Influence of low-pressure plasma treatment on adhesive bonding between polybutylene terephthalat (PBT) and aluminum

Adhesive joints between polybutylene terephthalat (PBT) and aluminum with epoxy (EP) and polyurethane (PU) resins have been tested after surface treatment by low-pressure plasma. By this means the adhesive bonding strength increased slightly in case of PU adhesive, but 3.5-10 times in case of EP adhesive. In accordance the fracture turns from an adhesive failure to a fracture predominantly in the plastic part. Freshly injected surfaces showed high adhesive strength with EP adhesive as compared with unfreshly injected ones. The increase of joining strength can be attributed to a corresponding increase of the PBT surface tension.