Ask the Expert Question-and-Answer Archive

by Ron Joseph

March, 2005

Paint Coating Peeling from Plastic

Q. Currently, we are suffering from the paint peel issue. As I know, there are many factors which could lead to the paint peel-off, such as low surface energy of plastics, contamination of plastics surface, insufficient curing, etc.

In the past few days, we have been conducting a series of tests to simulate the conditions in order to find the potential reasons. Unfortunately, no paint peel re-occur even if we tried so many times.

For your information, only few pieces were rejected from customers instead of the whole lot.

Is it due to our potential failure in our process control? We didn't well-control the 1st layer before spraying the 2nd layer? Is it possible that potential failure could occur after mass production is finished?

A. The most common cause of paint peeling (or delamination) is due to inadequate surface preparation. In the case of plastics, you also need to consider the surface tension of the plastic and the surface tension of the primer coating (1st layer).

The second most common reason for peeling is solvent entrapment. That means that the coating starts to set up before all the solvent can evaporate. Very often this occurs when the painter applies too much paint too soon. If you can smell solvent in the paint when you peel it from the plastic, then in all probability this is the cause of the problem.

Another possible cause is that the primer and topcoat are incompatible, but if that were the case you would have already seen numerous problems.

I hope this gives you a good starting point to solve your problem.

Best Wishes,

Ron Joseph