SURFACE MODIFICATION OF PTFE BY MICROWAVE PLASMA DOWNSTREAM TREATMENTTO IMPROVE ADHESION WITH AN EPOXY MATRIX

Due to their high thermal stability, PTFE fibres are more interesting than PE fibres but their low surface energy presents considerable inte rfacial problems in creating polymer/polymer composites. Thus a variet y of treatments have been applied in order to activate PTFE surfaces a nd to promote adhesion. Chemical treatments have been widely used but, in that case the depth of the modification is not well controlled. Si nce few years, gas plasma techniques and especially radio frequency pl asma techniques have been used to activate the surface of numerous pol ymers and some studies show that they are attractive for PTFE. Only fe w studies are concerned with PTFE surfaces modified by microwave plasm a treatments in the literature. Thus the aim of this work is to study the surface modification of PTFE by a microwave plasma downstream trea tment. The influence of various processing parameters (power, gas flow , plasma exposure time) is evaluated for two gases : H-2 and NH3. The wetting behavior and the chemical modifications identified by XPS are discussed as a function of the gas nature and of the processing condit ions. The evolutions of the polar and dispersive components of the sur face energy are related to the defluorination rate and, depending on t he gas used to the new species created by the microwave plasma treatme nt. The results obtained by XPS and by the contact angle measurements let us explain the evolution of the interfacial properties of a single fibre composite determined by the microbond test.