CURE KINETICS OF ELEMENTARY REACTIONS OF A DIGLYCIDYL ETHER OF BISPHENOL-A DIAMINODIPHENYLSULFONE EPOXY-RESIN .2. CONVERSION VERSUS TIME

The kinetics of the elementary reactions (primary amine-epoxy and seco ndary amine-epoxy) in addition to the overall reaction have been studi ed in a diglycidyl ether of bisphenol A (DGEBA) epoxy resin system, cu red with diaminodiphenylsulfone (DDS) hardener. The conversion versus time data for the elementary reactions and for the overall reaction we re obtained by monitoring the changes in concentration of epoxy, prima ry and secondary amine groups during cure using near-infra-red spectro scopy. The data were evaluated using nth-order and autocatalytic kinet ic models. The primary amine-epoxy reaction (linear polymerization) wa s described well by the nth-order kinetic model over the whole range o f conversion of the primary amine, whereas the secondary amine-epoxy r eaction was described by both the nth-order kinetic and first-order au tocatalytic models in the ranges of initial 30% conversion at 130-degr ees-C cure, and 80% conversion at 205-degrees-C cure. The kinetic para meters for each reaction were also obtained. The reactivity ratio of t he secondary amine to the primary amine for a non-catalysed reaction i ncreased with increasing cure temperature, whereas the opposite trend was observed for the autocatalysed reaction.