Tribological study of peroxide-cured EPDM rubber filled with electron beam irradiated PTFE powder

The aim of this work is the evaluation of the effects of electron beam modification of Polytetrafluoroethylene (PTFE) powder on the friction and wear properties of PTFE filled Ethylene-Propylene-Diene-Monomer (EPDM) rubber cured by a radical-initiated peroxide system. Friction and wear properties of EPDM vulcanizates were determined with the help of pin-on-disc tribometer in sliding contact with a steel-ball at room temperature without lubrication. PTFE powder was modified in atmospheric conditions with low (20 kGy) and high (500 kGy) irradiation doses using electron beam accelerator. The spectroscopic investigations reveal that the increasing concentration of reactive free radicals and functional groups with irradiation dose has a drastic influence on crosslinking efficiency due to their interference with peroxide radicals in curing process. As a result, non-irradiated and low-irradiated PTFE filled EPDM with higher crosslinking densities showed remarkably enhanced friction and wear properties. On the contrary, 500 kGy PTFE filled EPDM having significantly lower crosslinking density resulted in poor friction and wear characteristics. The apparent crosslinking density measured directly from the curing curves was found to be the most dominating parameter influencing friction, wear as well as the physical properties.