Rheokinetics of Ring-Opening Metathesis Polymerization of Bio-Based Castor Oil Thermoset

Abstract

Ring-opening metathesis polymerization (ROMP) of norbornenyl-functionalized castor oil has been evaluated using small-amplitude oscillatory shear flow experiments as a function of angular frequency, temperature, and curing time. At the onset temperature of the curing process, an abrupt increase in dynamic shear moduli, G′ and G″, and complex shear viscosity, η*, was observed during the dynamic temperature ramps (2 °C/min heating rate) of the sample over a wide range of angular frequencies. A dramatic increase in zero-shear viscosity, η0, was also observed at the gelation temperature, Tgel. The value of Tgel obtained from the abrupt increase in η0 was found to be in good agreement with the value evaluated from the crossover point of G′ and G″. The real time curing kinetics was investigated under isothermal conditions over a wide range of angular frequencies at different constant curing temperatures (40, 45, 50, and 55 °C). The isothermal gelation kinetics was found to be strongly curing temperature depende...