Analysis of the curing behavior of bismaleimide resins

The curing behavior of bismaleimide resins was investigated using formulations containing different stoichiometric ratios of 1,1′‐(methylenedi‐4,1‐phenylene) bismaleimide (BMI) and 4,4′‐methylenedianiline (MDA). The resin cure involved a low temperature primary amine addition to the maleimide double bounds and a high temperature homopolymerization of the maleimide double bonds. The kinetics of the amine addition and the homopolymerization reactions were determined using Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry. The nucleophilic addition of the primary amines to the maleimide double bonds occurred by a second‐order reaction, and was at least two orders of magnitude faster than the homopolymerization reaction, which occurred by a multistep mechanism involving thermal initiation of chain growth, followed by chain propagation. A kinetic model for the curing behavior was developed and used to predict the extents of the amine addition and the homopolymerization reactions in networks cured under isothermal or dynamic conditions.