Enhanced Adhesive Performance of Thermoplastic Poly(imide-siloxane) Segmented Copolymer with PEEK®-Graphite Composites by Gas Plasma Treatment

Abstract

The adhesive bond performance of PEEK®-graphite composites (APC-2/AS4) with melt fabricated films derived from either a novel thermoplastic poly(imide-30 wt% siloxane) segmented copolymer or commercial thermoplastic polyetherimide (Ultem® 1000), has been studied as a function of surface modifications. The latter included grit blasting and gas plasma etching treatments with oxygen, ammonia, nitrogen and argon. Adhesive bond strength was evaluated with single lap shear samples (SLSS) which were prepared from PEEKl-graphite composite adherends and compression molded thermoplastic poly(imide-30 wt% siloxane) segmented copolymer film adhesives. Greatly improved single lap shear strength values were obtained by several gas plasma treatments as well as by grit blasting. For example, SLSS values were increased from less than 1000 psi to approximately 5000 psi. The morphological and chemical changes of PEEKS-graphite composites with surface treatment were investigated by scanning electron microscopy (SEM), contact angle measurement and X-ray photoelectron spectroscopy (XPS). The results suggest that the improved adhesive bond strength produced by the gas plasma treatments was a function of the interaction of derived surface acidic functional group(s) with the 'basic' polyimide adhesives.