Effects of thermal treatment on the tribological characteristics of thermoplastic polymer film

Friction tests were carried out using a microtribometer to investigate the effect of thermal treatment on microscale friction and wear between poly(methyl methacrylate) (PMMA) film and a fused silica lens. Two films were examined: one that was baked at 413 K for 2 min and one that was baked at 433 K for 24 h. The friction forces on the PMMA films were measured under atmospheric conditions as the temperature of the films was increased from 300 K to 443 K. The contact area between the films and the lens was also examined. As the temperature increased, the friction force increased for both films. The slope of the friction force with temperature and the contact area varied, depending on the state of the film surface; glassy, rubbery, and viscous flow states. The baking conditions also affected the slope, contact area, and wear generation. For temperatures at which the samples were in a glassy state, wear particles were not generated on the sample baked for 24 h. The results demonstrate that the tribological characteristics can be altered by the thermal treatment of the PMMA film as well as the temperature. When the film contains some residual solvent, the residual solvent in the PMMA film can diffuse to the PMMA surface due to heating and thus decrease the friction force under room-temperature conditions.