Isothermal Curing of a Dicyanate Ester Monomer Up to the Gel Point as Studied by Size Exclusion Chromatography

The curing of a dicyanate ester of bisphenol A with and without cobalt(II) acetylacetonate/nonylphenol and with copper(II) acetylacetonate/nonylphenol catalysts was analyzed until the gel point using size exclusion chromatography (SEC). This technique can be used to determine the overall dicyanate conversion as a function of time in the pre-gel state at different curing temperatures (between 130°C and 220°C according to the system). The results have been compared with those obtained by curing the same system by differential scanning calorimetry, showing good agreement. The data obtained indicate that the rate of reaction in the pre-gel stage is kinetically controlled and can be fitted with a second-order reaction with respect to the disappearance of cyanate groups. Apparent activation energies in the range 69-72 kJ/mol have been obtained from the rate constants. Experimental data on gelation times give activation energies around 70-77 kJ/mol, in accord with previous values.