NMR study of phase composition and the process of phase separation in segmented polyurethanes

Pulse NMR methods have been employed to investigate the phase state and the process of phase separation in segmented PUs based on 1,4-butanediol and 4,4′-diphenylmethane diisocyanate with crystallizable (polybutylene glycol adipate) and non-crystallizable as part of PU (polybutylene ethylene glycol adipate) polyesters. For both samples the same Tg of flexible blocks (-20°C) and temperature of the disappearance of the microphase of the rigid blocks (110°C) are observed. The segregation process was found to have two stages with acceleration as the temperature rises in a certain interval. The crystallization processes of the flexible blocks were found to influence the rate of segregation of the rigid blocks. © 1990