Moisture curing kinetics of isocyanate ended urethane quasi-prepolymers monitored by IR Spectroscopy and DSC

The study of the kinetics of the curing of isocyanate quasi-prepolymers with water was performed by infrared spectroscopy and differential scanning calorimetry. The influence of the free isocyanate content, polyol functionality, and of the addition of an amine catalyst (2,2'-dimorpholinediethylether) in the reaction kinetics and morphology of the final poly(urethane urea) was analyzed. A second-order autocatalyzed model was successfully applied to reproduce the curing process under isothermal curing conditions, until gelation occurred. A kinetic model-free approach was used to find the dependence of the effective activation energy (E-a) with the extent of cure, when the reaction was performed under nonisothermal conditions. The dependence of E, with the reaction progress was different depending on the initial composition of the quasi-prepolymer, which reveals the complexity of the curing process. (C) 2007 Wiley Periodicals, Inc.