Rheological study of the isothermal reticulation of an epoxy resin

The complex modulus of shearing G* = G' + jG″ was measured during the isothermal hardening of several epoxy resins. The gelation induces a slowing down of the rate of growth of viscous modulus ν″ = d(log G″)/dt between two zones where this rate is constant. This slowing down of growth rate varies with the temperature and is null for T = TC gel: ν″2 −ν″1 = K(1/TC gel −1/T). We have shown that the two phenomena of gelation and vitrification stay perfectly distinct at all temperatures and in particular at TC gel. So the decrease of the rate ν″ associated with gelation disappears at this temperature without the vitrification being responsible.