Thermal graft copolymerization with concurrent lamination of low density polyethylene and poly(tetrafluoroethylene) films

Abstract

A simple technique of thermal graft copolymerization of glycidyl methacrylate (GMA) on argon plasma pretreated poly(tetrafluoroethylene) (PTFE) films or low density polyethylene (LDPE) films with simultaneous lamination of the two films was demonstrated. The effect of crosslinking agent on the adhesion strength of the PTFE/PTFE interface was also investigated. The simultaneous thermal grafting and lamination process was carried out under atmospheric conditions and in the complete absence of a polymerization initiator. The surface structure and composition of the graft copolymerized PTFE and LDPE films from either self-delamination in acetone or mechanical delamination were studied by X-ray photoelectron spectroscopy (XPS). The efficiency of surface graft copolymerization and lamination was found to be strongly dependent on the plasma pretreatment time of the substrate, graft concentration, thermal grafting/lamination temperature and time. T-peel adhesion strengths of about 0.9 and 1.7 N cm-1 were achieved for the PTFE/GMA/PTFE assemblies in the absence and presence, respectively, of the crosslinking agent, triallyl-1,3,5-benzenetricarboxylate (TBTC). The T-peel adhesion strength of the LDPE/GMA/LDPE assembly, on the other hand, can reach about 2.6 N cm-1 in the absence of TBTC. XPS analysis of the mechanically delaminated surfaces suggests that the failure mode of the PTFE/GMA/PTFE assembly and the PTFE/GMA+2 vol% TBTC/PTFE assembly is adhesional in nature, and that of the LDPE/GMA/LDPE assembly is cohesive.