Abstract
The kinetics of the cure reaction for a system of bisphenol-S epoxy resin (BPSER), with 4,4′-diaminodiphenyl sulfone (DDS) as a curing agent was investigated with a differential scanning calorimeter (DSC). Autocatalytic behaviour was observed in the first stages of the cure which can well be described by the model proposed by Kamal, using two rate constants, k1 and k2, and two reaction orders, m and n. The overall reaction order, m + n, is in the range 2∼2.5, and the activation energy for k1 and k2 was 86.26 and 65.13 kJ mol−1, respectively. In the later stages, a crosslinked network was formed and diffusion control was incorporated to describe the cure. The glass transition temperature (Tg) of the BPSER/DDS samples partially cured isothermally was determined by means of torsional braid analysis (TBA) and the results showed that the reaction rate increased with increasing Tg, in terms of rate constant, but decreased with increasing conversion. It was also found that the SO2 group both in the epoxy resin and in the hardener increases the Tg values of the cured materials compared with that of BPAER. The thermal degradation kinetics of this system was investigated by thermogravimetric analysis (TGA). It illustrated that the thermal degradation of BPSER/DDS has nth order reaction kinetics. © 2000 Society of Chemical Industry
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