Nanoscale effects of TiO₂ nanoparticles on the rheological behaviors of ultra-high molecular weight polyethylene (UHMWPE).

Abstract

Considering the molar mass between entanglements to be an intrinsic property of ultra-high molecular weight polyethylene (UHMWPE), the number of entanglements per chain increases with increasing molar mass, correspondingly making the UHMWPE intractable. Herein, we dispersed TiO₂ nanoparticles with different characteristics into UHMWPE solutions to disentangle the molecular chains. Compared with the UHMWPE pure solution, the viscosity of the mixture solution declines by 91.22%, and the critical overlap concentration increases from 1 wt% to 1.4 wt%. A rapid precipitation method was utilized to obtain UHMWPE and UHMWPE/TiO₂ composites from the solutions. The melting index of UHMWPE/TiO₂ is 68.85 mg, which is in sharp contrast to that of UHMWPE which is 0 mg. We characterized the microstructures of UHMWPE/TiO₂ nanocomposites using TEM, SAXS, DMA, and DSC. Accordingly, this significant improvement in processability contributed to the reduction of entanglements and a schematic model was proposed to explain the mechanism by which nanoparticles disentangle molecular chains. Simultaneously, the composite demonstrated better mechanical properties than UHMWPE. In summary, we provide a strategy to promote the processability of UHMWPE without sacrificing its outstanding mechanical properties.