Abstract
Poly(butylene terephthalate) (PBT) , which is a typical engineering plastic, has been widely used for electrical components and also automobile parts due to its heat resistance and dimensional stability. In general, PBT should be annealed to obtain high dimensional stability at a temperature above the glass transition temperature prior to practical use. In this study, influence of annealing treatment on adhesion behavior of PBT with epoxy adhesive was studied. The tensile adhesion strength decreased after the annealing treatment of PBT. In the case of the untreated PBT, the failure depth after the failure was nearly 0nm. Once the PBT was annealed, the average failure depth became 4 nm. The above results imply that the failure mechanism for the system transformed from interfacial failure to cohesive fracture upon annealing treatment. This can be easily understood by taking into account that a mechanically weak layer is formed in the surface region of PBT after the annealing. Presence of such a weak boundary layer was evaluated by grazing incidence X-ray diffraction measurement and by scanning viscoelasticity microscopy. Improvement of adhesive property was attained by surface treatment.
