It is not a plastic with very high physico-chemical performance compared to synthetic plastics but it can be useful for DIY.
In any case we will try!
Question: is it biodegradable?
Thanks to ex-océano for this discovery:
former oceanic wrote:(...) There is the chemistry of milk to make plastic materials ...
It's simple : http://dispourquoipapa.free.fr/experiences/ex00018.htm
But here it is without oil and from a non-fossil material ...
Here is the recipe for manufacturing casein-based plastic:
Ingredients:
500 ml of milk
a pan
6 spoonfuls of white wine vinegar or lemon juice
cotton or a coffee filter
a container
Instructions:
In a saucepan, heat the milk.
When the milk is hot, pour the white wine vinegar or lemon.
On a container, put a piece of cotton or the coffee filter then pour the milk-vinegar mixture when it is cooled.
A white matter will appear on the cotton or filter. Remove it gently and rinse the decoupling with water
Press the white material between two sheets of absorbent paper.
Give it a shape then let it air dry at least 2 days.
What is going on ?
You get a hard white matter of casein.
These are the insoluble proteins of the milk representing 80% of the total proteins of the milk. Casein gives the milk a white color.
What is happening ?
The protein of milk, casein, precipitates in an acid medium, that is to say that it becomes insoluble in water (the proof is that the solution recovered in the container is clear). As it dries, the water evaporates and only the protein remains.
At the beginning of the century, it was with this kind of plastic before the hour that we made buttons of clothing.
ps: lots of other experiences to do here http://dispourquoipapa.free.fr/experience.htm
Here is a pretty bluish:
Extraction of DNA from a banana, http://dispourquoipapa.free.fr/experiences/ex00033.htm
), but it's stronger than me. 
it can be very useful for the manufacture of small parts.
