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I'm looking to recycle used eyewear plastic lenses for a sculpture. I want to try to manipulate the plastic to give it a more organic look. I'm also concerned about toxic fumes, so I want to find the best/safe way to do this... if at all possible.

I have several different types of lenses that I'm using. They are acrylic, CR-39 and Polycarbonate.

I've tried putting the c-39's in a toaster oven but it just crackled them to the point where they broke apart.

Thanks

FYI: I'm using the material for a sculpture that I'm creating.

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  • 2
    Related question: Can I recycle plastics at home by melting and molding?
    – THelper
    Commented Mar 6, 2015 at 8:50
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    Why not just donate them to the Lion's Club (or similar local group) that will match them up with someone who needs glasses but cannot afford them?
    – That Idiot
    Commented Mar 9, 2015 at 14:10
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    Because I'm using the material for a sculpture that I'm creating for a eyewear manufacture company. They are also not in the shape of true lense, as they are perfectly circlular and haven't been cut into the lense shape yet.
    – Derek
    Commented Mar 9, 2015 at 20:10
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    Derek, I am curious as to what you find out. I am on the waste side of the optical industry. Optical labs make up for a large amount of landfill space because they don't have a use for their waste. If you can use this waste, which is the plastic ground away to make the lenses, please let me know. Labs pay more money to throw away their waste because they produce so much. They'd be happy to donate.
    – Jamal
    Commented Apr 7, 2017 at 15:44
  • Could you replace them with a different material, that has better characteristics for what you are trying to do?
    – ctrl-alt-delor
    Commented Apr 15, 2017 at 10:52

3 Answers 3

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Both plastic lenses for glasses and for contact lenses could be made from a wide variety of materials. Polycarbonates (PC), polymethyl methacrylate (PMMA), thiourethanes, silicone hydrogels as well as myriads of other polymers come into play. See Wikipedia/Glasses and Wikipedia/Contact Lens. Without knowing more about the materials to be used it will be hard to answer precisely.

Some of those materials, e.g. PC and PMMA are thermoplastic or thermosoftening, thus more or less easily moldable when heated above a specific temperature. Toxic fumes due to chemical decomposition of the polymer as mentioned in the question could of course be an issue. Thermomolding therefore requires extensive air exchange (or preferably outdoor handling only) and careful heating to avoid excessive temperatures. To give an example: PMMA's melting point is around 160°C with the softening starting at even lower temperatures. Decomposing is reported to happen above 545 K (272°C) (see Thermal Decomposition of Polymers) which at least suggests that thermosoftening could be achieved without significant and hazardous decomposing.

PC and PMMA could also be "modified" using solvents such as acetone. Again be sure to take care of precautionary actions wrt to inherents hazards of those solvents (especially flammability and toxicity).

Disclaimer: I am by no means an expert in the field and therefore just reporting my opinion on the subject which should be treated as such.

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  • I've asked the manufacturer what the plastic is but haven't heard back. Thanks for the information.
    – Derek
    Commented Mar 6, 2015 at 0:16
  • I heard back from the manufacture. I put the kinds of plastic in the original post. Thanks again for your help.
    – Derek
    Commented Mar 9, 2015 at 19:43
  • Hmm. I am sorry that I cannot help you any further. Aside maybe the question coulb be asked at Chemistry.SE to get better answers.
    – Ghanima
    Commented Mar 11, 2015 at 10:57
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I would personally go with the solvent technique rather than heat, in my experience you can "melt" abs plastic, accrylic, styro foam, etc. with acetone, just place the lenses aling with the acetone in an airtight container overnight and you should have a putty consistency type goo you can work into a mold or work it with a spatula, as the acetone evaporates away it will reharden hard as a "rock" or should I say plastic ;^) Just make sure you you do it in a well ventilated area preferably outdoor roofed area, and wear eye and breathing protection because acetone can irratate your lungs with prolonged exposure. If acetone doesn't work, try stronger solvents or find out what solvents affect the types of plastic you are working with.

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CR 39, forget about it, it’s thermosetting.

For your project stick to PC(120 deg C) or PMMA. Based on the softening temperature PMMA(70) should be the easiest to work with for a sculpture.

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