Tadashi; Maezono, Yasunori; Shimazaki, Aya (2004). "Silk feeding as an alternative foraging tactic in a kleptoparasitic spider under seasonally changing environments" (PDF). Journal of Zoology. 262 (3): 225-229. CiteSeerX 10.1.1.536.9091. doi:10.1017/S0952836903004540.

2. ^ Hillyard, P. (2007). The Private Life of Spiders. London: New Holland. p. 160. ISBN 978-1-84537-690-1.

3. ^ Nentwig, W. & Heimer, S. (1987). Wolfgang Nentwig (ed.). Ecological aspects of spider webs. Springer-Verlag. p. 211.

4. ^ Flying spiders over Texas! Coast to Coast. Chad B., Texas State University Undergrad Archived 26 November 2011 at the Wayback Machine Describes the mechanical kiting of Spider "ballooning".

5. ^ Holm, Erik, Dippenaar-Schoeman, Ansie; Goggo Guide; LAPA publishers (URL: WWW.LAPA.co.za). 2010[page needed ]

6. ^ Griffiths, J. R.; Salanitri, V. R. (1980). "The strength of spider silk". Journal of Materials Science. 15 (2): 491-496. Bibcode:1980JMatS..15..491G. doi:10.1007/BF00551703. S2CID 135628690.

7. ^ Ganio Mego, Paolo (c. 2002). "Material Tensile Strength Comparison". Archived from the original on 26 October 2009.

8. ^ Blackledge, TA; Hayashi, CY (2006). "Silken toolkits: Biomechanics of silk fibers spun by the orb web spider Argiope argentata (Fabricius 1775)". The Journal of Experimental Biology. 209 (Pt 13): 2452-2461. doi:10.1242/jeb.02275. PMID 16788028.

9. Heimer, S. (1988). Wunderbare Welt der Spinnen. Urania. p. 12

10. ^ Plaza, G.R.; Pérez-Rigueiro, J.; Riekel, C.; Perea, G.B.; Agulló-Rueda, F.; Burghammer, M.; Guinea, G.V.; Elices, M. (2012). "Relationship between microstructure and mechanical properties in spider silk fibers: identification of two regimes in the microstructural changes". Soft Matter. 8 (22): 6015-6026. Bibcode:2012SMat....8.6015P. doi:10.1039/C2SM25446H.

11. ^ Zhao, Yue; Hien, Khuat Thi Thu; Mizutani, Goro; Rutt, Harvey N. (June 2017). "Second-order nonlinear optical microscopy of spider silk". Applied Physics B. 123 (6): 188. arXiv:. Bibcode:2017ApPhB.123..188Z. doi:10.1007/s00340-017-6766-z. S2CID 51684427.

12. ^ Zhao, Yue; Li, Yanrong; Hien, K. T. T.; Mizutani, Goro; Rutt, Harvey N. (2019). "Observation of Spider Silk by Femtosecond Pulse Laser Second Harmonic Generation Microscopy". Surf. Interface Anal. 51 (1): 50-56. arXiv:. doi:10.1002/sia.6545. S2CID 104921418.

13. ^ Eisoldt, L.; Thamm, C.; Scheibel, T. (2012). "The role of terminal domains during storage and assembly of spider silk proteins". Biopolymers. 97 (6): 355-361. doi:10.1002/bip.22006. PMID 22057429. S2CID 46685716.

14. ^ Knight, D. P.; Vollrath, F. (1999). "Liquid crystals and flow elongation in a spider's silk production line". Proc. R. Soc. B. 266 (1418): 519-523. doi:10.1098/rspb.1999.0667. PMC .

15. ^ Wilson, R. S. (1962). "The Control of Dragline Spinning in the Garden Spider". Quarterly Journal of Microscopical Science. 103: 557-571.

16. ^ Magoshi, J.; Magoshi, Y. & Nakamura, S. (1985). "Physical properties and structure of silk: 9. Liquid crystal formation of silk fibroin". Polym. Commun. 26: 60-61.

17. ^ Chen, Xin; Knight, David P.; Vollrath, Fritz (1 July 2002). "Rheological characterization of nephila spidroin solution". Biomacromolecules. 3 (4): 644-648. doi:10.1021/bm0156126. ISSN 1525-7797. PMID 12099805.

18. ^ Jeffery, F; La Mattina, C; Tuton-Blasingame, T; Hsia, Y; Gnesa, E; Zhao, L; Franz, A; Vierra, C (2011). "Microdissection of Black Widow Spider Silk-producing Glands". Journal of Visualized Experiments (47): 2382. doi:10.3791/2382. PMC . PMID 21248709.

19. ^ Swanson, B. O.; Blackledge, T. A.; Summers, A. P. & Hayashi, C. Y. (2006). "Spider dragline silk: Correlated and mosaic evolution in high-performance biological materials" (PDF). Evolution. 60 (12): 2539-2551. doi:10.1554/06-267.1. PMID 17263115. S2CID 14862626.

20. ^ US patent 2008109923, Lewis, R. V., "Expression of spider silk proteins", published 2010-05-25, assigned to University of Wyoming

21. ^ Lucas, F.; Shaw, J. T. B. & Smith, S. G. (1960). "The Composition of Arthropod Silk Fibrons". Insect Chemistry. Symp. 3: 208-214.

22. ^ Knight, D. P. & Vollrath, F. (1999). "Liquid crystals and flow elongation in a spider's silk production line". Proceedings of the Royal Society B. 266 (1418): 519-523. doi:10.1098/rspb.1999.0667. PMC .

23. ^ Leggett, Hadley (23 September 2009). "1 Million Spiders Make Golden Silk for Rare Cloth". Wired.

24. Berenbaum, May R., ^ Field Notes - Spin Control, The Sciences, The New York Academy Of Sciences, September/October 1995

25. ^ Example of use of spider silk for telescopic rifle sights. Bonnier Corporation. 1955.

26. ^ Duarte F. J.; Taylor, T S; Black, A M; Davenport, W E; Varmette, P G (2011). "N-slit interferometer for secure free-space optical communications: 527 m intra interferometric path length". Journal of Optics. 13 (3): 5710. Bibcode:2011JOpt...13c5710D. doi:10.1088/2040-8978/13/3/035710.

27. ^ Osaki, Shigeyoshi (2012). "Spider Silk Violin Strings with a Unique Packing Structure Generate a Soft and Profound Timbre". Physical Review Letters. 108 (15): 154301. Bibcode:2012PhRvL.108o4301O. doi:10.1103/PhysRevLett.108.154301. PMID 22587257.

28. ^ "University of Notre Dame and Kraig Biocraft Laboratories Create Artificial Spider Silk Breakthrough" (Press release). Kraig Biocraft Laboratories. 29 September 2010.

29. ^ "Fraser Research Publicly Announced at Press Conference" (Press release). University of Notre Dame. 1 October 2010. Archived from the original on 10 October 2010.

# data[].attributes.attachment_link.description
Spider silk is a protein fibre spun by spiders. Spiders use their silk to make webs or other structures, which function as sticky nets to catch other animals, or as nests or cocoons to protect their offspring, or to wrap up prey.

# data[].attributes.attachment_link.readable_text
There is a difference between the mechanical and physical properties of an alloy.

Physical properties are things that are measurable. Those are things like density, melting point, conductivity, coefficient of expansion, etc.

Mechanical properties are how the metal performs when different forces are applied to them. That includes things like strength, ductility, wear resistance, etc.

The mechanical and physical properties of materials are determined by their chemical composition and their internal structure, like grain size or crystal structure. Mechanical properties may be greatly affected by processing due to the rearrangement of the internal structure. Metalworking processes or heat treatment might play a role in affecting some physical properties like density and electrical conductivity, but those effects are usually insignificant.

Mechanical and physical properties are a key determinant for which alloy is considered suitable for a given application when multiple alloys satisfy the service conditions. In almost every instance, the engineer designs the part to perform within a given range of properties. Many of the mechanical properties are interdependent - high performance in one category may be coupled with lower performance in another. Higher-strength, as an example, maybe achieved at the expense of lower ductility. So a broad understanding of the product's environment will lead to the selection of the best material for the application.

A description of some common mechanical and physical properties will provide information that product designers could consider in selecting materials for a given application.

1. Conductivity

2. Corrosion Resistance

3. Density

4. Ductility / Malleability

5. Elasticity / Stiffness

6. Fracture Toughness

7. Hardness

8. Plasticity

9. Strength, Fatigue

10. Strength, Shear

11. Strength, Tensile

12. Strength, Yield

13. Toughness

14. Wear Resistance

Expanding on those definitions:

1. Conductivity

Thermal conductivity is a measure of the quantity of heat that flows through a material. It is measured as one degree per unit of time, per unit of cross-sectioned area, per unit of length. Materials with low thermal conductivity may be used as insulators, those with high thermal conductivity may be a heat sink. Metals that exhibit high thermal conductivity would be candidates for use in applications like heat exchangers or refrigeration. Low thermal conductivity materials may be used in high temperature applications, but often high temperature components require high thermal conductivity, so it is important to understand the environment. Electrical conductivity is similar, measuring the quantity of electricity that is transferred through a material of known cross-section and length.

2. Corrosion resistance

Corrosion resistance describes a material's ability to prevent natural chemical or electro-chemical attack by atmosphere, moisture or other agents. Corrosion takes many forms including pitting, galvanic reaction, stress corrosion, parting, inter-granular, and others (many of which will be discussed in other newsletter editions). Corrosion resistance may be expressed as the maximum depth in mils to which corrosion would penetrate in one year; it is based on a linear extrapolation of penetration occurring during the lifetime of a given test or service. Some materials are intrinsically corrosion resistant, while others benefit from the addition of plating or coatings. Many metals that belong to families that resist corrosion are not totally safe from it, and are still subject to the specific environmental conditions where they operate.

3. Density

Density, often expressed as pounds per cubic inch, or grams per cubic centimeter, etc., describes the mass of the alloy per unit volume. The density of the alloy will determine how much a component of a certain size will weigh. This factor is important in applications like aerospace or automotive where weight is important. Engineers looking for lower weight components may seek alloys that are less dense, but must then consider the strength to weight ratio. A higher density material like steel might be chosen, for example, if it provides higher strength than a lower density material. Such a part could be made thinner so that less material could help compensate for the higher density.

4. Ductility / Malleability

Ductility is the ability of a material to deform plastically (that is, stretch) without fracturing and retain the new shape when the load is removed. Think of it as the ability to stretch a given metal into a wire. Ductility is often measured using a tensile test as a percentage of elongation, or the reduction in the cross sectional area of the sample before failure. A tensile test can also be used to determine the Young's Modulus or modulus of elasticity, an important stress/strain ratio used in many design calculations. The tendency of a material to resist cracking or breaking under stress makes ductile materials appropriate for other metalworking processes including rolling or drawing. Certain other processes like cold-working tend to make a metal less ductile.

Malleability, a physical property, describes a metal's ability to be formed without breaking. Pressure, or compressive stress, is used to press or roll the material into thinner sheets. A material with high malleability will be able to withstand higher pressure without breaking.

5. Elasticity, Stiffness

Elasticity describes a material's tendency to return to its original size and shape when a distorting force is removed. As opposed to materials that exhibit plasticity (where the change in shape is not reversible), an elastic material will return to its previous configuration when the stress is removed.

The stiffness of a metal is often measured by the Young's Modulus, which compares the relationship between stress (the force applied) and strain (the resulting deformation). The higher the Modulus - meaning greater stress results in proportionally lesser deformation - the stiffer the material. Glass would be an example of a stiff/high Modulus material, where rubber would be a material that exhibits low stiffness/low Modulus. This is an important design consideration for applications where stiffness is required under load.

6. Fracture Toughness

Impact resistance is a measure of a material's ability to withstand a shock. The effect of impact - a collision that occurs in a short period of time - is typically greater than the effect of a weaker force delivered over a longer period. So a consideration of impact resistance should be included when the application includes an elevated risk of impact. Certain metals may perform acceptably under static load but fail under dynamic loads or when subjected to a collision. In the lab, impact is often measured through a common Charpy test, where a weighted pendulum strikes a sample opposite of machined V-notch.

7. Hardness

Hardness is defined as a material's ability to resist permanent indentation (that is plastic deformation). Typically, the harder the material, the better it resists wear or deformation. The term hardness, thus, also refers to local surface stiffness of a material or its resistance to scratching, abrasion, or cutting. Hardness is measured by employing such methods as Brinell, Rockwell, and Vickers, which measure the depth and area of a depression by a harder material, including a steel ball, diamond, or other indenter.

8. Plasticity

Plasticity, the converse of elasticity, describes the tendency of a certain solid material to hold its new shape when subjected to forming forces. It is the quality that allows materials to be bent or worked into a permanent new shape. Materials transition from elastic behavior to plastic at the yield point.

9. Strength - Fatigue

Fatigue can lead to fracture under repeated or fluctuating stresses (for example loading or unloading) that have a maximum value less than the tensile strength of the material. Higher stresses will accelerate the time to failure, and vice versa, so there is a relationship between the stress and cycles to failure. Fatigue limit, then, refers to the maximum stress the metal can withstand (the variable) in a given number of cycles. Conversely, the fatigue life measure holds the load fixed and measures how many load cycles the material can withstand before failure. Fatigue strength is an important consideration when designing components subjected to repetitive load conditions.

10. Strength - Shear

Shear strength is a consideration in applications like bolts or beams where the direction as well as the magnitude of the stress is important. Shear occurs when directional forces cause the internal structure of the metal to slide against itself, at the granular level.

11. Strength - Tensile

One of the most common metal property measures is Tensile, or Ultimate, Strength. Tensile strength refers to the amount of load a section of metal can withstand before it breaks. In lab testing, the metal will elongate but return to its original shape through the area of elastic deformation. When it reaches the point of permanent or plastic deformation (measured as Yield), it retains the elongated shape even when load is removed. At the Tensile point, the load causes the metal to ultimately fracture. This measure helps differentiate between materials that are brittle from those that are more ductile. Tensile or ultimate tensile strength is measured in Newtons per square millimeter (Mega Pascals or MPa) or pounds per square inch.

12. Strength - Yield

Similar in concept and measure to Tensile Strength, Yield Strength describes the point after which the material under load will no longer return to its original position or shape. Deformation moves from elastic to plastic. Design calculations include the Yield Point to understand the limits of dimensional integrity under load. Like Tensile strength, Yield strength is measured in Newtons per square millimeter (Mega Pascals or MPa) or pounds per square inch.

13. Toughness

Measured using the Charpy impact test similar to Impact Resistance, toughness represents a material's ability to absorb impact without fracturing at a given temperature. Since impact resistance is often lower at low temperatures, materials may become more brittle. Charpy values are commonly prescribed in ferrous alloys where the possibilities of low temperatures exist in the application (e.g. offshore oil platforms, oil pipelines, etc.) or where instantaneous loading is a consideration (e.g. ballistic containment in military or aircraft applications).

14. Wear resistance

Wear resistance is a measure of a material's ability to withstand the effect of two materials rubbing against each other. This can take many forms including adhesion, abrasion, scratching, gouging, galling, and others. When the materials are of different hardness, the softer metal can begin to show the effects first, and management of that may be part of the design. Even rolling can cause abrasion because of the presence of foreign materials. Wear resistance may be measured as the amount of mass lost for a given number of abrasion cycles at a given load.

Considering this information about mechanical and physical properties can promote an optimized metal selection for a given application. Because of the multitude of materials available - and the ability to modify properties through alloying and often through heat treatment efforts - it can be time well spent to consult with metallurgical experts to select the material that provides the needed performance balanced with cost-effectiveness.

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How To Evaluate Materials - Properties To Consider | MetalTek

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Physical properties are things that are measurable. Those are things like density, melting point, conductivity, coefficient of expansion, etc. Mechanical properties are how the metal performs when different forces are applied to them. That includes things like strength, ductility, wear resistance, etc.