The role of internal friction in the process of energy dissipation during PTFE composite sliding against steel

The state of strain varies in a polymer material during sliding against steel. The reasons for this are, among other things, imperfections of shape of the surface of the contacting steel element and the oscillatory character of the friction force. The viscoelastic nature of polymer materials (considerable internal friction) means that under such conditions a certain amount of friction energy is dissipated in the form of heat inside these materials, contributing to their heating up. For this reason the internal friction for selected PTFE composites has been investigated, as well as the temperature distribution on the surface of PTFE samples sliding against steel under dry friction conditions. It was observed (using a thermovision system) that the highest temperature occurred inside the polymer material, at some distance from the friction surface. That testifies to the generation of heat during friction, not only on the contact surface of the sliding materials but also inside the polymer material. Both thermovision investigations and computations demonstrated the essential role that internal friction plays in polymer materials during their sliding against metals.