High-performance bismaleimide matrices: Cure kinetics and mechanism

Kinetics and mechanism of equifunctional 4,4'-(N,N'-bismaleimide)-diphenylmethane/2,2'-diallyl-bisphenol A (BMDM/DABPA) and model (phenylmaleimide/2,2'-diallylphenol) (PMI/AP) systems have been studied in the temperature range 140-400degreesC using IR-, H-1- and C-13-NMR spectroscopy, gas chromatography-mass spectrometry GCMS), differential scanning calorimetry (DSC) and isothermal calorimetry. It was established that the cure mechanism consists a unique combination of step-wise and chain polymerization and polycondensation reactions: step-wise ene addition reaction of allyl group to maleimide one and consecutive/parallel chain polymerization of maleimide and propenyl groups generated by first reaction. The latter reaction is the main crosslinking reaction. The second source of crosslinking is a dehydration reaction of phenol groups that proceeds with mandatory participation as one of the component 1:1 adduct (product of step-wise polymerization). Homopolymerization of maleimide groups proceeds autocatalytically under the action of free radicals generated by thermal decomposition of maleimide-propenyl groups' donor-acceptor pairs. Steric hindrance in 2,2'-diallyl-bisphenol A prevents the reversible Diels-Alder reaction but this reaction proceeds in model systems. Some thermodynamic and kinetic parameters of the reactions are determined. Copyright (C) 2003 John Wiley Sons, Ltd.