Instructable: Make potato plastic.
August 22, 2008 05:58PM
Just saw this go by on the Make Magazine blog (http://blog.makezine.com/archive/2008/08/make_your_own_potato_plas.html?CMP=OTC-0D6B48984890).

Make plastic from potatoes:
[www.instructables.com]

Make better plastic from Hylon VII high-amylose potato starch:
[www.instructables.com]
Note: This version requires a high temperature autoclave or running a pressure cooker WAY beyond normal pressure: "First you need to remove the safety blowout valve". Did you see the episode of Mythbusters where they disabled all the safety equipment on a home water heater and heated it till it burst? It demolished a small house and the shell went 500 feet into the air.
Re: Instructable: Make potato plastic.
August 22, 2008 09:29PM
A relative of mine had a pressure cooker explode under normal use a long time ago (30+ years), there was a lot of damage and severe injury involved.

Water can be superheated by heating it in a microwave, so there's no real reason to risk life and limb to cook a bit of starch. It's OK for the water to boil off anyways.

The process is similar to corn starch Playdough, but has a good science explanation.

(1 part corn starch, 2 parts baking soda, 1.5 parts water, boil and form, then heat cure)

An acid starch treatment step like in the Instructables potato plastic is optional , though Brandon121233 says it increases the strength.


[olytim.blogspot.com]
Ru
Re: Instructable: Make potato plastic.
August 23, 2008 03:40PM
Quote

relative of mine had a pressure cooker explode under normal use a long time ago (30+ years), there was a lot of damage and severe injury involved.

I know someone who was involved in a car accident. There was a lot of damage and severe injury involved. etc etc.

Sometimes, these things happen. That doesn't mean they're necessarily common. Personally, I find the concept of pressure cookers somewhat alarming, but I've never seen nor experienced nor heard of from friends/colleagues/family of an accident involving one til now.

Its just fine to highlight the "first remove the safety valve" sentence and point out what a blindingly stupid idea that is without spreading FUD along the way winking smiley

Quote

Water can be superheated by heating it in a microwave

...but yet I have heard many tales of people coming to grief due to microwaves superheating water which then flash boiled when disturbed.
Re: Instructable: Make potato plastic.
August 23, 2008 04:36PM
LOL! When I was quite young, my late stepfather got it into his head one day to play Tarzan and wrench the top off of a pressure cooker. A bit of food had plugged the pressure valve and he'd noticed before we really came to grief.

The problem with that was that he was torn between not wanting to have our pot roast and vegetables not go completely cold from his having to run cold water over the cooker and wanting to cool it sufficiently so that things wouldn't get out of hand when he removed the top.

He got it wrong. It made quite a noise when the pressure released suddenly.

Amazingly, he didn't scald or otherwise hurt himself with the flying lid. Part of the potroast, several carrots and a few large bits of potatoes did, however, get laminated onto the kitchen ceiling. eye rolling smiley

Edited 1 time(s). Last edit at 08/23/2008 04:37PM by Forrest Higgs.
Re: Instructable: Make potato plastic.
August 23, 2008 04:58PM
I'm sure many pressure cookers are over designed, thus a well built one wouldn't fail at an increased pressure. Some are obviously poorly built, the only way to tell is to use them a few times and be prepared for the potential blast.

I agree that there's always stories floating around, just do your best not to become the next anecdote.
Re: Instructable: Make potato plastic.
August 27, 2008 01:22PM
hmm yes if you cook this in the micro I'd suggest leaving it to cool afterwards for some time would probably be safer than the preassure cooker.

Is this compatible with the instructions?

Any one knows if this is a thermoplastic, i.e. if you can re-melt it after production?

Edited 1 time(s). Last edit at 08/27/2008 01:39PM by mimarob.
Ru
Re: Instructable: Make potato plastic.
August 27, 2008 03:15PM
Quote

Any one knows if this is a thermoplastic, i.e. if you can re-melt it after production?

I'm going to have to guess 'no', based on zero evidence winking smiley

Nature seems to be full of things that set and stay that way, and low on remeltables, wax and pine resin aside. And I don't think you'll find a whole lot of waxy or resinous chemicals in a potato.

But I'll let someone else do the hard work of proving this right!
Re: Instructable: Make potato plastic.
August 27, 2008 04:23PM
You can make PLA from potatoes. Adrian had a student make some as a project and it was on show at the Cheltenham science festival. IIRC you ferment starch to make lactic acid (the same acid that makes fermented milk taste sour). Then I think you have to dry it extremely well and then polymerize it with a catalyst.

So no waxy stuff in a potato but it can make a very good thermoplastic. PLA has the lease warping of anything I have extruded so far.


[www.hydraraptor.blogspot.com]
Ru
Re: Instructable: Make potato plastic.
August 27, 2008 05:33PM
Irritatingly, whilst there are a handful of places that talk about making your own starch-based plastic, nowhere a) gives any serious detail into what actually is or b) tries to remelt it.

One page makes reference to curing the stuff in an oven to harden it up which sounds quite thermosetty to me, but there are a lot of tantalising references to 'thermoplastic starch' across the interwebs... this stuff melts at 156 degrees C and has been used for injection moulding and the like. Not obvious how you make it though, so it probably isn't any more convenient than PLA, and it also needs some serious drying out before use.
I seriously doubt a microwave could superheat water to about 160C, but hey I'll give it a try, yes I do realize it is very dangerous hence the entire page dedicated to safety, and no it is not a thermoplastic but I have been doing other experiments with a purely starch based thermoplastic which I cannot reveal the contents of...yet
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