Relationship between phase structure and mechanical properties of polyurethane prepared from copoly(PPO-THF) diols

The phase structure of polyurethanes prepared from copoly(PPO-THF) diol with two different process histories, as-molded and solution-cast, was investigated by FTIR and DSC. The mechanical properties of the polyurethane samples were measured. As compared with as-molded samples, IR studies showed that solution-cast samples had a higher fraction of hydrogen-bonded carbonyl groups and a soft domain with less dissolved hard segment, and D SC studies demonstrated that they had a higher degree of phase separation and a hard domain with a higher proportion of ordered region and degree of order. Mechanical measurements showed that solution-cast samples had a higher Young's modulus, elongation to breaking point and stress at breaking point; in particular, when the hard segment content was 50 wt%, doubled values of these properties were obtained. The reason for the improved mechanical properties is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.