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

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.