How to spray plastic car bumpers

Its not an isolator you need but a plastic adhesive promoting primer available from paint mixing outlets.

You've not got a reaction just an adhesive problem, hence the need of a promoting primer.

Stephen.

No reaction at all, the problem is the plastic is not 'keyed', you need a special plastic primer.

You need a special primer. Halfords sell it. But I'm not sure the one type does all types of plastic.

I have plastic covers on screw heads on my SD1 - loads of them. In two shades of grey. They are the same shape and size as the type used on kitchen units etc, but those are only easily available in white black brown and beige. So I sprayed some. Had several attempts to find a good primer - the best one being a clear one from Loctite, Plastic Padding Acryplas plastics primer. It seems to work well on other flexible plastics too. Says not suitable for polythene or soft PVC.

As Others have said, you must use the right plastic primer.

I always mix some plasticiser in with the top coat and laquer too (if used) (10-15%) as that will crack / peel / craze too if its too hard (plastic bumpers flex, contract and expand alot more than you think)

Tim..

Here's the procedure for spraying a plastic bumper. I know, because I've done it and I've made the stupid mistakes:

1) Panel wipe the whole bumper to remove as much mould release agent as possible. 2) Thoroughly scotchbrite the area to be painted, using a grey (1200 grit equiv) and plenty of panel wipe 3) Do not attack the area to be painted with DA sander like I did. There's no need, and it's very difficult to sand plastic - it tends to form little beads of plastic rather than sand evenly. 4) Mask the area not to be painted. Use 3M fineline tape for the edge between painted and unpainted to get a decent line. PANEL WIPE AGAIN, just before spraying. 5) Spray plastic primer - it's available in 1K form to go through a spraygun, and is very thin - expect as little fault covering power as you would from a top coat - IIRC U-pol sell most of their paints as rattle cans if you don't have a gun, and it's called "Adhesion Promoter" IIRC. 6) Let the plastic primer flash off - mix your topcoat or get shaking those rattle cans. 7) Spray top coat (I'm going to assume you know how to spray).

8) Remove masking once the paint has flashed off. It's not hard to tell when the paint is set enough to not get everywhere when you unmask and not set so much it'll flake. About 10 or 15 minutes for 2 pack IME.

That's the proper way to spray a plastic bumper. Leave mould release agent on there or use the wrong primer and you can't expect it to last.

If there is a flex additive available for the paint system you're using, use it, as it'll help reduce stone chips by a hell of a lot.

When was the last time you actually was involved with modern day paint finishes Stephen? Because I can tell you that you are indeed talking cak.

I would have said very recently, unlike you moron, never mind the other four people who say the same as Stephen. Now f*ck off troll.

Pray tell which part of his post is 'cak'?

Seems pretty accurate to me.

I was puzzled there for a nanosecond until I realised you're just a troll.

I've probably forgotten more than you will ever know about painting and as I can't find any meaningful contribution from you on any group that I subscribe to comfirms it.

Indeed, I may be guilty of a somewhat short answer to the OP's question whereas Doki gave a very descriptive and lengthy one.

Stephen.

If you check out the trolls other postings you'll find them all negative without an ounce of positive contribution.

Stephen.

So what do you advocate for the correct procedure to rectify the problem.

r

Check the headers, the clue is in the false addresses used. Just killfile the tw*t. It's not the Conor we all know and love ;-)

Well yes, but two people's parents can misspell the same name? ;-)