Painting plastics can be simple and successful or it can be complex and a disaster. The reason for this is that “plastics” include a wide number of organic resin formulations and a wide range of processing methods. On molded products, mold release items (silicone’s, waxes and surface active agents) can cause adhesion problems. Some mold release items are paintable, but others will keep the coating from adhering. The best advice: follow the directions for painting the specific product from the manufacture. Often the plastic has a factory applied primer or finish coat. This simplifies the problem, as you are now painting paint and not the plastic, so proceed with normal good painting practice, either interior or exterior.

  If the manufacture advice in not available and the object has not been factory primed-what next? Oil, powder, dust or almost any contaminate can adversely affect adhesion of paint. Paint adheres better to roughened surfaces than smooth surfaces. Certain proprietary primers are touted for good adhesion to plastics. An acceptable procedure would be:

1. Wipe the surface with a cleaning solvent. The cleaner must be compatible with the plastic, as the wrong solvent can be damaging. Sometimes scrubbing with soap and water is an alternative. Try a sample in a inconspicuous location and observe results. (Avoid solvents that cause crazing, cracking or dissolve the plastic).

2.  Sanding with “wet or dry” abrasive does a good job of removing the gloss or roughing dense surfaces. This often removes “mold release agents” and gives paint a chance to adhere. This can be done in conjunction with detergent or solvent. Rinse well after sanding to remove dust or residue. Let dry.

3.  Depending on the type of exposure, apply a primer (some clear, some pigmented) that is recommended for adhesion to plastics or hard to coat surfaces.

4.  Finish with appropriate finish coat.

A sample should be prepared before doing the entire job.