Priming plastic

[Nanako]

Hello all, i did recently paint a windowframe, which is made of plastic. I knew that paint would never stick to smooth shiny plastic, so i went and got some special primer for it

This stuff is a thick grey paste, and i know from my warhammer days, it smells exactly like the Plastic Cement i used to assemble models back then. I'm sure it's a similar kind of substance, being highly corrosive and primarily working by partially melting the plastic

Anyways this process went well, overall, once primed the surface took paint easily, and now the windowframe looks wonderful. But there were a few hiccups in the process. And now i find myself on the eve of repeating it all for a different windowframe, i'm wondering if theres anything i can do to refine it:

1. How thick is primer supposed to be spread? I tried to play it safe and went for total coverage, every millimetre of plastic was covered in a smooth grey, not a bit of the white underneath remained. But this came at the cost of using 75% of the tin on that one windowframe (i got two tins so im good for the next job). I cant help wondering if i went overboard, and spreading it thinner might have been fine

2. The corrosiion is a bit of a problem, i used a small foam roller, 4 inch length, and by the end of the process, this stuff had just devoured the roller, it fell off and was forevermore unuseable. Maybe theyre meant to be consumable anyways, but i'm thinking foam isnt the best material, is there something more suitable?

any other insights on priming plastic are welcome

 

[evdamadiynot]

I painted some really grotty 25yr old upvc windows for a relative.
I masked the glass and surrounding paintwork and used plastic primer aerosol from Halfords followed by car paint of their colour choice which was gloss black.
Looked amazing and was tougher than I ever imagined.

Nine months later the housing association contractor arrived and replaced the whole lot.

 

[Scally-Ho]

I used Jenolite plastic primer spray followed by two careful coats of auto spray finish. That was 7 or so years ago and it's still as good as new on a previously white plastic rear door. A regular wipe with a damp cloth keeps it looking good

 

[foxhole]

You can spray directly with correct plastics paint no primer required.
Did mine with rattle cans around one can per window.

 

[justigator]

Dulux Weathershield Multisurface is explicitly sold as suitable for uPVC. I've only ever used it on wood myself.

 

[evdamadiynot]

Interesting idea but crikey you wouldn't want to waste a drop at that price!!!

 

[JohnD]

I have had excellent results painting hard plastics with an oil-based non-drip gloss paint.

No primer, no undercoat, a single flowing coat.

Get it thoroughly clean first and remove any surface erosion with white spirit and wire wool. I expect fine wet and dry would also do.

I don't know how long it lasts, but I have a meter box and some waste pipes I did 30 years ago. The pipes are getting a bit dull. Some indoor plastic remains glossy.

 

[jj4091]

You can spray directly with correct plastics paint no primer required.
Did mine with rattle cans around one can per window.

Were they white to start with. A very impressive job. which paint makers did you use if you don't mind me asking. May be needing it myself soon.

 

[foxhole]

Were they white to start with. A very impressive job. which paint makers did you use if you don't mind me asking. May be needing it myself soon.

Yes white to black , used paint from PN-trade ( my link was removed).
They do matching paint in small tins to touch up any areas too small or difficult to spray .