Kinetics of Formation of Heterocyclic Polymer Networks. 4. Storage Time Effect

Abstract

The effect of the time of preliminary storage at room temperature on the kinetics of HMDI trimerization at the fixed HMDI/ER ratio (85/25), and different concentrations of the catalyst, TEA, and the evolution of glass transition parameters of the end products in function of the curing reaction regime, were studied by calorimetry. It was established that both the activation energy Eα and the pre-exponential factor ln A increased, the longer the storage time, and both tended to decrease with the conversion α1 The time for the onset of gelation tgel decreased, the higher the catalyst concentration and/or the longer the preliminary storage time the former proved to be a major factor controlling tgel|. The glass transition temperatures Tg for post-cured samples of series HT “internally diluted” with stiff oxazolidone heterocycles were systematically higher than those for samples of series LT cured at 393 K whatever the catalyst concentration and/or the storage time.