Depending on the various polymer types involved, the treatment of plastic surfaces serves many functions.
decontamination
Anything that interferes with the contact between the coating film and the plastic needs to be removed.
Processing oils, dirt and grime, waxes, mold release agents and poorly retained plasticizers all need to be removed.
Surface Roughness Control
No surface is perfectly smooth, and various techniques enable the coater to match the coating on the plastic component to the coating viscosity to improve the adhesion of the film.
Surface to Adhesive Matching
Transformation of the outer surface of the plastic can provide an interface that is more similar or compatible with the chemical structure of the coating.
provide boundary layer
Plating or coating a surface with a primer often provides a more suitable surface for coating adhesion.
Control Oxide Formation
Polymers generally exhibit good oxidation resistance, but several methods promote oxide formation due to higher levels of surface activity on oxidized surfaces.
Absorbed Water Control
Many plastics readily absorb moisture from the surrounding atmosphere. This moisture can interfere with film adhesion, especially for coatings that require heat curing cycles.
