Characterization of the cure reactions of bismaleimide composite matrices

The cure reactions of 4,4'-bismaleimidodiphenyl methane (BMPM)/O, O'-diallyl bisphenol A (DABPA) bismaleimide composite matrices are characterized by systematic Fourier transform infra-red spectroscopy and differential scanning calorimetry studies as a function of isothermal exposures from 130 to 300 degrees C for time periods from 1 to 14h. The BMPM and DABPA monomers initially react to form an 'ene' adduct. The allyl, propenyl and maleimide double C=C bonds of the 'ene' adduct are completely reacted after 3 h at 250 degrees C. These cure reactions of the 'ene' molecule can initiate intra- or inter-molecularly and, hence, the cure path sequence is dependent on viscosity-time-temperature cure conditions. However, only 50% of the hydroxyl groups of the 'ene' adduct that form ether crosslinks via dehydration are reacted at 250 degrees C, over 10(4) h time periods, resulting in T-g increases and mechanical property deterioration. The degree of cure, al, as determined from d.s.c. measurements is less sensitive to the dehydration reaction because of a lower heal of reaction compared to the double C=C bond cure reactions. Additional BMI cure induced T-g increases in future aerospace service environments are discussed. (C) 1997 Elsevier Science Ltd.