CURE KINETICS OF DIFFERENT MOLAR RATIOS OF 4,4'/BISMALEIMIDODIPHENYLMETHANE AND BISPHENOL-A DICYANATE

Bismaleimide-triazine (BT) resins are thermosets derived from the addition polymerization of different molar ratios of 4,4'-bismaleimidodiphenylmethane (BM) and bisphenol A dicyanate (BA). The possible cross-linking reactions involved in the formation of BT resins are addition polymerization of BM, cyclotrimerization of BA, and heteropolymerization between BM and BA. Fourier-transform infrared spectroscopy reveals that cyclotrimerization of BA occurs during the cure of a 1 : 2 molar ratio of BM to BA (as 1M2A). No sign of cyclotrimerization is observed for the case of the 1 : 1 molar ratio of BM to BA (as 1M1A). A dynamic differential scanning calorimeter (DSC) is employed to study the cure kinetics. The apparent activation energy evaluated from the Prime method is increased with the content of the BM component in the starting mixture. The different pattern of activation energy with fractional conversion (a) indicates the different chemical nature for the cure reactions of 1M1A and 1M2A. The empirical rate functions thus evaluated are 2.32 X 10(5) + 5.62 X 10(5)alpha - 8.61 X 10(5)alpha2 and 6.07 X 10(5) + 1.06 X 10(6)alpha - 1.66 X 10(6)alpha2 s-1 for the cure reactions of 1M1A and 1M2A, respectively. (C) 1994 John Wiley & Sons, Inc.