A364 Lesson 6 by NURALYSHA ERIENA BINTE AZHAR https://padlet.com/21014969_2/kd99o1zxmdbs03wv en-us 2022-11-22 05:56:26 UTC 2026-01-23 17:05:06 UTC hello@padlet.com Lesson 6 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393648920 2022-11-22 06:01:15 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393648920 flow properties https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393649730 2022-11-22 06:02:01 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393649730 instrument 21014969_2 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393651106 rotational viscometer
- measures fluid viscosity at fixed rotation speed
- uses a spindle in test fluid
- usually gives viscosity at a single shear rate
- measures dynamic viscosity

rheometers
- automatically measure viscosity over specified shear rate or time range
- measures viscosity values in continuous run
- provides a rheology profile in an experiment]]> 2022-11-22 06:03:32 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393651106 newtonian fluid https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393652280 -ideally viscous flow behaviour
-viscocity is not dependant on shear/applied rate

relationship between shear stress and shear rate: straight line

]]> 2022-11-22 06:04:50 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393652280 newtonian liquid https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393671919 viscocity vs shear rate graph: constant viscocity as shear rate increases, constant viscocity with time]]> 2022-11-22 06:25:46 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393671919 non newtonian fluid https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393672854 2022-11-22 06:26:49 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393672854 shear thinning(pseudoplastic flow) https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393674060 shear stress to shear rate graph: increases non linearly. ]]> 2022-11-22 06:28:04 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393674060 shear thinning(pseudoplastic) https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393678207 viscocity decreases as shear rate increases. 
for example, more strength used to mix yoghurt, the less viscous the yoghurt becomes ]]> 2022-11-22 06:32:23 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393678207 shear thickening(dilatant) https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393694479 shear stress to shear rate graph is increasing non linearly]]> 2022-11-22 06:49:43 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393694479 shear thickening(dilatant) https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393697042 viscosity increases as shear rate increases.
for example, more strength used to stir corn starch results in corn starch being more viscous ]]> 2022-11-22 06:52:35 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393697042 non newtonian fluid: thixotropic and rheopectic https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393699205 these are fluids that have flow behaviour based on time(time dependant)

thixotropic fluid: Viscosity decreases with time at constant shear rate
rheopectic fluid: Viscosity increases with time at constant shear rate]]> 2022-11-22 06:54:54 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393699205 Amplitude Sweep 21001804_3 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393766560 deflection of the measuring system is increased step-wise from one measuring point to the next while keeping frequency at a constant value.

Test determines:
Linear viscoelastic region
Structural strength
Rigidity (stiffness)
Structural stability
Dynamic yield point and flow point (for viscoelastic solids)

]]> 2022-11-22 07:57:05 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393766560 Linear Viscoelastic Region (LVE) 21001804_3 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393775241 Indicates range in which test can be carried out without destroying the structure of the sample 

Shows plateau (constant) value ]]> 2022-11-22 08:04:34 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393775241 21001804_3 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393777292 •G' > G'‘ - a gel-like / solid structure -  viscoelastic solid material.
•G'' > G' - a fluid structure - viscoelastic liquid. 
]]> 2022-11-22 08:06:35 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393777292 Yield Point and Flow Point 21001804_3 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393781661 Ty (yield point/ stress yield): 
 - Shear stress limit of the LVE region. 
 - “to yield” means to give way or to soften
 - This point is also called the linearity limit.

Tf (flow point/flow stress): 
- The shear stress value at the crossover point G' = G''. 
- At higher shear, the viscous portion will dominate à the sample flows
]]> 2022-11-22 08:10:54 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2393781661 Frequency Sweeps 21027391_2 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394041864 Frequency sweep...
- constant amplitude
- constant temperature
- varying frequency

Test determines...
- molecular weight
- molecular weight distribution
- degree of crosslinking
- stability
- impact resistance]]> 2022-11-22 12:05:01 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394041864 21027391_2 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394047143 Uncrossedlinked polymer
Low frequency, G">G'
Crossover point G' = G" = the value of angular frequency
If crossover occurs at lower frequency, material has higher molar mass
Crosslinked polymer
G' > G"
G' value at lower frequency can be used to compare the crosslinking density of different samples
Higher G' value, stiffer the material, higher degree of crosslinking]]> 2022-11-22 12:09:54 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394047143 crosslinking in polymer 21027391_2 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394047790 2022-11-22 12:10:32 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394047790 Frequency sweep of dispersion 21027391_2 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394054201 Long term storage behaviour of dispersion in lower frequency range
If G'>G", solid structure is caused by stable network of forces
If G">G', material is liquid and susceptible to segregation

]]> 2022-11-22 12:16:07 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394054201 Oscillatory test 210332111 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394114716 Measure store and energy loss without destroying the object itself. (viscoelastic properties)]]> 2022-11-22 13:05:41 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394114716 Shear Modulus,G 210332111 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394131668 G=Shear stress/ shear strain.

Shear stress can be found using: shear force(F)/surface area(A)

Shear strain can be found: deflection path(s)/shear gap(h)

The higher the G value, the stiffer the material. This means that a larger force is required to produce deformation.

]]> 2022-11-22 13:16:49 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394131668 G' & G'' and the graph 210332111 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394151727 G': storage module (solid-like: spring). The capacity of the object able to store energy
G'': Loss modulus (viscous-like). The part that energy are being lost to heat due to friction

If the angle of g prime is more than 45 degree(closer to G''): then the material will behave more like liquid. Higher loss modulus than storage modulus

If the angle of g prime is less than 45 degree (closer to G'): the material will behave more like solid. Higher storage modules than loss modulus

If the g complex lies at 45 degree, then it behaves half like solid and half liquid at the same time (posses both properties)]]> 2022-11-22 13:30:31 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394151727 object relating to G' & G'' 210332111 https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394156745 This tells us that most object are viscous and elastic at the same time. (G''=G', around 45 degrees)]]> 2022-11-22 13:33:37 UTC https://padlet.com/21014969_2/kd99o1zxmdbs03wv/wish/2394156745