Preparation of Ultrahigh-Molecular-Weight Polyethylene Tapes by Multiple Melt Processing

Ultrahigh-molecular-weight polyethylene (UHMW-PE) tapes are commercially prepared by skiving a compacted block of UHMW-PE powder. However, the mechanical properties of a skived film are poor, and the production of a thin film is difficult. In this study, we succeeded in preparing UHMW-PE tapes from UHMWPE reactor powder by multiple melt processing, i.e., melt-extrusion, melt-rolling, and melt-drawing. UHMW-PE reactor powder was continuously melt-extruded into a strand without melt fracture. The obtained melt-extruded strand was repeatedly melt-rolled at 155 and 150 ̊C in order and with stepwise reduction of the gap between the rolls to form a tape. The obtained tape (as-rolled tape) was melt-drawn at 155 ̊C to achieve high tensile strength and thin thickness. The maximum draw ratio (DR) was the highest under a strain rate of 5/min. The development of the crystalline structure of the melt-drawn tapes was investigated by wide-angle X -ray diffraction measurements and differential scanning calorimetry measurements. Extended-chain crystals (ECCs) were formed by melt-drawing of the as-rolled tape and developed with increasing DR, resulting in high tensile strength. The melt-drawn tape prepared by melt-drawing with DR of 15 under a strain rate of 5/min exhibited the most enhanced ECC formation and the highest degree of crystalline orientation, resulting in a tensile strength of 0.56 GPa and a thickness of 70 µm. Consequently, a thin UHMW-PE tape with superior tensile strength was prepared from UHMW-PE reactor powder by multiple melt processing.