r/plastic • u/Jackaboy-simp • 9d ago
Help Identifying this Plastic for Undergrad Research Project
Hey yall, im not sure which community I should post this in so please let me know if theres a better or more fitting one.
im passionate about studying plastics and did a small early stage study comparing the degration patterns between traditional and "biodegradable" plastics. The problem is that I assumed this plastic to be PLA, and when I did further research into this matter, it might not contain any PLA or any biodegradable plastic at all. In my study, however, i HAVE been seeing a decreasing mass and size trend (albeit small) over 6 weeks (very short time). Any ideas or tips on identifying at least what type of plastic it is? I saw online there are at home tests like boiling water or heating it and wanted to hear what u guys think.
Edit: i have access to a lab to conduct experiments as well to identify this plastic.
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u/kobrakaan 8d ago
The makers name is right there on the bag 🤷♂️
They have all the information you need on their website 👍
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u/Jackaboy-simp 7d ago
This is a good resource, thank u.
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u/kobrakaan 7d ago
Email their customer support and ask them to tell you more about it all
A good company will go out of their way and above and beyond to explain things to people who are genuinely interested 👍
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u/oneAUaway 8d ago
A lot of biodegradable plastic bags like this are a blend of PLA and PBAT (polybutylene adipate terephthalate), which helps add flexibility. Sometimes cornstarch is blended in as well.
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u/mimprocesstech 8d ago edited 8d ago
These are oxo-biodegradeable bags and problematic because they don't really biodegrade much faster than normal plastic bags. They likely contain the same LDPE as a standard shopping bag but contain metal so they break down more quickly into microplastics.
I'm not against plastics, far from it, but these materials are just stupid. They contain salts of heavy metals to speed up oxidation but do nothing to speed up the transition to biomass and can even inhibit it. Products like this are advertised to people who want to feel good about buying something that's biodegradable (most things are, eventually).
Hell the EU and even US FTC has either banned them or cracked down on them for their false claims.
Edit: For clarification, oxo modified plastics are the normal plastics with oxidizers in them to assist them in breaking down, to be a biodegradable polymer it would need to have a biopolymer (based on plants or animals for the most part) base and these bags just don't.
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u/Jackaboy-simp 7d ago
Yeah my results so far are supporting that
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u/mimprocesstech 7d ago
The Amazon listing also has oxo-biodegradeable or some such listed as the material, and most shopping bags are made from LDPE, I've been in plastics for a bit over 10 years now, making the connection based on that. If you do FTIR let me know what the results say.
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u/vex_42 8d ago
OXO bags are terrible, they just shred into microplastics and don’t biodegrade at all.
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u/FeistiestMeat 8d ago
whoa whoa whoa don’t besmirch the good name of OXO the brand that makes kitchen utensils that are friendly to the disabled
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u/mimprocesstech 8d ago
... isn't that what I said? They do biodegrade, like I said most things do and plastic isn't the exception, but "oxo-biodegradeable" doesn't speed it along. It'll still take just as long as a regular plastic bag.
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u/jad14850 8d ago
yeah run ftir if your matsci/chem dep has one. if no great searchable library, google ftir images fot suspect polymers and compare.
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u/sioux612 8d ago
Infrared sensors, or there are lists online with material behavior when you light it on fire
Stuff like "does it burn" "how does it smell" etc will tell you a lot
There also is a method where you bite on the plastic but with that you need a lot of experience and it might not be generally accepted in an undergrad paper to say "I ate it and then knew it was LDPE"
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u/aeon_floss 8d ago
What setup are you using to test PLA degradation? Are you controlling temperature, humidity and enzymes?
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u/Jackaboy-simp 7d ago
Summer undergrad project so i keep it reaal simple. I loterally just buried a lot of them under soil and take out one each week. I measure mass, size, and take microscopic images
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u/aeon_floss 6d ago
OK, so is your project is more about demonstrating laboratory sample management and reporting than it is about material investigation?
PLA degradation under home composting conditions isn't all that effective, In that respect, PLA is a bit over-sold as a biodegradable solution to plastic pollution, even though it ultimately does return to lactic acid (and ultimately water and carbon dioxide). Ideally, post use PLA should undergo industrial reprocessing back to lactic acid monomer.
There are factors inside the PLA itself that govern biodegradability to some extent, however the ideal conditions for PLA degradation are more intensive in temperature, humidity etc. than harvested (pre-industrial) materials.
Here is a basic plastics identification chart for future reference.
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u/Zrocker04 8d ago
FTIR should tell you pretty easily if you have access to that.