Cure monitoring of catalysed cyanate ester resins

The cure behaviour of two bisphenol A-based cyanate ester resins, AroCy B10 and B30, catalysed by copper acetylacetonate and nonylphenol was studied. For this purpose, differential scanning calorimetric (DSC) and rheological measurements were carried out at temperatures between 130 and 170°C. The cyanate conversion profiles are fitted with a second-order rate law in the kinetically controlled regime where a good time-temperature superposition is attained. However, it is necessary to add an empirical kinetic term to give a good description of the entire range of curing. Simultaneously, times to gelation and vitrification have been determined by dynamic rheological measurements over the same temperature range. The corresponding conversions have been calculated by correlation of rheological and DSC data, the vitrification conversion being slightly higher for the prepolymer. Independent of the cure temperature, a good correlation between cyanate conversion and glass transition temperature was obtained. The isothermal time-temperature-transformation diagrams for these systems are constructed from the kinetic model and the DiBenedetto equation, and show good agreement with the experimental data.