I wondered if anyone has any links or stories to share about making rigid cornstarch based plastics. I've found only 1 link with a recipe (unfortunately I don't use a microwave and will need to convert whatever the heating needs are to an oven):
I'm looking to do some experiments with casting using cornstarch plastics, especially leveraging its biodegradable properties. I think I remember a product advertised in make of a cornstarch birds nest, it should give you a good idea of my needs.
I'm interested in this as well, and since I do have a microwave (more efficient for boiling water that the stove, so I'm told), I'll try it & see what happens. Also, if anyone has any plant-based plastic recipes at all, I'm all ears.
You can try "milk plastic". (Google for it, there are a lot of recipes and variations on the idea.) While researching this nifty chemistry experiment a few months ago I learned that is why Elmer's Glue has a bull on its label - white glue used to be made from milk. (And I guess they were confused about milk coming from cows, not bulls, but whatever.)
I tried out the cornstarch recipe, and it's really more "creepy-crawler" rubbery than a sturdy plastic. Maybe a stovetop method would yield better results.
I didn't give it a go yet since no microwave but I'm familiar with the use of cornstarch (minus heat) to make a non Newtonian fluid and I think it is trying to build the same.
You can search wikipedia for bioplastic and get some commercial links, but I'm just wondering if there is a chemist out there who, like the biodiesel article has a step-by-step for making biodegradeable plastics.
It starts out looking like the old non-newtonian fluid mixture, but after heating I have a rubbery semi-transparent material.
Transparency suggest lack of crystallinity in polymers, so I'm guessing the heat and water combined disrupted the starch granules to produce a mass of tangled polymer chains suspended in water.
It would be interesting to dissolve a little alum or borax in the water before mixing to see if that changes the properties. The idea is to cross-link the starch molecules, which would produce a more rigid material. (Probably at the expense of fast biodegradation, of course. But that may be reversible depending on pH, exposure to rain, etc.)
your comment about having a bull on the label made me curious, and this is what i found on the elmer's site:
"Elsie the Cow became Borden's very popular "Spokescow" in the late 1930's. She was a big hit at the 1939 New York World's Fair, and soon afterwards the character of Elmer the Bull was created as Elsie's husband. In the late 1940's, Borden's new Chemical Division asked to use Elsie for its new white glue product. The thought of Elsie representing a non-food product didn't seem appropriate, so as a compromise, Elmer was loaned to Chemical as their very own "spokesbull". To this day, Elmer the Bull still represents the most recognized adhesive company."