Effect of thermal degradation on the mechanical properties of a diglycidyl ether of bisphenol A 1,3-bisaminomethylcyclohexane (DGEBA/1,3-BAC) epoxy resin system

The effect of thermal degradation on the mechanical properties of a diglycidyl ether of bisphenol A (DGEBA)/1,3-bisaminomethylcyclohexane (1,3-BAC) epoxy system, cured with two different curing cycles-a short cycle and a long cycle-were studied using tensile and Izod impact experiments and scanning electronic microscopy, SEM, observations. From these experiments it can be noted a loss of mechanical properties of the material cured with both cycles with aging time, although the material cured with the long cycle presents better properties at any aging time. This better behavior can be explained from the time temperature transformation, TTT, diagram of this system. A good correlation was observed between the decrease in the intensity of the peak of beta transition in tan delta curve obtained by dynamic mechanical analysis, DMA, and the decrease of the Izod impact strength when thermal aging is increasing. Also, a good correlation can be found between the increase in the fragility of the material with aging time and the morphology of fractured surfaces observed by SEM. (C) 1997 John Wiley & Sons, Inc.