Lamination of polytetrafluoroethylene films via surface thermal graft copolymerization with ionic and zwitterionic monomers

Abstract

Surface thermal graft copolymerization with concurrent lamination was carried out between two argon plasma-pretreated polytetrafluoroethylene (PTFE) films in the presence of aqueous zwitterionic solutions of N,N-dimethyl-N-methacrylamidopropyl-N-(3-sulfopropyl)ammonium betain (DMASAB), N,N-dimethyl(methacryloylethyl)ammonium propansulfonate (DMAPS), and 1-(3-sulfopropyl)-2-vinylpyridinium betaine (SVPB), as well as an aqueous ionic solution of potassium-2-sulfopropylacrylate (SPA) and potassium-2-sulfopropyl methacrylate (SPM), under atmospheric conditions and in the complete absence of an added initiator and system degassing. The lap shear adhesion strength between the PTFE films from simultaneous grafting and lamination depended on the argon plasma pretreatment time of PTFE films, the thermal lamination temperature, the concentration of the monomer solution, and the ionic nature of the grafted chains. Lap shear adhesion strength greater than 120 N/cm2 and exceeding the yield strength of the PTFE substrate used could be readily obtained in most PTFE/zwitterion/PTFE assemblies after simultaneous thermal graft copolymerization and lamination. The chemical compositions of the graft-copolymerized surfaces were studied by X-ray photoelectron spectroscopy (XPS).