Curing of diepoxides with tertiary amines: Influence of temperature and initiator concentration on polymerization rate and glass transition temperature

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Abstract
The cure of an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA), with benzyldimethylamine (BDMA), was investigated using differential scanning calorimetry. The kinetics showed a first‐order behavior with respect to both epoxy and tertiary amine concentrations and a non‐Arrhenius dependence on temperature. An activation energy could be defined only in the low‐temperature range, i.e., from 80 to 120°C. Its value (E = 24.2 kJ/mol = 5.8 kcal/mol) indicates a very slight dependence on temperature. The glass transition temperature of epoxy networks decreased with an increase in both the tertiary amine concentration and the cure temperature. These effects are attributed to plastification by the free amine and to the decrease in the average length of polyether chains, which, in turn, increases the number of network defects.