Analysis of the kinetics and mechanism of the cure of a bismaleimide-diamine thermoset

The polymerisation kinetics of 1,1'-(methylenedi-1,4-phenylene)bismaleimide (MDP-BMI) with the aromatic diamine 1,1'-diaminodiphenylmethane (DDM) has been investigated. Fourier-transform near infrared (FT-NIR) spectroscopy wa s used to obtain quantitative data for the various functional groups in BMI /DDM mixtures with respect to time during isothermal cure over the temperat ure range 160-180 degrees C. Quantitative rate data were obtained for all t he functional groups in the resins by mathematical differentiation of the t ime dependence of the concentrations. A mechanism for the polymerisation ha s been deduced from this rate data, in which the rate-determining step was found to involve a reaction between the primary or secondary amine and a hy drogen bonded complex formed between the maleimide and amine groups. The ra re coefficients for the reaction of the amines with the complex were found to be four times larger for the primary amine than that for the secondary a mine. The activation energy for the cure over this temperature range was fo und to be 43 kJ mol(-1). (C) 2000 Elsevier Science Ltd. All rights reserved .