| Popis: |
Transmission electron microscopy and small angle X-ray scattering techniques have been applied to investigate the bulk morphology of compression moulded samples of an amorphous segmented polyurethane system. Samples of different hard segment content, from 13% to 74% by weight, were synthesized by solution polymerization, so that the hard segment sequence length distribution of each sample approximated the most probable distribution. Microscopy results indicate that meandering cylinders of the soft segment phase are present in the 74% sample. An alternating plate-like structure is found in the 52% sample. However, for samples of hard segment content lower than 50%, results from electron microscopy were inconclusive. The Percus-Yevick hard sphere liquid theory taking into account the polydispersity of domain size was applied to calculate the scattering behaviour of these lower hard segment content samples and compared with the experimental data. Modelling results and mechanical behaviour of these samples lead to the conclusion that discrete hard segment domains of anisotropic shape are present in the soft segment matrix. This conclusion is also supported by the results from calculations of specific area of domains. A spectrum of morphologies varying with sample composition is thus obtained for this particular system of polyurethanes. |
