Chemorheological study of phosphorylated flame retardant epoxies

Abstract

The aim of this work is to study the chemorheology of the phosphorylated novolac epoxy used in flame retardants. The rheological properties are measured by a parallel plate viscometer and are combined with the kinetics of the curing reaction to explore the conversion dependent character of the viscosity. It was found that dynamic viscosity is a unique function of the effective shear rate over a wide range of frequencies and strains after being corrected for temperature. The effective shear rate dependence of the viscosity is described with a power law with an exponent that depends on the conversion. The effect of temperature is described with an Arrhenius type equation with conversion dependent parameters. Differential scanning calorimetry was applied to determine the kinetic equation that is used, in combination with the thermal history, to obtain the conversion during the rheological measurements. Time–cure–temperature modelling was applied to study a variety of factors that had an influence on the chemorheology. It was also found that the Cox–Merz relation can be utilised to correlate the dynamic viscosity data to the shear viscosity data. The Castro–Macosko model is proposed when considering the combination effects of shear thinning viscosity and reaction kinetics.