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PLA/ABS biocompatible for permanemt skin contact?

Posted by gazoox 
PLA/ABS biocompatible for permanemt skin contact?
October 30, 2015 05:20AM
Is PLA/ABS biocompatible for permanemt skin contact (allergic reactions, inflammation, long term chemical diffusion,..)? Which hazards are known?

How are these plastics are evaluated? In general they should not contain any softener chemicals like phthalate, but who knows..
I could not find anything helpful... Some "adult play toys" are made of ABS and does not seem to have negative effect.


O Can they be used to print, for example, eye glasses side frame parts, who have permanent skin contact?
O Are there any varnish anyone can buy to make a designfull finish (transparent/gloss/semigloss/coloured) without hazard for human for permanent skin contact? (I found acryl varnish for kids toys, but still having doubts against.)
Re: PLA/ABS biocompatible for permanemt skin contact?
January 26, 2016 12:03PM
Quote
gazoox
Is PLA/ABS biocompatible for permanemt skin contact (allergic reactions, inflammation, long term chemical diffusion,..)? Which hazards are known?

How are these plastics are evaluated? In general they should not contain any softener chemicals like phthalate, but who knows..
I could not find anything helpful... Some "adult play toys" are made of ABS and does not seem to have negative effect.


O Can they be used to print, for example, eye glasses side frame parts, who have permanent skin contact?
O Are there any varnish anyone can buy to make a designfull finish (transparent/gloss/semigloss/coloured) without hazard for human for permanent skin contact? (I found acryl varnish for kids toys, but still having doubts against.)

Natural PLA (no dye/pigment) should be fine if it hasn't got any other additives (I don't know whether it does or not). Its monomer is lactic acid which is innocuous and produced in the body anyway. Depolymerisation seems unlikely when in contact with skin as sweat is slightly acidic. Even if it does happen, it would be a very slow process (and any resulting irritation likely negligible). Sensitization can never be precluded but because lactic acid is "endemic" to the body, I'd rate chances of that very low. Leftovers of the polymerisation initiator might pose an issue, although these are used in tiny amounts in the first place, so any potential risk would be lowered in proportion to the fractional molar concentration used. These details should be possible to look up on the web.

A priori, I would have more concern about ABS because remaining monomers could slowly leach out. This would be an extremely slow process, and not an issue at all for daily occasional contact but if you're talking permanent contact, a different yardstick is applied: the safe exposure limits suddenly become much lower (this may well be over-cautious, but that's how it is). Styrene has recently been classified as dangerous to reproduction. I think butadiene is a suspected (or confirmed?) carcinogen. Exposure to these from properly cured ABS should be minimal and not a worry, however if you're trying to commercialise a 3D printed ABS product which will be in permanent contact with skin, I would be careful and make sure you tick all the regulatory boxes. In short, I would say (but don't quote me on that) PLA is a safer bet than ABS.

Another issue would be that even if you source PLA or ABS certified for your use, you're then putting it through a hot extruder, which is likely to change the specs of the plastic (depolymerization/partial decomposition) and invalidate any certification that came with it...

Just some thoughts...

Bart

Edited 1 time(s). Last edit at 01/26/2016 01:27PM by bartdietrich.
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