Melt processing and structural manipulation of highly linear disentangled ultrahigh molecular weight polyethylene

Abstract

Melt processing of commercial ultrahigh molecular weight polyethylene (UHMWPE, Mη>106g/mol) is an insurmountable bottleneck due to the extremely high melt viscosity arising from its numerous chain entanglements. In the current work, we demonstrated that a UHMWPE (Mη=∼3.4×106g/mol) with a highly linear structure and low entanglements synthesized by a single–active–site Ziegler–Natta catalyst can be melt injection molded without the aid of any additives and, more strikingly, structurally manipulated by means of an intensive shear flow during the packing stage of injection molding. Therewith, large amounts of self-reinforced superstructures, i.e. shish-kebabs and oriented lamellae, were generated in bulk UHMWPE. Appealing interlocked shish-kebabs appeared due to the overstocked shishes that made the epitaxial kebabs penetrate into each other. The self-reinforced superstructures, together with the eliminated structural defects and the increased crystallinity, brought about considerable mechanical enhancement. In particular, the yield strength and ultimate tensile strength of structured linear disentangled UHMWPE were increased by 75% and 71%, from 23.3±0.2 and 40.4±0.6MPa for compression-molded counterpart to 40.8±1.3 and 69.0±0.8MPa, respectively. Our current effort makes a pivotal breakthrough in efficient fabrication of high-performance UHMWPE parts, holding a great prospect towards the application in severe conditions and the instructive effects on synthesis in return.