Kinetic and viscosity relations for thermosetting polyurethanes

Abstract

Kinetic and viscosity relations for polyurethane network polymerization were analyzed. A rigid foam formulation consisting of a polymeric isocyanate (functionality ca. 2.7) and a polyether polyol (functionality ca. 4.5), was selected. The kinetics were studied with adiabatic temperature rise and chemical techniques. An overall second-order reaction and an activation energy, E=51.2 kJ mol−1, were obtained. The viscosity rise was correlated with the reaction extent and the weight average molecular weight. The dependence of viscosity on the latter was of mth order, with m greater than 3.4. This high parametric sensitivity is associated with the formation of branched structures from the beginning of the reaction. © 1983 The Society of Polymer Science, Japan.