An investigation of the effect of sample preparation on the thermal behavior and the small‐angle x‐ray scattering of a polyurethane block copolymer

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Abstract
The effect of varying sample preparation parameters on the thermal behavior and on the small‐angle x‐ray scattering (SAXS) properties of a polyether polyurethane were investigated. The polyurethane studied was a methylene bis(p‐phenyl isocyanate) (MDI)/butanediol/poly(tetramethylene oxide) (PTMO) system synthesized in a 6/5/1 mole ratio by a two‐step solution polymerization. The PTMO had a nominal molecular weight of 2000. The samples were compression molded under different conditions for the SAXS experiments. The preparation parameters studied included molding time and temperature, sample thickness, and quenching rate from the molding temperature. The molding temperature has the greatest effect on the SAXS data. In this case the domain size was observed to increase as the molding temperature increased from 130 to 200°C. The thermal properties were also found to be strongly dependent on the molding temperature, as measured by differential scanning calorimetry (DSC). An endotherm related to the annealing that occurs during the molding process appears in each sample near the molding temperature. The other preparation parameters have little or no effect on the SAXS and thermal properties of this sample.