Ask the Expert Question-and-Answer Archive

by Ron Joseph

July, 2003

Painting Polyolefins

Q. I am trying to find a source or process which will enable me to coat or paint materials that we rotationally mold. In particular, I'm trying to get a real high luster finish. We generally work in Polyolefins (HD Poly, LD Poly).

A. I referred your question to Gary Gbur of Sherwin-Williams who heads the plastics coatings group. He has kindly given the following response:

Polyolefin plastics are a difficult challenge for paint adhesion. Waterborne and solvent borne coatings which have been formulated for engineered plastics such as polycarbonate , ABS, and polystyrene, usually have adhesion problems with polyethylene and polypropylene substrates. There are adhesion promoting additives which may work in specific paint systems, but these usually result in a compromise of paint properties such as chemical resistance or hardness. The best suggestion for improving the adhesion to polyolefins is to flame treat the plastic surface. Corona plasma is another recommended surface treatment to promote coating adhesion. .