dc.description.abstract | Cure behavior of cyanate ester and its blends with polyphenylene oxide(PPO)of various compositions were studied using differential scanning calorimetry(DSC)and FTIR. The reaction rates of the cyanate ester blends were found to be higher than that of the neat cyanate ester , and the total heat of reaction decreased with increasing PPO. The effects of PPO content on the cure behavior in the cyanate ester/PPO blends were investigated with FTIR. FTIR analysis reveals that the cyanate functional group reactions are accelerated by adding PPO. This is caused by the reaction of cyanate ester with PPO phenolic end-group and water yielding imidocarbonate and carbamate intermediate which can react with cyanate ester to form cyanurate. The experimental data, showing an autocatalytic behavior, were compared with the model proposed by Kamal, which includes two rate constants, k1 and k2, and two reaction orders, m and n. This model gives a good description of cure kinetics up to the onset of vitrification. With the inclusion of a diffusion factor (f(a)) into this model, it was, however, possible to predict with precision the cure kinetics over the whole range of conversion. During cure , the phase separation induced by the step-growth polymerization of the monomer. The fracture surface of blends was examine using scanning electron microscopy(SEM). At low PPO content(10 and 20phr), the phase separation takes place via nucleation and growth (NG). At high PPO content(30phr and 50phr), the phase separation takes place via spinodal decomposition (SD). The results from TGA weight loss profiles indicate that onset decomposition temperature was decreased by the incorporation of PPO. This is caused by that the presence of PPO lowers crosslink density of cyanate ester blends. High-temperature stability decreased with increasing PPO. | en_US |