Friction characteristics of a potential articular cartilage biomaterial

Many biomaterials are being developed to repair or replace articular cartilage. One of these materials, a poly(vinyl-alcohol) cryogel (PVA-c) may exhibit the mechanical properties required to withstand the harsh environment of diarthrodial joints. To better understand how PVA-c friction is affected by different variables employed in bench top testing to simulate joint conditions, a six-factor, two-level fractional-factorial experiment was developed. Factors included temperature, lubricant, material stiffness, load, sliding speed, and surface roughness. Static and dynamic friction were found to depend significantly on material stiffness and roughness, increasing as material stiffness and roughness increased. Dynamic friction was also inversely proportional to sliding speed. Overall static and dynamic friction for all variables was 0.285±0.091 and 0.143±0.066 (average±S.D.), respectively. Material deformation and other factors may have contributed to the higher than expected friction levels. Frictional behavior of this PVA-c against stainless steel does not follow Amonton's friction law, nor does it follow friction models based on repulsion and adsorption theories.