Biomimetic PVA hydrogel and MMT reinforced TPU water-lubricated bearing materials for superior frictional properties and wear resistance
Zhiwei Guo, Yu Bi, Zumin Wu, Chengqing Yuan
Abstract
The increasingly stringent emission regulations have greatly encouraged the development of environmentally friendly technologies for ships. Thus the environmentally friendly water-lubricated bearings are progressively replacing the oil-lubricated bearings, which pose oil leakage risks. However, the low viscosity of water results in insufficient thickness and loading capacity of the water film under harsh working conditions including low speed and high load, leading to high friction force, and severe abrasive and adhesive wear of the water-lubricated bearing materials. Inspired by the efficient hydration-based lubrication of human cartilage, the Polyvinyl alcohol (PVA) hydrogel with superior lubrication performance has been introduced into the design of the water-lubricated thermoplastic polyurethane (TPU) composites, while the montmorillonite (MMT) was incorporated to enhance the load-carrying capacity of the composites. The effect of the hydrogel and MMT contents on the frictional properties and wear resistance of the MMT reinforced hydrogel (M-hydrogel)/TPU composites (M-hydrogel/TPU) and hydrogel/MMT reinforced TPU composites (hydrogel/M-TPU) under water-lubricated conditions have been investigated through tribological experiments, wear mass measurement and surface morphologies observation. The results indicate that the M-hydrogel/TPU composites with 1 wt% M-hydrogel exhibited a 71.4 % maximum reduction in friction coefficient and a 79.8 % maximum reduction in wear mass loss compared to the original TPU, and effectively reduced the adhesive wear and abrasive wear of the materials. The lowest friction coefficient and wear mass losses, combined with the smoothest wear surface demonstrate M-hydrogel accounting for 1 wt% can effectively enhance the frictional properties and wear resistance of the M-hydrogel/TPU by forming the hydration layer with superior lubrication performance on the surface of the composites. This research provides a novel approach and experimental foundation for utilizing hydration lubrication, inspired by cartilage, to enhance the frictional properties and wear resistance of water-lubricated bearing materials.