Ultimate Tensile Properties of Segmented Polyurethane Elastomers. Factors Leading to Reduced Properties for Polyurethanes Based on Non-Polar Soft Segments. Revision

摘要

Polyurethane block copolymers based on non-polar soft segments such as polyisobutylene, polybutadience, and polydimethylsilozane possess some desireable chemical and transport properties compared with conventional polyether or polyester polyurethanes. Unfortunately, the reported tensile properties on non-polar soft segment based polyurethanes are poor relative to those of conventional polyurethanes. Several explanations for this behavior have been suggested based on differences in soft segment functionality, molecular weight, glass transition temperature, crystallizability, and compatibility with the hard segments. These explanations are examined in light of the literature and some new experimental results. All of the above factors can lead to poor tensile properties; however, the only inherently limiting factors on the tensile properties of polyurethanes based on non-polar soft segments appear to be a lack of soft segment crystallizability under strain and possible an excessively high degree of phase separation. Additional work is needed to more fully understand the effects of the variables listed above.