EFFECTS OF CHEMICAL-STRUCTURE OF HARDENER ON CURING EVOLUTION AND ON THE DYNAMIC-MECHANICAL BEHAVIOR OF EPOXY-RESINS

A diglycidyl ether of bisphenol-A-type difunctional epoxy resin was cured with different amine-type curing agents at stoichiometric ratios. The crosslink process was followed by viscosimetry and differential scanning calorimetry. The gelation time and the apparent activation energy were found to be strongly dependent on the structure of the hardener. The heat of reaction did not vary significantly when the hardener was changed. An interpretation based on structural aspects such as amine reactivity, steric hindrance, and chain rigidity is proposed for the variations corresponding to the curing process. Master viscosity curves have been built up for all mixtures. The effect of the hardener on the glass transition temperatures of the different mixtures has been analyzed taking into account the crosslink density, measured by the rubber modulus obtained by dynamic mechanical studies, and the chemical structure of the hardener chains. (C) 1995 John Wiley and Sons, Inc.