Wear and friction behavior of polyacetal surfaces with micro-structure controlled surface pressure

Macro-scale surface patterns are often used with tool and working surfaces to improve gripping, sliding or other working abilities. Polyacetal (POM) samples possessing micron-scale surface structures were examined to determine effects of micro-scale patterning on the sliding friction and wear rate of POM surfaces. The micro-patterned samples were manufactured via injection molding and their friction/wear behaviors were compared to those of identically micro-patterned polypropylene (PP) surfaces. Polymer surfaces were slid against polished steel using a reciprocating pin-on-disk type measuring system. The wear and friction properties of the patterned polymers were studied as functions of surface pressure, induced by loads and pattern densities applied. For both materials, the wear rate was found to diminish with increasing surface pressure and the wear mechanism to resemble extrusion, producing flake-like particles. Dynamic friction levels were found to correlate with surface pressure, the micro-pattern having a distinct effect on friction with low loads. Both POM and PP were found to possess a friction minimum in the surface pressure range of 0.5-1.0 MPa, which is attainable by adjusting either the used load or the density of micro-patterns.