Good paint for covering corrugated plastic polypropylene?
bradleyheathhays
| Posted in General Discussion on
I’m looking for a good paint I can put in a spray gun and sticks to polypropylene well. I’ve got a good number of those street signs made out of corrugated polypropylene and I’d like to cover with white and remake into new signs. I’ve been told the best cleaning treatment for this plastic would be to clean with 50/50 alcohol/water, sand with 80-100 grit, then wipe off again with the alcohol mixture. I’m open to more advice here if you have some.
Anyone aware of a paint sold by the gallon that sticks to polypropylene well? The cheaper the better of course.
Replies
There are adhesion promoting primers for going over plastics. 3m makes one. An automotive paint supplier would be the one to go see. Nothing is cheap!
Polypropylene and polyethylene are notoriously difficult to bond to, as you may be aware (and thus your question)--you'll find them called out as exceptions to most products that are advertised to stick to anything, even things targeted at plastics. There are some spray paints (Krylon etc) that are intended for plastics. A quick glance at the technical data sheet for the Rust Oleum plastic primer product specifically says it will bond to polypropylene.
You mentioned gallons--a bunch of rattle cans would be a bit of a drag, but if the alternative is automotive paint, you'll save money on the cans. I assume that most all plastic auto body parts will be ABS, which is much easier to bond to than polypropylene.
There are adhesion primers for general use--Bondz by Zinsser is one that I have used for covering over glossy paint without etching, etc. That one also specifically says it is not for use on polypropylene. Maybe auto primers are different. Most general use paints/primers that are for "plastic" are for PVC house trim.
Bottom line: even if it says "for use on most plastics" I would read all the fine print, and maybe even contact the manufacturer for specific guidance.
https://www.rustoleum.com/-/media/2209A33F94D145C2A1D557ED68D9E46C.ashx
https://www.amazon.com/Rust-Oleum-213517T-Specialty-Appliance-Plastic/dp/B0019K43WG
Most automobile plastics are polypropylene or polycarbonate ( bumpers, headlights mainly) and are painted or clear coated all the time. I had a primer for that, long gone, but I just remembered the name, it was called " Bulldog" and it probably was purchased at a NAPA store or maybe even at a actual automotive paint supplier. I know I've been to one a couple of times but I don't remember why. I remember the product worked but I don't know if it's the best available. The idea that you need to clean and remove contaminants is certainly true but with the stuff I used as a primer and the way it bonded I'm not sure that roughing the surface prior to use would be necessary. The stuff seemed to do that all on its own. The whole idea of a primer is that it is an interface between dissimilar materials. It sticks to something and permits something else to stick to it. With the proper primer you might have a wide choice as to the type of paint you topcoat with. I would think that the guys at the local auto body shop would know all about this! Automotive paints that I've purchased in a can( not rattle cans) seemed to be some kind of lacquer based paint that dries almost on contact. If your set up to spray then I would think purchasing rattle cans would be foolish!