DYNAMIC MECHANICAL RESPONSE OF MODEL EPOXY NETWORKS IN THE GLASSY STATE

The dynamic mechanical properties of model epoxy-amine networks are investigated in the glassy state over a wide range of frequencies, at temperatures between 123 K and 350 K. The effects of crosslink density and network chain flexibility on the beta-relaxation are examined. Motions responsible for the beta-process begin to develop at the same temperature, whatever the crosslink density. However, an increase in crosslink density is accompanied by an increase in amplitude and a broadening towards high temperatures of both damping tan-delta and loss modulus E". This effect is responsible for the decrease of elastic modulus E' at room temperature with increasing crosslink density.