HIGH-TEMPERATURE RETARDATION MODE IN EPOXY-AROMATIC AMINE NETWORKS

Due to the specific nature of thermally stimulated creep (TSCr) experiments, complementary data on the high temperature retardation mode in epoxy-aromatic amine networks as observed in dynamic mechanical thermal analysis have been obtained. Two series of amine-cured diglycidyl ether of bisphenol A (DGEBA) networks were investigated by TSCr to characterize their anelastic properties. By systematically varying the amount of methylene dianiline (MDA) used as crosslinking agent, the effect of an excess of epoxy on the network structure was followed. The high temperature retardation mode associated with the glass transition was found to be shifted to higher temperatures with increasing hardener content. This reveals an important restriction of molecular mobility as the resin tends to full crosslinking. It is also important to note that the peak temperature of DGEBA-MDA depends on the crosslink density for aminohydrogen to epoxy ratio r > 0.6 and on number average molecular weight for r < 0.6.