Studies on melt memory effect at extrusion and drawing processes for thermoplastic polyester elastomer.

The melt memory effect of a commercially available thermoplastic polyester elastomer (TPEE) was investigated. Although a main melting peak of TPEE used in this study was located at 208 °C in the differential scanning calorimetry (DSC) heating curve, some crystals still existed even at 220 °C. This was detected as a tail of the DSC endothermic peak. However, these crystals did not affect the extrusion processability; i.e., good extrusion processability was detected at 220 °C without any flow instability, which was evaluated using a capillary rheometer. Polarized optical microscopy (POM) images and two-dimensional wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) patterns showed that the strand extruded at 220 °C exhibited a highly oriented structure, whereas the strands obtained at 230-240 °C showed spherulite texture without any deformation. Moreover, polymer chains in the strand extruded at 220 °C oriented perpendicular to the flow/stretching direction. This anomalous orientation was attributed to the parallel orientation of lamellae, which affected the mechanical properties in the solid state. [ABSTRACT FROM AUTHOR]