Industrial fabrication of high-performance polyethylene fibers via melt-spinning and multistage drawing

During the preparation of melt-spun high molecular weight polyethylene (HMWPE) fibers, the hot-drawing stage largely determines molecular chain orientation, crystalline structure evolution, and the resulting mechanical properties of the fibers. Moreover, a systematic understanding of how multistage drawing parameters and molecular architecture jointly govern drawing behavior and structural evolution remains incomplete. Herein, linear polyethylene feedstocks with wide (WPE), medium (MPE), and narrow (NPE) molecular weight distributions were melt-spun into fibers. By integrating multistage hot-drawing with heat-setting, the effects of stage-wise draw ratio, temperature, and residence time on drawing behavior, microstructural evolution, and mechanical performance were systematically investigated. Compared with three-stage drawing, two-stage drawing was found to be sufficient to effectively activate the chain orientation potential. When the first-stage draw ratio was fixed at 10, the maximum total draw ratios of WPE, MPE, and NPE fibers reached 34.42, 32.13, and 31.94, respectively. At identical total draw ratios, multistage-drawn fibers exhibited higher tensile strength, knot strength retention, and creep resistance than their single-stage-drawn counterparts. Subsequent heat-setting further released residual stresses, resulting in a pronounced reduction in dry-heat shrinkage. Notably, the WPE-M30-135 fiber, prepared by two-stage drawing at a total draw ratio of 30 followed by heat-setting at 135 °C, achieved a tensile strength of 1.96 GPa, a knot strength retention of 84.51%, and a creep rate as low as 0.87% at 25 °C. Structural analyses reveal that long tie molecules spanning 4 or more lamellae facilitate crystal fragmentation and reorganization, resulting in refined crystallite size and enhanced molecular orientation, thereby improving mechanical performance. This work provides systematic theoretical and practical guidance for optimizing multistage hot-drawing in HMWPE melt-spinning and presents a viable pathway toward the green and efficient production of high-performance polyethylene fibers.