INFLUENCE OF THE REACTIVITY OF AMINE HYDROGENS AND THE EVAPORATION OFMONOMERS ON THE CURE KINETICS OF EPOXY-AMINE - KINETIC QUESTIONS

The mechanism of cure (pregel) of a highly purified diglycidylether of bisphenol A (DGEBA, 99.6% molecular weight = 340 g mol(-1)) with 1,3- bis(aminomethyl)-cyclohexane (1,3 BAC) was studied. A kinetic model wa s developed which considered the different reactivities of the amine h ydrogens involved in the process. The possibility of simultaneous evap oration of the starting monomers and its influence on the rate of reac tion is also taken into account. The rate constants of the elementary process and the general mechanism were determined. The ratio of the el emental rate constants, R (secondary amine to primary amine), is obtai ned directly from a simple equation, its value being < 1/2, decreasing with temperature. Our results show that the noncatalytic path is more important than the catalytic one up to 20% of the reaction. Different ial scanning calorimetry (d.s.c.) and gas chromatography-mass spectrom etry (g.c.-m.s.) were used for epoxy and amine quantification respecti vely. G.c-m.s. proved a very powerful technique for quantification of the amine. (C) 1997 Elsevier Science Ltd.