RHEOKINETICS OF CURE OF EPOXY-AMINE SYSTEM NEAR THE GLASS-TRANSITION

The methods of viscometry, dynamo-mechanical spectroscopy, differential scanning calorimetry, and IR spectroscopy were used to investigate the process of cure of composite on the basis of DGEBA epoxy resin (Russian trade mark ED-20) and amine curing agent. The temperature intervals both above and below the glass transition temperature of the fully cured composite were studied. It was found that time dependence of chemical conversion, as measured by DSC and dynamo-mechanical spectroscopy, can be described in terms of an equation accounting for the effect of autoacceleration. The parameters appearing in this equation can be determined independently from calorimetric and theological measurements. It is shown that both methods give essentially the same values of these parameters. At low temperatures, the curing reaction proceeds until complete vitrification of the system. After vitrification, the rate of the reaction appreciably diminishes, and further changes in the elastic modulus are mainly governed by relaxation processes.