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Hi!
I’m a senior student in a science high school in the Philippines. We are required to make an investigatory project, and my group mates and I thought of making bioplastic from cassava (Manihot esculenta) sap and chitin from leftover crab shells. We gathered lots of information from different materials, mostly from the Internet. Just two weeks ago, we came across a video in YouTube and we thought that we can pattern our methodology from the one used in the video. That video was the one featured in your website.
Here is one of the procedures, as well as the materials we used in our experiment. By the way, we used crushed crab shells.
Methodologies:
- Extraction of Chitin (from Crab shells)
1. Dilute solution of sodium hydroxide (1-10%) at high temperature (85-100°C)
2. Demineralization (treating in a dilute solution of hydrochloric acid (1-10%) at room temperature)
3. Decolorizing process – obtaining white chitin (organic solvents/very dilute solution of sodium hypochlorite)
Depending on the severity of these treatments such as temperature, duration, concentration of the chemicals, concentration and size of the crushed shells, the physico-chemical characteristics of the extracted chitin will vary. For instance, the three most important characteristics of the chitin i.e., degree of polymerization, acetylation and purity, will be affected.
We tried doing it, but didn’t get any good results. We expected to also see the clear paste we saw in the video, but all we got was a yellowish, sort-of viscous liquid. After the experiment, we tried weighing things down, and came up with the following:
1. We have read what chitin is, but we’re not sure what it really looks like.
2. And since we don’t really have a clear idea on what chitin is, we weren’t able to make the bioplastic.
Now, we thought of asking help from you and the other guys featured on the site. We really want to be successful in this, because this project was chosen along with a few others to represent our school in an upcoming local science fair. Do you have anything to say about our methodology or materials that made our trial a failure?
We would really appreciate it if you would help us. If we did it right, we’ll let you know what the results are. Thank you very much! :)
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Discussion 
Comments
First, let me tell you that I think it's great that you are taking on this project.
However, my first reaction is that chitin is very difficult to work with, because it is insoluble in most solvents. It is insoluble in water except at extreme pH's. It is soluble in some very toxic organic solvents, and bioplastic films CAN be cast from such solvents, but attempting this is not recommended for anyone except trained chemists.
To answer your question about chitin, by the way: pure chitin is a white powder or a white granular material; impure commercial grade chitin is a light brown granular material.
However, even if you get pure chitin, it would not be compatible with the starch in the cassava extract.
One suggestion is to simplify the formulation to JUST using the cassava sap. The sap will contain a lot of starch, plus some other things, including some proteins. Your project could be to see if you can get a bioplastic from the cassava sap even with its non-starch components. The procedure to do this would be more similar to the video. And you still might have to do some experimenting to get the best result possible.... which could prove very interesting to document, as you go through different trials.
Obtaining a bioplastic from crude cassava sap (i.e., without extracting the pure starch) would be a major accomplishment, that should definitely get you noticed at the science fair.
Good luck with your project, and let me know what you end up doing. Especially if you end up finding a variation that is successful, I would love to hear about it. If you do have success, you might even be interested in making a video of yourselves making it for the website?
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