Study of the Effect of Soft-Segment Length and Concentration on Properties of Polyetherurethanes. I. The Effect on Physical and Morphological Properties

Abstract

Abstract 1. Densities of elastomers with crystallizing soft segments were higher than that of the noncrystallizing ones. However, the effect of the soft segment length is not regular and may reflect some specific interactions between two phases as well as instantaneous morphology. 2. Phase inversion as judged by drop of hardness takes place at about ssc=60° or more; a shift to higher ssc gives a greater segment length. 3. Tg of the soft segment in samples with well separated phases is independent of ssc, e.g., the presence of hard phase does not change mobility of the soft phase in samples with ssc=50° or more, in all series. However, Tg is strongly dependent on the soft-segment length. Tg for the soft segment of Mn=650 was −43°C, for Mn=1000 was −62°C, and for Mn=2000, Tg was −75°C. The effect of the presence of the hard phase on mobility of the soft phase seems to vanish for M>2500. 4. Tg of the hard segment at 77°C was clearly observed only in quenched samples with a high hard-segment concentration (80%) and at 93°C in a pure hard segment. 5. Melting of both phases were observed in polymers with long soft segments (Mn=2000). Soft segments of Mn=650 and 1000 do not crystallize. The hard phase crystallizes if its Mn is about 1000 or more or if the degree of polymerization of the hard segment is 3 or above, although exceptions were found in the A series. 6. Spherulitic structures were observed in polymers with low ssc (20% and 40%) polymers and in one with ssc=80°. Thus, both hard and soft phases can form spherulitic structures.