Amorphous Bisphenol A Based Poly(Arylene Ether) Modified Cyanate Ester Networks

Abstract

Cyanate ester or triazine networks are receiving considerable attention as potential candidates for high-temperature adhesives and composite matrices. Low toughness is a major drawback with most cross linked thermosetting materials, including the cyanate ester networks. Considerable attention has been devoted to the aspect of toughening such brittle networks in our laboratories. Reactive functional thermoplastic toughness modifiers not only enhance toughness but also permit highly desirable stability to solvent stress cracking without seriously affecting the moderately high modulus. We have earlier reported on various aspects of this technology as applied to epoxy and bismaleimide systems. Careful control of the hetetophase morphological structure is necessary to achieve significant toughening. In the present work, we have focused on modifications of a specific cyanate ester network system based on bisphenol-A with thermoplastic modifiers of varying backbone molecular weight and chemistry. In particular, hydroxyl or cyanato functional bispheno]-A based amorphous poly(arylene ether sulfone)s and poly(arylene ether ketone)s have been successfully utilized. Blends of reactive and non-reactive polysulfones were also demonstrated to be useful tougheners, apparently by allowing phase size control. The use of polyarylene ether ketones (which are of lower polarity than the polyarylene ether sulfones) resulted in larger, well defined morphologies, which in turn afforded tougher networks. It was demonstrated that either hydroxyl or cyanato reactive end groups could be effectively utilized. Both were superior to non-reactive systems in terms of both mechanical performance and solvent stability..