In Situ Analysis of Melt-Drawing Behavior of Melt-Spun Ultrahigh-Molecular-Weight Polyethylene Fibers

In this study, the melt-drawing behavior of melt-spun ultrahigh-molecular-weight polyethylene (UHMW-PE) fibers with different oriented crystalline states was investigated by in situ wide-angle X-ray diffraction (WAXD) measurements. Melt-spun UHMW-PE fibers with different oriented crystalline states were prepared at different take-up speeds. The obtained melt-spun fibers were melt-drawn at 140 °C, and the oriented crystallization behavior during melt-drawing was evaluated by in situ WAXD measurements. Drawing started from a state where molten amorphous and oriented crystals coexisted. As drawing proceeded, the oriented crystallization occurred during melt-drawing. Rapid oriented crystallization occurred for the melt-spun fiber prepared at a high take-up speed with many remaining oriented crystals, indicating the effective transmission of the applied stress through the remaining oriented crystals. On the other hand, gentle oriented crystallization with chain slippage occurred during the melt-drawing of the melt-spun fiber prepared at a low take-up speed with few remaining oriented crystals. The oriented crystallization with chain slippage improved the melt drawability and simultaneously yielded a high crystalline orientation, resulting in melt-drawn fibers with both high tensile strength and small diameter. The findings obtained are important for simultaneously achieving high strength and small diameter of UHMW-PE fibers prepared by melt-processing.