Effect of Nano-Silica on Enhancing Slip Resistance of UHMWPE in Slippery Environment

The Ultra High Molecular Weight Polyethylene (UHMWPE) is gradually adopted to manufacture the surface material of ship’s deck due to its satisfactory wear-resistance, corrosion resistance and light weight. The slippery, wave impact and turbulent environment of ship deck seriously affect the balance of equipment and personnel on deck, and then challenge the reliability and threaten personal safety of crew. The nano-silica (SiO₂) with high hardness and excellent friction-increasing performance was used as modifying filler to enhance the slip-resistance of UHMWPE in water environment in this study. The effects of different volume fractions of nano-SiO₂ on the frictional behaviors of modified UHMWPE in the frictional processes were investigated by setting the gradient increasing nano-SiO₂ addition volume fraction. The results showed that the addition of nano-SiO₂ changed the tribological behaviors of UHMWPE composite, which was mainly manifested in the increase of friction coefficient and surface roughness of wear surfaces, and then improved its slip-resistance performance of UHMWPE composite. On the one hand, nano-SiO₂ weakened the water-wettability and water-absorbability of modified UHMWPE composites, and made the contact angle of UHMWPE composite increased from 75.6° of pure UHMWPE to 94.5° of modified composite with 4.0% volume fraction of nano-SiO₂. Thus, the hydrophilic of modified UHMWPE gradually changed into hydrophobic, which resulted in improving the slip-resistance performance in wet or slippery environment. On the other hand, the hard nano-SiO₂ particles were not easy to deform comparing to the soft UHMWPE, and gradually exposed themselves to the wear surfaces of the modified UHMWPE during the frictional process, and formed the micro-convex body on the wear surface of modified UHMWPE composite. Then, they contacted with the silicon nitride ceramic ball directly, which resulted in the meshing phenomenon with the ceramic ball under the action of external load. Therefore, the friction force mainly came from the meshing actions among of the contact points on the surfaces of modified UHMWPE and ceramic ball during the frictional process. Moreover, the nano-SiO₂ reduced the bending strength, tensile properties and tear strength of the material, which made the modified UHMWPE composite deform easily, and increased the roughness of the wear surface. The surface roughness of UHMWPE composite increased from 3.670 μm for pure UHMWPE to 5.604 μm for modified composite UHMWPE with 4.0% volume fraction of nano-SiO₂. With the gradually increasing of the volume fraction of nano-SiO₂, the deformation behavior of the wear surface of modified UHMWPE composite became more and more serious, and increased the surface roughness. The meshing wear between the modified composite UHMWPE and the silicon nitride ceramic ball was reinforced, which resulted in increasing the frictional force and the coefficient of friction, and eventually the friction coefficient of modified composite UHMWPE reached 0.124, and was very closed to dry friction. This study provided experimental support and theoretical basis for the design and manufacture of a kind of polymer composite material which can improve the slip resistance of ship deck in slippery environment.