Chemorheology of cyanate ester—organically layered silicate nanocomposites

The effect of nanoparticle addition on the flow and curing behavior of a phenolic triazine cyanate ester resin system has been studied using chemorheological, thermal and spectroscopic techniques. While the neat system exhibited Newtonian flow, the nanodispersed prepolymer exhibited pseudoplastic flow behavior, typical of polymeric fluids such as gels and pastes. Evolution of the morphology during curing has been found to be dependent on the rate of intergallery diffusion of the prepolymer and subsequent gelation and vitrification, as well as the intra and extragallery cure kinetics. Curing reactions of the cyanate ester nanocomposite system consisting of a di-functional phenol, a halogen cyanate and organically layered silicates were studied. Gel times were measured as a function of temperature by time sweeps on a controlled stress rheometer. Gelation and vitrification times and activation energies for the nanocomposite systems were lower than that of the neat resins, indicating a catalytic effect of the clays on the curing reaction. Curing kinetics experiments performed on DSC and FTIR confirmed this phenomenon. Based on above experiments, time–temperature-transformation diagrams for the different systems were constructed.