Painting ABS Plastic

Question:

We have found your site extremely useful for people engaged in painting in the smaller industrial sector. In my plant, we are painting components made out of ABS polymer both black and natural. We are facing a peculiar paint adhesion problem.

The adhesion is much better to the components made of natural ABS, as compared to black material. We use a solvent-based primer system and components are washed with isopropyl alcohol before painting. On the natural, there is no problem with adhesion whereas on the black, paint is peeling off. We have a normal rejection rate level of 5-10% in painting and repainting is absolutely required. Can you guide us? M. Y.

Answer:

Your problem could be due to the innate perversity of inanimate objects, or some sort of para psychological phenomenon. Simply stated, I am not sure what is going on. However, whatever is used to make the black ABS black could be migrating to the surface and acting as an interference coating thereby causing adhesion problems. Another possible cause is a surface contaminant on the ABS surfaces as it comes from the supplier or suppliers.

Furthermore, you are washing with isopropyl alcohol, which would not be my choice as a degreasing solvent or cleaning solvent for release agent removal because of its rapid evaporation rate. That is, it evaporates before the soil can be removed, leaving the soil on the part. You should consider using a slower-evaporating solvent such as mineral spirits.

One way to solve the problem, if you can afford it, is to conduct a surface analysis to determine differences between the natural and black ABS. Otherwise, ask your suppliers what is on the surface as supplied and the best removal procedure.