KINETICS OF POLYCYCLOTRIMERIZATION OF 4,4'-THIODIPHENYLCYANATE

Polycyclotrimerization of 4,4'-thiodiphenylcyanate was studied by mean s of differential scanning calorimetry. Samples of different impurity levels or different catalyst loadings (n-nonylphenol (NP), 1 to 10 phr ) were studied. In the absence of added catalyst, the sample with high er impurity level (most likely residual water) underwent polycyclotrim erization at a lower temperature range than the sample of comparativel y higher purity, although both samples shared the same apparent activa tion energy (E(a) = 93 kJ mol(-1)) and exhibited similar autocatalysed first-order characteristics. The lowering of the reaction temperature range was more significant in the presence of NP. Interestingly, kine tic features in this case were quite different from the uncatalysed co unterpart: in addition to the expected decrease in the apparent activa tion energy (E(a) = 75 kJ mol(-1), independent of the catalyst concent ration), the cure reaction followed an autocatalysed second-order kine tics. These observations are explained in terms of a mechanistic schem e in which the competition between hydroxyl-catalysed and autocatalyti c paths is considered. In particular, formation of NP aggregates ((NP) (m), where m approximate to 7) is proposed to account for the less-tha n-additive catalytic capacity with increasing NP level.