In situ study on the tensile deformation in high-density polyethylene/hexagonal boron nitride composite

Tensile deformation in the post processing of polymer plays a critical role in determining its mechanical properties. In this work, we investigated the structure evolution of high-density polyethylene/hexagonal boron nitride (HDPE/h-BN) composite during stretching in a wide temperature range from 25 °C to 100 °C in order to reveal the suitable post processing temperature of HDPE/h-BN composites fiber. The structure transition of HDPE crystal and the distribution of h-BN were investigated by in-situ small-angle X-ray scattering (SASX), in-situ wide-angle X-ray diffraction (WAXD) measurements, and scanning electron microscopy (SEM). The result shows that the parent HDPE crystal would be broken and recrystallize into highly oriented daughter crystal along the tensile direction when the tensile temperature (Tten) is in the range from 70 °C to 100 °C, though the recrystallization rate is low at high Tten. When Tten is low (25 °C), the crystallinity decreases continuously as no recrystallization takes place. In addition, the h-BN migrates accompany with the HDPE matrix and becomes oriented during the tensile direction. Combining the result of WAXD, SAXS, and the SEM measurement, it is concluded that the temperature of 70 °C is suitable for post processing of the HDPE/h-BN composite fiber.