The cure kinetics and activation energy (Ea) of bismaleimide homopolymer and modified bismaleimide resin systems with different chain extenders were investigated. The bismaleimide resin under investigation was bismaleimidodiphenyl methane (BMPM) and the chain extenders were (i) O-O′ diallyl bisphenol A (DABA) and (ii) methylenedianiline (MDA). Dynamic multiheating DSC method was used to study the kinetics of the curing process. Activation energies were determined for both unmodified and modified resins from nonisothermal multiheating rate DSC tests by using Ozawa and Kissinger models. Activation energy for BMPM homopolymer increased from 95？kJ/mol to 125？kJ/mol as a function of conversion. For the MDA-modified system the activation energy was independent of percentage conversion, at 108？kJ/mol. In the case of DABA-modified bismaleimide the activation energy increased steadily at 6？kJ/mol from 10 to 100% conversion. 1. Introduction High performance thermosets are of great interest as matrix resin for composites. Bismaleimide- (BMI-) and Polyimide- (PI-) based systems are among the more thermally stable thermosetting resins that are fast replacing the widely used epoxy resins. The unique properties of BMI resins, such as low moisture absorption, high crosslink density, good chemical resistance, and high glass transition temperature (Tg) make these resins suitable for prepregs, adhesives, electrical packaging, and other composite applications [1–3]. The properties they exhibit are directly related to the microstructure, with high cross-linking density, inherent aromatic structure and rigid molecular network. However, these microstructural characteristics results in inherent brittleness of the material. Extensive research is being done to enhance the toughness of BMIs by reducing the crosslink density, methods include the addition of reactive elastomers, copolymerization with allyl terminated copolymer, eutectic mixtures and modification with thermoplastics, or a combination of these methods [4]. According to the principles of molecular design, introducing a flexible linkage or chains into BMI can effectively improve the toughness of the resin [5], and the most preferred method for BMI resin modification is the copolymerization with allyl functional compounds and Michel addition chain reactions with aromatic diamines. The modified BMI resins can easily replace Epoderstand and predict the cure bxy resins, since the processing conditions are similar, but with superior performance characteristics. The properties of these BMI resin systems depend on the
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