Bulk polymerization of hydroxyl terminated polybutadiene (HTPB) with tolylene diisocyanate (TDI): A kinetics study using 13 C‐NMR spectroscopy

The bulk polymerization of hydroxyl‐terminated polybutadene with tolylene diisocyanate has been studied in uncatalyzed isothermal reactions. The conversion in urethane was monitored by 13 C‐NMR spectroscopy of the CO function at level up to 70%. Effects of reagents ratio and temperature were investigated. The experimental data were modeled by a set of two competitive second‐order reactions to account for the difference in reactivity of o ‐NCO and p ‐NCO groups of tolylene 2,4 diisocyanate. The apparent kinetic constants calculated appeared to be statistically higher than previous results found in literature from work in aromatic solvents. Deviations from second‐order law were observed during the last stage of polymerization. Activation energies were estimated at 12.3 kJ. mol −1 and 42.8 kJ. mol −1 for the p ‐NCO and o ‐NCO groups, respectively. The difference in their reactivity tended to decrease as temperature of reaction was increased.