Lamination of conductive polypyrrole films to poly(tetrafluoroethylene) films via interfacial graft copolymerization

Abstract

A simple technique for the lamination of a conductive polymer film to an inert dielectric polymer film was demonstrated. The electrochemically synthesized and p-toluenesulfonic acid-doped polypyrrole (PPY) film was laminated simultaneously to the argon plasma-pretreated PTFE film during the thermally induced graft copolymerization of the PTFE surface with a functional monomer. The graft copolymerization was carried out using glycidyl methacrylate (GMA) monomer containing 20% v/v hexamethyldiamine (HMDA) and in the absence of any polymerization initiator. Thermally induced graft copolymerization of the GMA monomer on the PPY surface was minimal. The lap shear and T-peel adhesion strengths of the laminates were found to be dependent on the GMA graft concentration on the PTFE surface, which, in turn, was affected by the plasma pretreatment time of the film. To increase the GMA graft concentration for the enhancement of adhesion strength, the plasma-pretreated PTFE surfaces were premodified via UV-induced graft copolymerization with GMA prior to the simultaneous thermal graft copolymerization and lamination process. The modified surfaces and interfaces were characterized by X-ray photoelectron spectroscopy (XPS). Through XPS measurements of the delaminated surfaces, it was found that the PPY/PTFE laminates failed predominantly by cohesive failure inside the PTFE substrate.