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To find the best plastic to make our disposable tableware, we had to make an empirical approach. But what does that mean? It is, in our context, when you do lots of experiments to see what would be the best plastic to do carving sets. So we did that, and after each experiments we noted the pros and cons of the plastic. We saw each time what we could do better, and we did hypothesis about how to improve the weak points of our plastics. However, this type of approach requires a lot of experiments and is not always effective.

First we compared potato starch and cornstarch to find which one would allow us to obtain the best plastic. Then we made experimentations to find the perfect quantity of oil to make waterproof plastic. After we compared what sort of mold could be the best for our tableware and finally, we tried to adjust the recipe to obtain an hard plastic.

Background picture: Solène mixing the plastic while Louise is filming her.

Icon: Solène mixing the plastic (again)

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Here is the basic protocol we'll be using as a reference protocol in our experiments :

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Here is the basic protocol we'll be using as a reference protocol in our experiments :

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Equipment list :

- 100 mL beakers
- Heater
- Pipette and propipette
- Graduated cylinder
- Potato starch
- 50% glycerol solution
- Distilled water
- Food coloring
- Balance
- Pan and whisk
- Glass stirrer
- Spatula
- Cup
- Ceramic plate

Protocol:

- Put 100 mL of water in a pan.
- Add 2 mL of glycerin and stir with the whisk.
- Next, gradually add 5 g of potato starch while continuing to stir, adding food coloring (optional).
- Heat this mixture until it becomes translucent. When it becomes translucent , continue to heat over low heat while stirring for 10 minutes.
- Pour this mixture (still warm and liquid) on a plastic support (or glass) on which it can easily peel off by spreading a thin layer on its surface. (later on, we will simply pour it into molds).
- Make the plastic dry at room temperature for about a week.
- Once dry, the plastic can be taken off.

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Here's a photo of our equipment (from left to right): glycerol solution, potato starch, distilled water, cornstarch (other products were not used)

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Experiment n°1: Choosing between potato or corn

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Experiment n°1: Choosing between potato or corn

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Using the basis protocol mentioned above, we first wanted to know what would be the best kind of starch for creating plastic.

To make some biodegradable plastic we have two possibilities, we can use either:
- cornstarch
- potato starch

Each of them are completely natural ingredients and are widely used in kitchen.

We followed the protocol, using those quantities: (to identify them, we have put specific tints in each plastic)

-Our first plastic was made of 5g of cornstarch, 2mL of glycerin and 100mL of water (purple)

-The second was composed of 5g of potato starch, 2mL of glycerin and 100mL of water (light blue)

After having creating those two plastics with both types of starches and having flowed them into the hollow side of plastic picnicware forks we could observe some differences between them:

- The first one contained lumps during the heating and he had a jelly texture and on top of that we had difficulties to pour it into the mold. - The second was better because we were able to pour it easily into the picnicware and it didn't have any lumps.

Assessment :

We observed how thoses plastics evolved, letting them dry for a week. We noticed that the two forks were too brittle, too thin, they tore and deformed. This means we'll have to change the molds, and also to find a recipe which can make the plastics stronger. However, we decided that for our next experimentations we will use potato starch because it is easier to mold it.

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Photo of the fork made with cornstarch. We can see that it bended while drying.

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Photo of the fork made with potato starch. We can see lots of imperfections.

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Photo showing how flexible the plastic was.

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 Hypothesis 1: Improving our plastics by adding oil                                                                                                              Experiment n°2: 

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 Hypothesis 1: Improving our plastics by adding oil                                                                                                              Experiment n°2: 

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We know that our plastics, made of starch, are not waterproof. By adding some oil these one should be more resistant to water, so we created two differents plastics with the basic recipe, but adding different quantities of sunflower oil (a completely natural product).

-The first plastic was composed of 5g of potato starch, 2mL of glycerin and 100mL of water,plus 5,O mL of oil (red)

-The second plastic was composed of 5g of potato starch, 2mL of glycerin and 100mL of water plus 1,0 mL of oil (light green)

Then we poured them into the hollow side of plastic spoons. The texture was very easy to pour, also very sticky, but the red one wouldn't stay in place because of its oily texture. However, those plastics were waterproof. We tested that ability by putting a little bit of each plastic into a beaker filled with water and agitating it. We didn't notice any degradation even after 10 minutes.

Assessment :

After two weeks of drying, the two spoons were simply "gone" from their molds, they had dried and formed little flakes outside of the spoons. In our further experiments, we'll have to reduce oil quantities, if we still want to make it waterproof, and we have to find another way to mold our plastics.

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A video showing the texture of the plastic while making it.

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The plastic didn't, either, stayed into the molds. However, with less oil, at least it formed a kind of plastic sheet.

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Here is the result of our "oily" experiment. There was way too much oil and the plastic didn't stay into the molds.

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Second Hypothesis : Improving our plastics by creating proper molds                                                                          Experiment n°3:

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Second Hypothesis : Improving our plastics by creating proper molds                                                                          Experiment n°3:

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We have to find the mold which will facilitate the demolding of the plastic and with which we will obtain the best tableware. We created different types of molds, some in modeling paste, others in salt dough, for forks, knives or spoons.

To make those molds we simply used regular metal tableware, pushing them onto the pastes to obtain molds. Then we made twice the same plastic, using the basis recipe:

-The first plastic was composed of 5g of potato starch, 2mL of glycerin and 100mL of water,plus 0,1 mL of oil (yellow). A part was put in the modeling paste molds, another part into the salt dough molds.

-The second plastic was composed of 5g of potato starch, 2mL of glycerin and 100mL of water, without oil (dark green). As above, a part was put in the modeling paste molds, another part into the salt dough molds.

We didn't face any difficulties to put the plastics into the mold. Plus, even with the low amount of oil, the yellow plastic was still waterproof.

Assessment:

After one week of drying, we notices that the plastic which was into the modeling paste crinckled and shattered, but had a solid texture. Yet, the salt dough molds were a failure, because the plastic mixed with the dough and was impossible to demold. The choice was evident, the best type of mold is the mold in modeling paste.

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The salt dough molds.

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The modeling paste molds.

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The salt dough molds mixed up with the plastic. It was impossible to demold.

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The result of the modeling paste molds. You can recognize the shape of a fork, however, it is clearly not usable to eat.

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Third hypothesis : How can we improve the molds ? 

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Third hypothesis : How can we improve the molds ? 

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At that time, we had to improve not only our molds but also our recipes. We wanted to obtain an harder and stronger plastic, which could be used for actually eating food.

So we made up several modeling paste molds, one for forks, one for knives, and one for sticks (we hoped it would be simpler to mold and dry). Than we tred to increase the basic quantities of potato starch.

-The first plastic was composed of 7g of potato starch, 2mL of glycerin and 100mlL of water(orange). It was put into the sticks molds.

-The second plastic was composed of 10g of potato starch, 2mL of glycerin and 100ml of water (baby blue). It was put into the cutlery molds.

-The third was composed of 15g of potato starch, 2mL of glycerin and 100ml of water (purple). It was put, as well, into the cutlery molds.

We noticed that the texture was easier to put into the molds, and we increased our production, being more effective than before. We tried to dry the plastic using a hairdryer, but it made the plastic, as well as the mold, melt. We took the plastic in our classroom in order to observe their evolution during the days.

Assessment:

This time, as we were able to observe the plastic dry during the week, we could see it started to retract and crackle. However, it had quite an interesting hard texture, especially the one with 10g of potato starch.

We imagined other moulding techniques during the week: like compressing the plastic with an another mold inside the first mold to prevent it from retracting. We can also try to place on top several layers of plastic, as it dries, or even don't put the plastic into molds and trying to obtain thick sheets that we could cut into cutlery. We even found some spoons silicone molds in a cookery shop that we could test.

So during the next week, we made other plastics. We added vinegar because its acidity should help to dissolve the starch into a solution (we needed to test that hypothesis).

-The first plastic was composed of 10g of potato starch, 2mL of glycerin and 100mlL of water (light blue). It was put into the silicone molds, then on a ceramic plate. We pressed some of the spoons with another mold above it.

-The second plastic was composed of 10g of potato starch, 2mL of glycerin and 100mlL of water, plus 3 teaspoons of vinegar (light green) . It was put on a ceramic plate.

It was easier to mold with the silicone molds, and making flat sheets of plastic was easier too.

Assessment:

During the week, we saw that the silicone molds spoons retracted, but the ones which were pressed didn't dry so we got holes into the pressing molds, but it didn't work either. The blue plastic on the ceramic plate made a brittle, but clear, smooth and thin sheet. The vinegar green plastic became distorted but it was the perfect texture, nearly unbreakable!

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Plastics just after being molded.

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The brittle sheet of blue plastic.

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The hard "seaweed-like" plastic.

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Fourth hypothesis : looking for the perfect recipe 

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Fourth hypothesis : looking for the perfect recipe 

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We had resolved several problems such as water resistance, hard texture and strong plastic. However, we weren't able to mold them into proper cutlery. During next weeks we tried other recipes, but no significant change was observed.

We observed mould growing on some of the plastics. We believe it is normal given that the plastic is starch-based.
We tried to change the proportions to test them, but the plastics were still not producing any proper results after being molded into modeling paste molds or put on cereamic plates. Here is a few recipes we tested:

- 15g of potato starch, 3mL of glycerol solution, 100mL of water (yellow)

- 15g of potato starch, 5mL of glycerol solution, 100mL of water (electric blue)

- 15g of potato starch, 10mL of glycerol solution, 100mL of water (green)

- 20g of potato starch, 3mL of glycerol solution, 100mL of water (purple)

- 20g of potato starch, 5mL of glycerol solution, 100mL of water (orange)

- 20g of potato starch, 10mL of glycerol solution, 100mL of water (grey)

We even tried to make plastic at home. The last recipe tested had quite good results. We were able to create the tip of a spoon, hard, waterproof and usable. However, the stick detached itself. Here is the recipe used:

- 15g of potato starch, 3mL of glycerol solution, 150mL of water (white)

These experiences proved that we are far from the result. We would've used to extra times to do experiments. However, we acheived to improve the basic formula, so it's not a complete failure.

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Here is a jelly-like plastic, but it crinkled while drying.

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Making the green plastic.

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Here is two pieces of spoons made at home, which had the perfect texture.

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Two examples of homemade plastics.

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Go back then to the table of contents...

http://padlet.com/CillyKarma/prodfin1S2

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How to make biodegradable plastic disposable tableware

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(or in French : Comment fabriquer de la vaisselle jetable en plastique biodégradable?) A very fine TPE by Louise Duhamel, Solène Chédru, and Léa Lo Van, all of them in the (best) class of 1ère S2 at lycée Notre Dame d’Espérance in St Nazaire.

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... Or continue to the next page!

http://padlet.com/CillyKarma/prodfin1S2part3

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Finally, what we have learned and what we have acheived.  By Louise Duhamel, Solène Chédru, Léa Lo Van (group n°25), 1ère S2 for TPE 2014-2015 at Lycée Notre-Dame D'Espérance in St Nazaire.