Polybutadiène hydroxytéléchélique, 7. Cinétique de polycondensation en solution et en masse du polybutadiène hydroxytéléchélique avec le méthylène‐4,4′ di(isocyanate de phényle) en l'absence de catalyseur. Etude par ¹H NMR et ¹³C NMR

Abstract

Abstract Quantitative determinations by 13 C NMR performed with insoluble polyurethanes allow to study the kinetics of the polymerization in bulk between hydroxytelechelic polybutadiene G 1000 and 4,4′‐methylene diphenylisocyanate (MDI). Comparisons have been made with (G 1000 + MDI) polymerization and (monoalcohol or G 1000 + phenyl isocyanate) model reactions in toluene. With [NCO]/[OH] = 1 and T ⩽ 60°C, in solution as well as in bulk, conversions are not complete. Because of the presence of gels, part of the reactive functions have been found to be trapped. For kinetic tests, only the first stage of the polymerization (conversion < 70%) may be taken into account. In bulk, the two alcohol functions are equally reactive, whereas in toluene, the hydroxylated 1,4 ends of the polybutadiene chains are more reactive. As evidenced for model reactions in the foregoing paper of this series, the kinetics fit better with the 3rd order than with the 2nd order equation. Nevertheless, at higher temperatures, the 2nd order may be used. The autocatalysis phenomenon found effective for model reactions is negligible in polymerization. All kinetic constants and activation parameters calculated must be considered to be apparent ones only.