With water, corn starch, vinegar, and glycerin, you can whisk, spread out, and dry a sheet of bioplastic, a biodegradable plastic-like substance created from biological materials instead of petroleum. This Science Luxembourg video provides instructions for the activity:
Add 1 tablespoon of starch and 1 teaspoon of vinegar to 4 tablespoons of water in a cooking pot. Add also 1 teaspoon of glycerin. You can get the glycerine in a pharmacy. If you want to make more bioplastics, you can double, triple, etc. the quantities.
Stir the mixture thoroughly with a whisk and heat over medium heat. Always keep stirring.
After a few minutes, the mixture becomes thicker, you have to then replace the whisk with a wooden spoon to continue stirring.
After more or less 10 minutes you have a sticky and glassy substance in your cooking pot. You can then spread this substance on a baking tray or another suitable surface.
Wait at least 24 hours for the bioplastic to dry. Then you can pull it off the baking tray.
Safety reminder: The spreadable mixture will be hot and sticky. Be careful of burns.
Experiment variations: More glycerin creates a softer bioplastic; less creates a more brittle bioplastic. If you don’t have glycerin handy, try cooking oil, which reportedly doesn’t work as well, but can sub-in in a pinch.
What’s the science behind this activity? From Science Lu:
The starch that serves as a raw material in this experiment consists of very long molecular chains, many of which are branched. In order to produce bioplastic from it, the starch must be boiled with vinegar. A chemical reaction takes place in which the side branches of the molecular chains making up the starch, are “cut off”. The results are long starch molecule chains (which can be compared to cooked spaghetti).
The effect of the third ingredient, the glycerin, can be explained well with the “spaghetti model”: long, damp spaghetti stick together and get stuck. Transferred to the bioplastic, it would be rigid after drying and therefore easily fragile. The oily glycerin serves as a “lubricant”, the spaghetti or the long starch molecules can glide past each other. The bioplastic softens and stays flexible even when it has dried.
Next, create a bioplastic bowl with the addition of a piece of fabric, two bowls, and scissors. Watch the demonstration:
Can replacing plastic with biodegradable materials, mixed with reducing all types of plastic use, solve the world’s plastic problem?
For a more complex exploration: Ensia’s Are bioplastics better for the environment than conventional plastics?
Next, learn more about plastic with these videos:
• MarinaTex, a bioplastic made from fish waste
• How to turn milk into plastic
• Sixteen year old Elif Bilgin turned banana peels into a bioplastic
• Plastic Was Invented To Replace Bugs
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