The cure of rigid polyurethane encapsulating foam

The disappearance of isocyanate groups in 20 lb/ft{sup 3} rigid polyurethane encapsulating foam (44402-20) was monitored by FTIR spectroscopy leading to an activation energy of 4 kcal/mole. The disappearance of isocyanates can be due to either crosslinking reactions or gas production. Attempting to separate these two reaction paths, we measured the gel time and volume change during cure leading to activation energies of 5 and 6 kcal/mole for the crosslinking and foaming mechanisms respectively. 3 refs., 16 figs.