Hard‐segment domain sizes in MDI/diol polyurethane elastomers

Abstract

Abstract Wide‐angle x‐ray line broadening methods have been used to determine the crystallite size and degree of distortion for the crystalline hard domains in MDI/diol polyurethane elastomers. Crystallite widths have been determined from the integral breadths of the 00 l reflections following correction for distortions of the second kind according to the method Hosemann for polymers prepared using ethylene glycol, propandiol, butandiol, and hexandiol as the chain extender. These data relate to the width of the crystallites along the chain axis and thus can be interpreted in terms of the morphology of the hard domains. The crystallite sizes increase and the distortions decrease with increasing elongation and annealing time, and the sizes tend toward asymptotic values which correspond approximately to the average lengths of the hard‐segment chains. These results rule out any appreciable folding of the hard‐segment chains and point to a model for the hard domains formed by lateral aggregation of extended hard segments.