Reaction kinetics and chemorheology of a highly reactive PU system

The reaction kinetics and chemorheology of a fast polymerizing thermoset polyurethane (PU) system composed of 4,4-diphenylmethane diisocyanate, poly(propylene oxide) triol, and dibutyltin dilaurate (T₁₂) as a catalyst was investigated. The adiabatic temperature rise measurements were carried out to analyze the reaction kinetics of the PU system since polymerization rate was so fast. A second order Arrhenius type reaction kinetic equation could describe well the reaction kinetics of the PU system. The power with respect to the catalyst concentration was about 0.6. Viscosity change of the PU system with low catalyst concentration during isothermal polymerization was measured using a rheometer. A viscosity function was estimated from the rheometer data and the kinetic data through nonlinear regression. The power law index with respect to the weight average molecular weight was dependent on the isothermal cure temperature.