2 TYPES OF PHYSICAL NETWORKS IN CROSS-LINKED SEGMENTED POLYURETHANES

Segmented polyurethanes prepared with a bicomponent curing, agent containing a polyol were shown to be characterized by a network of interchain physical bonds existing outside hard-segment domains. Network parameters of cross-linked polyurethanes prepared with a bicomponent curing agent were estimated, and their variations with temperature and tensile drawing was examined. The effect of each type of network on temperature dependences of the strength and critical ultimate tensile strain of segmented elastomers was studied. A marked decrease in the critical strain of segmented polyurethanes with increasing test temperature was shown to be related not only to the disruption of interchain physical bonds in elastomer but also to the presence of chemical cross-links.