Painting Polypropylene Type Plastic?

beavercreek

beavercreek

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I am going to build an oiling stage along the lines of the one at Chama and am going to use the toy straw stuff that comes with many joiners as well as the tougher plastic straw sections.

The problem will be getting a paint that will adhere to the 'joiner' sections as they are made of a polypropylene type of plastic.
I can remember some time back, on the forum, that someone had some good advice on how to prepare the plastic so that the final coats would not 'flake' off after a period of time.

Tried car primer on the same type of plastic and it eventually started to flake off as the plastic went through the rigours of being out side.

These are the type of straw things

straw pipes.jpg


and this is the oil stage at Chama that I hope to 'emulate'

chama oil rack.jpg
 
I have to ask Beav, was the primer you used a, for 'plastic' body parts, primer. Ordinary car primer certainly wouldn't hold well, it's too brittle. There are many parts of modern cars now made of all sorts of different plastics, Polyprop is one, as is ABS.
 
Halfords do a primer for plastic car-parts (bumpers and the like), that seems to be flexible enough to cope with thermal expansion and adheres quite well..

Main thing with plastics (I find) is that you need to degrease the softer, more pliable types well. If you can key the surface, it helps.. I have had some success with so-called 'liquid sander', but results can be variable. - Test a small area first! AND try your paint on top of a test-piece.
 
G-force1 said:
I have to ask Beav, was the primer you used a, for 'plastic' body parts, primer. Ordinary car primer certainly wouldn't hold well, it's too brittle. There are many parts of modern cars now made of all sorts of different plastics, Polyprop is one, as is ABS.
Click to expand...

It was for plastic body parts ie bumpers, aerofoils etc.
 
PhilP said:
Halfords do a primer for plastic car-parts (bumpers and the like), that seems to be flexible enough to cope with thermal expansion and adheres quite well..

Main thing with plastics (I find) is that you need to degrease the softer, more pliable types well. If you can key the surface, it helps.. I have had some success with so-called 'liquid sander', but results can be variable. - Test a small area first! AND try your paint on top of a test-piece.
Click to expand...

Hi Phil
Tried the Halfords plastic primer type stuff, as mentioned in first post, and it eventually flaked off.
Where can you get the 'liquid sander' from and what is its name?
 
beavercreek said:
Hi Phil
Tried the Halfords plastic primer type stuff, as mentioned in first post, and it eventually flaked off.
Where can you get the 'liquid sander' from and what is its name?
Click to expand...

Literally that, 'Liquid Sander'.. Any of the DIY sheds. - it is really designed for gloss house paint, but it seems to 'matt' the surface of some plastics.
IMHO, expecting anything to stick, and cope with the vagaries of our climate, is asking a lot..

I agree, once you attack a car with any of these products, they do not last.. I wonder if the manufacturers (possible body-shops too) use a two-pack product for this??

<edit>
Mine came from Wickes, many years ago..
A quick Google, shows it available from Wickes and B&Q..
 
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Does sound like a keying problem if you had the right primer. Small parts are always a pain.

Another option might be to speak to a local Auto paint supplier.
 
G-force1 said:
I have to ask Beav, was the primer you used a, for 'plastic' body parts, primer. Ordinary car primer certainly wouldn't hold well, it's too brittle. There are many parts of modern cars now made of all sorts of different plastics, Polyprop is one, as is ABS.
Click to expand...

Never found the need on the railway, but in the model boating hobby, both wet and with rapidly changing air temperatures, we always used to use a thin but complete coat of two part liquid fibreglass resin directly over the soft poly based structures and pipe work. This was then coated with decent red (possibly Plasticoat) primer and finishing with a (usually) Plasticoat spray or brushed coat. It was rock hard when fully cured and solved two problems by making the pipe work much stronger and with no peeling finish etc. Just checked a highly detailed and well used boat (tanker, British Corporal) built in 1998 which is completely intact and undamaged.
 
I made plenty of model boats, but never came across that idea . . . it was a bit before 1998 though.

I like, sounds a good 'un. The only drawback I can think of might be a slight loss of detail, but careful application should take care of most of that.
 
I have painted many plastic/metal/ wood items that stay out all year around and have not had any peeling/flaking problems except with the polypropylene type plastics.

Thanks for the advice lads.... I will try the solutions and post back on how they turn out
 
Possibly a little drastic and not suitable for such small parts but stick with it........
But it goes some way to pointing up the causes of the problems of painting PP. And giving a few clues to fixing them. But is anything a real long term fix. The Rustoleum product sounds interesting. Max
 
Max...... I can see my liitle parts(?) disappearing into a blob if I get the flamethrower out!....but a very good demonstration for larger projects...good post

Mick.....good find!, although I am not sure it will be any better than the Halfords stuff....I will it though after a bit of work with alchohol and wire wool
 
I've not used it, but the thin 'brushing' epoxy used when building kayaks might work. Epoxy seems to stick to virtually anything, after all...

Search 'roll and tip epoxy'.
 
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