The idea of using milk to make plastic may sound far-fetched, but this video shows it works in practice. Milk contains casein molecules. This molecule is a monomer, and a chain of casein monomers is a polymer.
The steps of this experiment are provided in the Scientific American
. You will need one cup of milk and four teaspoons of vinegar in order to perform it.
Heat the milk until it's about the same temperature of hot cocoa when you take it out of the microwave oven. Put the vinegar in the mug and just add the milk. Don't forget to use a heat-resistant mug.
Curds, or white clumps, should start to form immediately, as you can see in the video. The milk and vinegar must be mixed with a spoon slowly, for just a few seconds.
After the mixture has cooled, scoop out the curds and use a paper towel to press down on them, absorbing excess liquid. After they're dry, the curds should be kneaded and the resulting dough molded into whatever form you like.
Let the dough dry for 48 hours, preferably on paper towel, and how will have yourself some casein plastic. This may look like a recipe, but for your own safety we advise you don't try to eat it.