ADDITION OF A REACTIVE DILUENT TO A CATALYZED EPOXY-ANHYDRIDE SYSTEM .2. EFFECT ON ENTHALPY RELAXATION

Enthalpy relaxation in an epoxy resin based on diglycidyl ether of bis phenol A (DGEBA) with a reactive diluent cured with methyl-tetrahydrop hthalic anhydride (MTHPA) with an accelerator was investigated by diff erential scanning calorimetry. The reactive diluent (RD) added was an aliphatic diglycidyl ether which was mixed in a proportion of 50 parts by weight (pbw) per 100 parts of DGEBA, with the stoichiometric quant ity of MTHPA. The key parameters of the enthalpy relaxation investigat ed were the nonlinearity parameter, x, the apparent activation energy, Delta h, and the nonexponentiality parameter, beta. The results were compared with other data obtained previously in similar epoxy-anhydri de systems without an RD but with different degrees of conversion in o rder to analyze the effects of (a) the introduction of aliphatic chain s of the RD in the epoxy structure and (b) a reduction in the crosslin k density of the resin. (C) 1997 John Wiley & Sons, Inc.