Polycarbonate is prone to environmental-stress cracking (ESC) in the presence of certain oils and liquids.
Among two main approaches to suppress this are:
(i) copolymers with small addition of another polymer into PC
(ii) PC reinforcement with nanoparticles, which are the state-of-the-art solutions that are being explored, keeping in mind that the glossiness and dimensional control as key attributes of PC need to be preserved.
Neither of these are really good options and I couldn't recommend either of these as they are strictly band-aids. Polycarbonate coatings (silane surface treatments) are a better way to enhance chemical resistance - but - are not a complet solution. It is better to choose a more applicable resin. Amorphous PET if you need clarity...
Chhiu-Tsu Lin 4.02 Northern Illinois University - ChemNova Technologies, Inc.
For environmental protection of PC and PET, we have developed two organic-inorganic hybrid nanocoatings - Q1 (base coat) waterbase thermal cure with strong bonding strength to PC/ABS, PET, and metal surfaces; Q2 (hard coat) waterbase thermal/UV dual cure with an pencil hardness 4H on PC/ABS and PET. Both Q1 and Q2 display excellent optical transparency of 98%. A combination of Q1/Q2 coating gives a hard yet flexible surface on PC/ABS and measured to have an increase of elongation strength.
Dear Matthew and Chhiu,
Thanks for your input!
I'm working on bulk PC using injection molding. Even with very low levels of residual stress (far below yield stress), the rather open porous structure of PC causes uptake of oils from the atmosphere, resulting in cracking and eventually failure. That is the very reason, I consider the aforementioned approaches as promising. I've learned that small amounts of PA can be of help.
Does someone have any knowledge of post molding dipping (for pore closure) as a quick, reliable step?
I'll highly appreciate your take on these issues.
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