Wear Evaluation of Poly(vinyl alcohol) Hydrogel by UV Spectrometry and TOC Measurement of Lubricant

Abstract We report the wear evaluation of poly(vinyl alcohol) (PVA) hydrogel by measuring the polymer concentration in the lubricant after the sliding test. Hydrogels are expected as biomaterials, and wear evaluation is required for their application. However, the swelling and drying behavior of hydrogels makes accurate wear evaluation difficult by applying the same method for solid materials. In this work, sliding tests were conducted, then the microscopic observation of the worn gel sample and the quantitative wear evaluation using the lubricant were performed. To understand the relationship between wear and surface geometry, glass substrates with various surface roughness and hydrogels with different surface geometries were used. UV spectrometry and total organic carbon measurements of the lubricant revealed that the wear amount increases with sliding time or surface roughness of the substrate, and it is possible to quantitatively evaluate the wear of the PVA gel. The effect of surface dimples on the hydrogel was different depending on the counter substance; friction and wear decreased against the glass, but low friction and high wear appeared against the gel. Because there were a few wear scars on the gel with dimples, it was suggested that dimples scrape and trap the generated wear particles, reducing the transfer of wear particles and surface damage. Measuring the concentration of PVA polymers in the lubricant made it possible to separately and quantitatively evaluate whether the wear of the gel was due to surface deformation and transfer, or loss due to surface damage.