Curing Kinetics and Thermal Properties Characterization of o-Cresol-formaldehyde Epoxy Resin and MeTHPA System

Abstract

The kinetics of the cure reaction for a system of o-cresol-formaldehyde epoxy resin (o-CFER) with 3-methyl-tetrahydrophthalic anhydride (MeTHPA) as a curing agent and N,N-dimethyl-benzylamine as an accelerator was investigated by means of differential scanning calorimetry (DSC). Analysis of DSC data indicated that an autocatalytic behavior showed in the first stages of the cure for the system, which could be well described by the model proposed by Kamal, which includes two rate constants, k1 and k2, and two reaction orders, m and n. The activation energy E1 and E2 are 195.84 and 116.54 kJmol−1, respectively. In the later stages, the reaction is mainly controlled by diffusion, and a diffusion, factor, f(α), was introduced into Kamal's equation. In this way, the curing kinetics were predicted well over the entire range of conversion. Molecular mechanism for the curing reaction was discussed. The glass transition temperature Tg was determined by means of torsional braid analysis (TBA). The results showed that Tgs increased with curing temperature and conversion up to a constant value about 367.1 K. The thermal degradation kinetics of the system was investigated by thermogravimetric analysis (TGA), which revealed two decomposition steps.