Effect of Stirring Speeds on Microstructure Formation During Thermoplastic Polyurethanes Synthesis

Abstract

ABSTRACTTwo types of thermoplastic polyurethanes (TPUs) with the same chemical compositions, but with different stirring speeds during the synthesis process, were prepared by a one-step bulk polymerization process. The distinct microstructures of these two samples were characterized in a comprehensive way from primary to tertiary structure. 13C NMR spectra revealed distinctly different characteristics of hard and soft segments' distribution between these two samples. Static light scattering showed the differing mean square radii of gyration and the corresponding secondary structure features. The crystallite features, interface thicknesses, and morphology characteristics of these two samples were studied by differential scanning calorimetry, wide-angle X-ray diffraction, small angle X-ray scattering, and atomic force microscopy. Finally, the mechanism of synthesis was investigated, and a schematic diagram was presented to illustrate the effect of diffusion-controlled phenomena on the propagation of TPUs. Based on the schematic diagram, the formation of distinctly different microstructures due to different stirring speeds could be explained effectively.