IMPROVING ADHESION IN INTERLEAF COMPOSITES USING PLASMA PROCESSING

A novel radio frequency (RF) plasma processing technique, known as pla sma induced polymerization (PIP), was used in a multistep plasma proce ss to deposit a thin, uniform layer of viscoelastic material on Upilex -S high-temperature polyimide film in order to enhance adhesion betwee n the film and the resin in carbon fiber interleaf composites using ep oxy (Hercules 8551-7A) resin systems. In a three-phase study, the proc essing parameters of residence time, plasma power, plasma pressure, an d monomer gas were varied to investigate adhesion improvement. Deposit ions were characterized using scanning electron microscopy and X-ray p hotoelectron spectroscopy (XPS) analysis. Compressive mode II strain e nergy release rate (G(IIc)) was characterized by end-notched flexure t esting to rank and predict the best RF process for a thermoplastic fil m interleaf composite structure using polyimide film. Adhesion was imp roved by as much as 140% over the adhesive performance of untreated Up ilex-S using the epoxy resin system. However, adhesive performance was improved in the relatively low temperature (177 degrees C) processing system, and this plasma deposition may not be stable at the higher pr ocessing temperatures needed for processing polyimide matrix systems s uch as PMR-15. (C) 1995 John Wiley and Sons, Inc.