Cure reaction for modified diallylbisphenol A/diaminodiphenylsulfone/bismaleimide

The glass-transition temperature as a function of curing conversion for a modified diallylbisphenol A/diaminodiphenylsulfone/bismaleimide (BMI) resin was investigated at different temperature regimes and modeled using a modified Di Benedetto equation. Although the relationship between the glass-transition temperature and conversion of the BMI system conforms to the Di Benedetto equation for alpha < 0.6 and at lower cure temperatures, at higher cure temperatures the results deviated significantly from the equation; thus, it was an inadequate model for the system. Fourier transform IR analysis showed that the major crosslinking reactions did not occur during cure for the modified BMI at and below 150degreesC. However, as the cure temperature was increased, the crosslinking reactions responsible for 3-dimensional network structures became more dominant. At 190degreesC the C-N-C-stretch vibration of the uncured maleimide ring converted into succinimide rings in the curing process. Simultaneously, a decrease was observed for the absorbance bands of ==C-H-bending (maleimide). The higher cure temperatures induced a significantly faster initial crosslinking rate and also resulted in a shorter period of time after which further crosslinking was retarded, because the increase in the crosslinks also physically slowed further crosslinking activity. (C) 2002 Wiley Periodicals, Inc.