Sequential interpenetrating polymer networks from bisphenol A based cyanate ester and bimaleimide: Properties of the neat resin and composites

Abstract

Blends of varying composition of a bisphenol A based cyanate ester—viz., 2,2-bis-(4-cyanatophenyl) propane (BACY)—and a bisphenol A based bismaleimide—viz., 2,2-bis[4-(4-maleimido phenoxy) phenyl] propane (BMIP)—were cured together in a sequential manner to derive bismaleimide–triazine network polymers. Enhancing the bismaleimide content was conducive for decreasing the tensile properties and improving both the flexural strength and fracture toughness of the cyanate ester-rich neat resin blends. Although DMA analyses of the cured blend indicated a homogeneous network for the cyanate ester dominated compositions, microphase separation occurred on enriching the blend with the bismaleimide. Addition of bismaleimide did not result in any enhancement in Tg of the blend. Interlinking of the two networks and enhancing crosslink density through coreaction with 4-cyanatophenyl maleimide impaired both the mechanical and fracture properties of the interpenetrating polymer network (IPN), although the Tg showed an improvement. Presence of the bismaleimide was conducive for enhancing the mechanical properties of the composites of the cyanate ester rich blend, whereas a higher concentration of it led to poorer mechanical properties due to the formation of a brittle interphase. The IPNs showed reduced moisture absorption and low dielectric constant and dissipation factor, the latter properties being independent of the blend composition. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2737–2746, 1999