Use of X-Ray Photoelectron Spectroscopy to Study the Failure of an Adhesive Joint Between Two Polymers

The interface of the Kynar®-Nylon adhesive joint was examined by X-ray photoelectron spectroscopy. It was found that the failure was neither adhesive nor cohesive. XPS results indicated that the fracture path occurred through a weak boundary layer which migrated to the interface possibly during the bonding process. The weak boundary layer consists of molecules which have -(CH₂)_n and (CF₂)_n structural units which are probably present as low molecular weight impurities formed during the polymerization of vinylidene fluoride or subsurface contaminants in the samples. This work presents the first conclusive evidence that confirms the existence of a weak boundary layer in an adhesive joint.