Balancing Processability and Tribological Performance of UHMWPE/HDPE Composites via KH570-Functionalized Nano-SiO2 Reinforcement

Abstract Water-lubricated bearings require polymer composites with low friction, high wear resistance, and favorable processability under boundary and mixed lubrication, however, simultaneously achieving these characteristics is still challenging. Ultra-high molecular weight polyethylene (UHMWPE) shows excellent tribological performance, whereas its exceedingly poor melt processability limits practical fabrication. Blending UHMWPE with HDPE can enhance processability, but it often comes at the expense of wear resistance. To overcome this trade-off, KH570-modified nano-SiO2 was mixed with UHMWPE/HDPE (20/80) composites through melt blending followed by hot pressing. The impact of SiO2 content on crystallization performance, mechanical characteristics, rheological response, melt flow rate, and tribological performance was systematically investigated. The composite containing 0.4 wt % SiO2 exhibited the best overall performance. Under dry sliding conditions, it achieved a minimum coefficient of friction (COF) of 0.05 and a wear rate of 0.82 × 10−5 mm3/(N·m). Under seawater lubrication, the minimum COF was 0.07, with a wear rate of 1.03 × 10−5 mm3/(N·m). Compared with pure UHMWPE, the composite showed a 16% reduction in wear rate under dry sliding, although its wear rate increased slightly under seawater lubrication. The composite containing 0.4 wt % SiO2 achieved the optimally overall performance, with a minimum friction coefficient of 0.05 and a wear rate of 0.82 × 10−5 mm3/(N·m), representing a 16% reduction in wear rate relative to neat UHMWPE, while also boosting processability. These improvements are ascribed to the even dispersion of nanoparticles, enhanced interfacial adhesion, and the creation of a more robust transfer film. Overall, this study offers a practical strategy for balancing processability and tribological performance in polyethylene-based composites and provides useful guidance for developing wear-resistant materials for water-lubricated bearing applications.