This week, I was finally able to determine some material properties of the bioplastic I’ve been making. As a reminder this bioplastic is intended to replace single-use plastic products in the Philippines to decrease pollution.
I took samples down to the Instron machine and conducted tensile testing. I tested 13 samples, and recorded force vs. displacement data for each of them until they broke. So far, I have used this data to calculate tensile strength and percent elongation. I plan on conducting the rest of the calculations suggested in the ASTM standard D638, but have been spending my time since creating more dogbones as they are time senstive.
More dog bones:
Upon successful results from the first tests, I am now going to test a variety of other samples to compare them to. See below:
Plastic bag dog bones:
While I can look up the values online, I want to also test oil-based plastic to confirm the values and eliminate any variation presented by the machine. I have cut 4 dogbones each out of a grocery store plastic bag (HDPE), produce bag (HDPE), and a Ziploc bag (LDPE) to test on the machine.
Cutting oil-based plastic dogbones to test
+2, +3, +4 minutes dog bones:
In my first round of testing I cooked the plastic for 1 minute after it had started to coagulate. However, during my initial testing at the start of this semester, I learned that the longer I cooked the plastic for, the stronger it got. So I created dog bones that were cooked for 2, 3 and 4 minutes past coagulation, that I will test on the Instron machine next week.
Dog bones at varying cook times
Cassava
Another material we’ve learned some companies use for bioplastics is cassava. However, I had to make my own starch. Using a video Lizzie found online, I followed instructions on extracting the starch from the cassava root. The process involved blending, straining, and lots of waiting, but after 2 days, I finally had cassava starch. I used this starch to create dog bones too, varying the cooktimes from +1 minute to +4 minutes.
Making cassava starch
Cassava starch settling in a bowl as it seperates from water
Cassava starch – final product
I am currently having issues with removing the dogbones from the molds. They are quite sticky, and tear easily when I try to pull them up. Hopefully letting it dry a bit longer will help.
Fieldwork Samples:
Moving on from the dog bones, I am going to bring samples of the bioplastic I’ve made on fieldwork so we have something to show the people we meet with. My initial thought was a larger, 220mm x 220mm square, however, after the first two samples ripped upon removal, I decided to create four smaller 95mm x 95mm squares. These are working better, and I have created samples from both corn starch and cassava starch with various cook times to bring on fieldwork.
95mm x 95mm samples drying
In addition to the work listed above, I have continued to research potential companies to meet with during fieldwork.
Moving into next week, I intend to finish testing the dog bones, begin analyzing the data, finish creating square samples, and add more companies to our list of people to meet. All before Wednesday when I leave for fieldwork. I can’t wait!
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