Surface modification of polytetrafluoroethylene films via graft copolymerization for auto-adhesion

Abstract

The surfaces of Ar plasma-pretreated polytetrafluoroethylene (PTFE) films are further functionalized via UV-induced graft copolymerization with amphoteric N,.N′-dimethyl(methacryloylethyl)ammonium propansulfonate (DMAPS) either in Ar atmosphere, or under atmospheric conditions and in the absence of a polymerization initiator. The so-modified PTFE films from either process are capable of exhibiting adhesive-free adhesion or auto-adhesion with one another when brought into intimate contact in the presence of a small quantity of water. The lap shear adhesion strength increases with increasing graft concentration and can readily exceed the yield strength of the PTFE substrate. Two plasma-pretreated PTFE films also readily undergo thermal graft copolymerization with concurrent lamination when lapped together in the presence of a small quantity of the DMAPS monomer solution at elevated temperature in the atmosphere. The surface compositions of the graft-copolymerized PTFE films and the delaminated surfaces were characterized by X-ray photoelectron spectroscopy (XPS). In most cases, adhesional failure occurred near the graft-substrate interphase. © 1998 John Wiley & Sons, Inc.