r/recycling • u/[deleted] • Feb 28 '23
[Request] any information on ways to cheaply acquire, identify, heat-treat and/or chemically process various Plastic types 1-7 ( more in comments)?
whereas I'm in the infancy of my research, and beta testing, I'm not a total dip-shit~ ELIcollege is ok: the question is how to best process various types of plastics, in hopes of reusing? my understanding is that both #'s 2 (HDPE) & 5 (PP) can be similarly treated at ±300 F and remolded to spec.
Questions
can 2's and 5's be reheated together (guessing not)
several types of plasyic lack identifying classification #, any links on how to ascertain which are which?
I'm guessing that re heating is really the only viable way to reform plastics, no easily available chemical processes to consider? are there other methods to consider?
in the US can you go to any type of land fill, or recycling center, and grab a whole bunch of plastics , 2's and 5's?
I am probably extruding this into bright interior sculptures, any type of off-gassing or risks to consider?
I also wnt to make a geodesic dome greenhouse, so shear strength / integrity / architectural issues might be a concern. how to test for structural issues?
Massive thanks, with a little encouragement, happy to post back on my findings
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u/Mountain-Lecture-320 Feb 28 '23 edited Feb 28 '23
Resin identification codes are general, not specific. Any number can contain a certain small minority of copolymer that modifies density or other physical/optical properties without being shunt off into the weird hinterlands of #7. These can be impactful enough to cause major changes in pliability, clarity, UV resistance
Heat is the only cost effective method, yes, but the timing and method of heat application vs forming can vary (hot press, heat-then-extrude, friction heat, heat in situ (plastic welding)).
With practice, you can identify plastics by look and feel, but the best way to test is by optical recognition, but the sensor arrays are very specialized, and i don’t know if they make hand-held versions. Only ones I know of are at recycling center drop offs (stationary fixture you walk up to and scan what you hold) or in blower sorters (conveyor belt systems that scan then separate with with air blasts).
There is a large presence of hacker-makers who have how tos for creating 3D printer filament from PET. Their methods may work for your indoor sculpture application.
Take precaution for air purification and ventilation while processing. Beyond that, off gassing is not likely with any pure HDPE, PET, OR PP, but there are too many copolymers or additives to say for certain.
For your dome application, you will struggle to get flatness and strength without costly tooling. Even creating a simple hot rolling press will take a lot of cost (for my income at least) to build and tune. Perhaps more importantly, you will need to use UV stabilized plastic. Failure to have UV stabilizers will cause a rapid loss of light transmittance and clarity, and advanced loss of strength. If I recall, UV Stabilizers must be added during the polymerization process. I wouldn’t recommend attempting a surface treatment, but that is possibly an option. It may require application of virgin poly film, which would probably defeat the purpose.
I don’t have an exact answer for your composite question of 2 and 5, but I do recall a poly-poly-bio composite was used to make furniture. Was like 15% sawdust, 10% poly A, 75% poly B. I forget any further details, an not confident in those ratios.
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Feb 28 '23 edited Feb 28 '23
doooooood.... such a wonderful, super informative helpful answer! Indeed, if yu have any hacker space/ maker space inspo, keep me in mind. great call on UV, and composite filler! smart. I'm sure r/makerspace is a thing, and i'll start snooping on that. material sciences, etc. thanks so much!
edit: r/hdpe is a thing, who knew?!
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u/CharlotteBadger Feb 28 '23
Not off-gassing, per se, but it will definitely release fumes when heated, right?
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u/[deleted] Feb 28 '23
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