EFFECT OF A CURING ACCELERATOR ON THE GLASS-TRANSITION TEMPERATURE OFNONSTOICHIOMETRIC EPOXY-AMINE NETWORKS

Networks were prepared from Bisphenol A diglycidylether and 4,4'-diami nodiphenylmethane both in the presence of different amounts of imidazo le and in the absence of any accelerator. The ratio of epoxy groups to amino hydrogen was varied: the networks were made with amino hydrogen excess, a stoichiometric ratio of epoxy groups to amino hydrogen, and an epoxy excess. The resulting networks were investigated by thermome chanical analysis, by torsion pendulum analysis and by uniaxial compre ssion modulus measurements in the rubbery-plateau zone. Further charac terization was done by sol gel analysis of the cured samples. It was s hown that imidazole does not significantly influence the glass transit ion temperature and the soluble content of the samples if an excess of amino hydrogen was used. In the case of a stoichiometric ratio of epo xy groups to amino hydrogen and in the case of an epoxy excess, imidaz ole considerably influences the glass transition temperature of the ne tworks. A dependence of the soluble content of the samples on imidazol e concentration used for network synthesis was found mainly in epoxy e xcess systems.