Cure kinetics studies of cyanate ester and bisphenol-F epoxy blend

Abstract

Cyanate ester and Bisphenol-F blends with manganese acetylacetonate in nonylphenol as catalyst and cocatalysts respectively is an attractive candidate as the insulation impregnation materials for fusion grade magnets winding packs that is required to be operating in moderate irradiated environments in fusion devices like Tokamaks. The curing kinetics of this blend system as a thermosetting polymer has been investigated in this paper in detail for 60 : 40 (epoxy:ester) composition strongly driven from application interests. The order of reactions in both chemical kinetics controlled region as well as diffusion controlled regimes have been experimentally found out using Differential Scanning Calorimetric (DSC) studies.Corresponding rate constants and associated cure kinetics have been consequently determined. The second order kinetic model, as it is found, does not fit in to the epoxy-cyanate ester reaction mechanism. The results, therefore,have been discussed in the context of widely used autocatalytic models and variable ‘‘n’’ kinetics models appropriate for chemical controlled region. The reaction conversion rate da/dt of the cyanate ester-epoxy blend is more rapid in chemical controlled regime compared to that in the diffusion controlled regime. The order of reaction is not constant throughout the reaction and is higher in chemical controlled regime. The variable ‘‘n’’ kinetic model has been employed to determine the hypothetical temperature(350.81 K) below which no more curing reaction would occur. The activation energy and the pre-exponential factors have been determined in the chemical controlled regime using Arrhenius reaction.