CHEMORHEOLOGY OF POLY(URETHANE ISOCYANURATE) FORMATION/

Poly(urethane/isocyanurate) is a major resin used in the structural re action injection molding (SRIM) process. In this study, the kinetics a nd viscosity changes of a poly(urethane/isocyanurate) resin were inves tigated by the adiabatic temperature/viscosity rise method and differe ntial scanning calorimetry. The effect of the catalyst concentration a nd the volume ratio of isocyanate to polyol was investigated. It is fo und that isocyanate trimerization depends on the diffusion effect resu lted from the urethane formation. A kinetic model including the diffus ion effect is developed, which is able to predict the experimental res ults. The reaction induced viscosity rise depends on the concentration and the molecular weight of the formed polymer. The measured adiabati c viscosity rise correlates well with the calculated molecular weight growth using the recursive method.