Kinetics of polyurethane formation between glycidyl azide polymer and a triisocyanate

Kinetics of the polyurethane formation between glycidyl azide polymer (GAP) and a polyisocyanate, Desmodur N-100, were studied in the bulk state by using quantitative FTIR spectroscopy. The reaction was followed by monitoring the change in intensity of the absorption band at 2270 cm-l for NCO stretching in the IR spectrum, and was shown to obey second-order kinetics up to 50% conversion. The activation parameters were obtained from the evaluation of kinetic data at different temperatures in the range of 50-80 degreesC. The enthalpy and entropy of activation were found to be DeltaH(double dagger) = 44.1 +/- 0.5 kJ . mol(-1) and DeltaS(double dagger) = -196 +/- 2 J . mol(-1)l . K-1, respectively. Dibutyltin dilaurate (DBTDL) was used as the curing catalyst. The kinetic study of the polyurethane formation between GAP and Desmodur N-100 showed that the reaction is enormously speeded up in the presence of the catalyst, and the reaction obeys second-order kinetics, provided that the catalyst concentration is kept constant. An investigation on the rate of the catalysed reaction depending on the catalyst concentration provided the order of the reaction, with respect to the DBTDL catalyst concentration, and the rate constant for the catalytic pathway of the reaction. The rate constant for the catalytic pathway was established to be 4.37 at 60 degreesC, while the uncatalyzed reaction has a rate constant of 3.88 x 10(-6) L mol-L s(-1) at the same temperature. A rate enhancement factor of 23 was achieved by using 50 ppm catalyst. (C) 2001 John Wiley & Sons, Inc.