How does an increase in temperature affect the friction coefficient of a polymer-based material compared to a metal-based material?

When a polymer heats up, its molecules move faster and the material softens, so the surface becomes more compliant and the friction coefficient typically drops. In contrast, a metal’s structure is largely unchanged by moderate temperature rises, so its friction coefficient stays almost constant or may even rise slightly because of surface oxidation or changes in the thin oxide layer. The key idea is that polymers lose stiffness with temperature, reducing resistance, while metals maintain rigidity. For example, a rubber pad on a conveyor belt will slide more easily at 80 °C than at 20 °C, whereas a steel roller’s grip changes little over the same range. Thus, temperature increases usually lower friction for polymers but leave metal friction largely unaffected.