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Recently Ankur Sharma wrote to us:
Hello, I really appreciate your effort to make these videos and information
But i was thinking of making corn plastic utensils (glass, plate, knife etc.).
I would really want some tips from u. do i need molds. If i put the materials in a mold after cooking to let it dry, is it going to work. will i have plastic in shape of the mold. what should be the proportion of glycerin:vinegar if i want my plastic to be hard and not very flexible.
Also can i use the process which is used in the youtube video - How to make bioplastic(extended version)
or do i need more materials
i am awaiting a reply eagerly.
Thanks and again really appreciative work. Well done!
Thank you for your letter, Ankur!
First, I want to start out talking about some basic definitions.
When you hear about commercially-produced "corn plastic" utensils and cups, generally you are hearing about bioplastic that is based on the polylactic acid (PLA) polymer. Polylactic acid is polymer that is created by polymerizing lactic acid molecules. In simple English, PLA is a long chain molecule that is created by linking (polymerizing) a large number of lactic acid molecules together. The lactic acid is created by fermenting starches and sugars, and most commonly corn starch is the source for these commercial products. Thus, these products are called "corn plastic" or "corn starch plastic".
The sequence of events in the commercial creation of this kind of plastic is therefore as follows:
- Complex starch from potatoes, corn, fruits, or other starchy plants is broken down into sugars using enzymes
- The sugars are fermented into lactic acid using bacteria.
- The lactic acid is purified
- The pure lactic acid is polymerized; in other words, the individual lactic acid molecules are chained together to form polymer molecules that will form the basis of the bioplastic.
- The poly-lactic acid (PLA) is refined, combined with other ingredients such as plasticizers and additives to produce a bioplastic resin, or bulk plastic material.
- Finally, the bioplastic resin is processed so that it can be molded into the shapes of the final plastic products.
(Image to the right is from Toyota Corporation.)
All of this chemical processing is far beyond what you can achieve in your own home, although you can read and learn a great deal about this process on the web. For some of the basic chemistry of PLA polymerization, I would even recommend Wikipedia: Polylactic Acid.
So what can you make in your own home? You can make plastic from starch in your own home. However, the polymer basis for the plastic will not be PLA, it will be the starch itself.
Yes! Starch is a polymer molecule. Specifically, it is a type of polysaccharide. Whereas PLA is composed of a long chain of Lactic Acid molecules, starch is composed of a long chain of glucose molecules. When you are making "starch plastic" using the instructions that we provide on this site, or in Brandon's video, you are using the actual starch molecule as the polymer chain in the material.
Q: If starch is already a polymer, why do commercial companies go through all of that trouble (the steps above) to convert starch to PLA? Why not just make starch utensils?
The problem is the starch, by itself, does not make a very sturdy plastic. You can make thin flexible films that can be very useful, but it is generally too flexible and too weak to make solid objects like cups or utensils. For the most part, starch plastic is good for making wrapping material, packaging, and coating films. This is why "corn plastic utensils" means "PLA utensils" and not "starch utensils"... even though the PLA originally is made from starch to begin with!
Uh oh. So where does that leave you?
Unfortunately, it means that you may have to alter your plans slightly if you want to make your own bioplastic utensils. That is, you probably don't want to start using starch as your biopolymer.
Fortunately, however,there are other biopolymers that you can use in order to make stronger, harder bioplastics in your own home. My recommendation would be to start with gelatin as your polymer, and to follow our ingredients and instructions in these articles:
Home-made bioplastics sword (gelatin biopolymer)
Bioplastic by Da Vinci (gelatin biopolymer)
Both of these articles provide specific formulations for hard, inflexible plastic objects, which should be good for your goal of making utensils. In either case, you will want to make sure that you make the mold first, and that you leave enough time for the plastic material to try once you have poured it into the mold.
If you are not satisfied with your results using gelatin as a polymer, you can also use agar. The recipe and instructions are here:
How to: make algae bioplastic (agar biopolymer)
This is a very popular formulation that produces very good results, and by manipulating the amount of sorbitol that you include you can make it harder or more flexible, depending on your needs.
Good luck with your project, and happy experimenting!
Remember, if you have successfully made bioplastics using our recipes or suggestions please send photos or video to
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Discussion 
Comments
Thanks very much for quick reply!I think this is really helpful.
I want to ask a few things before i finalise the idea of making utensils with gelatin plastic.
Is gelatin available on any local store in Norway? Is glycerol same as glycerin?
Which one is better for making utensils (plate, glass, knife) agar plastic or gelatin plastic?
Can i use the same procedure as in the quesetion of making bioplastic swords?
Is the plastic going to be waterproof or should i remove drinking glass from my plans?
THanks
plz reply
Ankur
"Glycerol" is the term that usually just means "glycerin in the form of a solution in water." You can usually buy pure glycerin or sometimes glycerol. Try a local drug or grocery store, or I know that if you simply google "buy glycerol" there are a number of mail-order options online.
As far as which one would be better for your PARTICULAR application, I'm afraid this is where the "science project" of your project really comes in: you're going to have to try it out yourself! Do a little experimenting, it should not be too expensive to do it in small amounts with different recipes, and then you can test the resulting product and see. You probably will have to experiment a little bit anyway, because you may find that you want to slightly increase or decrease the relative amounts of plasticizer, depending on how you like the end result.
And finally: the end result will NOT be water proof. A drinking glass would be.... well, maybe ok as a single-use only drinking glass?
You people are genius!
If you want, I can make a tutorial for making gelatin bioplastic and you can post it in your webiste
I am pretty impressed with your work.
1) What is the biodegradabilit y of PLA utensils?
2) If you are familiar with the southern invasive vine called Kudzu...do you know it's viability in making variations of bioplastics?
- Cheers
Hi there! Thank you for your questions.
1) Most of the PLA utensils that you can buy commercially are pretty sturdy, and you can use them easily for stirring liquids or any other normal plastic utensil use. The main difference from normal plastics is that you can compost them, so that over a long period of time and exposure to sub, water, and microbes it will decompose.... eventually. But you don't have to worry about it dissolving in your coffee.
2) This is a really interesting question. I wasn't familiar with Kudzu before now, although I've just done some preliminary reading and research on the web. It seems like it's a perfectly good source for starch, and in fact I would BET that you could use kudzu starch extract that you buy in a store to make home-made bioplastic using the same basic recipe and process that we have posted on this website. Just substitute the powdered kudzu extract instead of potato starch or corn starch.
However, if when you say "viability" what you mean is "large scale commercial viability"... that's another question altogether, and I don't know the answer. How kudzu would fare on the commercial market would depend on the costs of harvesting the kudzu and extracting the starch from it on a mass industrial scale, as compared to what those costs are for other sources. I don't know off-hand if any research has been done on this but I can look into it.
Thanks for the interesting question!
--Greg
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