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Richard Rumancik
09-07-2012, 12:30 PM
I have a customer for whom I have been making a part for a number of years. It .010" polycarbonate (Lexan 8B35) and I apply black paint and then 3M PSA tape before laser cutting. The customer wants the part to be black, and polycarbonate only comes clear.

I have been painting the back of the sheet using Nazdar solvent-based screenprint paint, but I am out of paint and am looking at alternatives. The ink is very unpleasant to work with (high VOCs). As I only need maybe 6 panels 25" x 16" I can't seem to get any screenprint manufacturers interested in this small job.

I have tried spray paints including those designed for plastics but have never been able to achieve good adhesion of the paint to polycarbonate.

I am also going to try some "fast sign" shops but don't think that polycarbonate is that common for signs. It is often used for decals on commercial equipment (graphic overlays etc.) I'm also wondering about digital printing but don't know if this is suitable for that process.

Does anyone have any suggestions as to how I could color the backside of the polycarbonate or what paint would adhere well?

Mark Sipes
09-07-2012, 12:42 PM
Do you know anyone in the automotive paint department. Many panels on cars are made of Lexan (GE polycarbonate) and a simple paint booth and 5 minutes of spray should do the job...

Michael Hunter
09-07-2012, 1:22 PM
Radio controlled model cars often have Lexan bodies and model shops sell a special spray paint for them which stays on perfectly.

Model shops are notoriously expensive, but it might get you out of a hole.

Kim Vellore
09-07-2012, 1:28 PM
I have used lacquer paints which seem to work well for me, not sure your definition of adhesion, do you want it to stay with rough handling or just survive the pulling of the tape over the paint?. it comes in spray cans available at auto shops. It is a carcinogen so use with proper PPE.

Kim

Tucker Alford
09-07-2012, 3:36 PM
Krylon Fusion works really well with plastics. I've masked, painted & removed the mask with no paint damage.

Richard Rumancik
09-07-2012, 8:23 PM
Thanks for all the suggestions. I don't know if I could get an autobody shop interested unless they had the right paint in the gun - it is kind of a nuisance job for them as well. If I could get RC paint in larger cans it would be viable but the cans tend to be small and expensive in proportion. But I'll still check more on that possibility as the alternatives are expensive too. I'm pretty sure Fusion was one of the "plastics" paints I tried but did not work that well. I might try the lacquer based paint. Kim, it is not specifically rough handling I am worried about, but if a peeling action is applied to the polycarbonate I want it to fail at the adhesive joint, not at the interface between the paint-polycarbonate.

With the spray paints I tried the paint would flake off and stick to the 3M pressure-sensitive adhesive, which means that the bond between paint and polycarbonate was not good enough.

I'll keep looking at the auto-supply shops, hardware and hobby stores.

The manufacturers of the polycarbonate film suggest several rather exotic paints for Lexan which I am sure would cost a small fortune and be difficult to get/ship/apply. Even the screen printing paint I used cost something like $75/litre and then I had to buy a jug of solvent as well.

Joe Pelonio
09-07-2012, 8:36 PM
Go to the auto parts store and pick up a rattle can with automotive touch-up paint for $5-$7.

Scott Challoner
09-08-2012, 12:38 AM
Would it be possible to use .010" ABS instead? Then you can skip the painting altogether. McMaster-Carr caries it.

Mike Null
09-08-2012, 9:34 AM
This company says they have black film. Don't know the thickness.

http://www.tekra.com/tech_resources/general_lit/Polycarbonate_Films.pdf