on the elongation vs SSC curves were observed. The slope of the linear part from
0 to about 50% SSC was lower than that of the line in the region above 50%
SSC. The intersection at about 50% SSC was associated with the phase inversion.
Takahara et al. 2°9 investigated structure and properties of MDI/ED/polyol
polyurethane where polyols were based on PEO, PPrO, PTMO and PBD, of
different molecular weights. Since MDI/ED/polyol molar ratio was kept constant
at 2 : 1 : 1, by varying the molecular weight of the polyols from 400 to 4000,
soft segment concentration was varied from about 42% to 88%. Here, hard
segment length was kept constant and both SSC and molecular weight of the
polyols were changed together. Tensile strengths of PEO, PPrO and PTMO
series vs SSC are presented in Fig. 38. Comparisons of tensile strengths at high
soft segment concentrations illustrate the better mechanical strength of PTMO