Abstract. Tribological properties of Ethylene-Propylene-Diene-rubber (EPDM) containing electron modified Polytetrafluoroethylene (PTFE) have been investiagted with the help of pin on disk tribometer without lubrication for a testing time of 2 hrs in atmospheric conditions at a sliding speed and applied normal load of 0.05 m·s -1 and FN = 1 N, respectively. Radiation-induced chemical changes in electron modified PTFE powders were analyzed using Electron Spin Resonance (ESR) and Fourier Transform Infrared (FTIR) specroscopy to characterize the effects of compatibility and chemical coupling of modified PTFE powders with EPDM on mechanical, friction and wear properties. The composites showed different friction and wear behaviour due to unique morphology, dispersion behaviour and radiation functionalization of PTFE powders. In general, EPDM reinforced with electron modified PTFE powder demonstrated improvement both in mechanical and tribological properties. However, the enhanced compatibility of PTFE powder resulting from the specific chemical coupling of PTFE powder with EPDM has been found crucial for mechanical, friction and wear properties. Vol.3, No.1 (2009) [39][40][41][42][43][44][45][46][47][48] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2009.7 ene (PTFE) with its remarkably low friction coefficient has also gained interest for use in tribological applications [9][10][11][12]. In rubbers, PTFE was initially used as a reinforcing additive in Silicone and Fluorosilicone rubbers [13][14][15] and afterwards in Styrene-butadiene-rubber, Acrylonitrile-butadienerubber and Butyl rubber [16]. New PTFE-based rubber compounds and compounding procedures have been introduced in improving mechanical properties of both low-strength (ethylene propylene, silicone) and high-strength (nitrile) rubbers for O-rings, sealing and valves etc. [17]. However, PTFE especially in rubbers have not been achieved with any commercially significant success. This is mainly due to the intractability of PTFE in providing homogeneous formulation because of its poor wetting and dispersion characteristic. This problem results from the unique properties of PTFE, most probably its highly hydrophobic surface which resists wetting. There is indeed a strong motivation to investigate new techniques and procedures for the use of PTFE powder in rubber compound as solid lubricant for tribological applications. More recently, chemically coupled PTFE-polyamide [18] and PTFE-rubber [19] compounds based on the modification of PTFE powder by high energy electrons has opened a new way in producing materials for tribological applications. Radiation functionalization produces PTFE micropowders containing persistent trapped-radicals radicals and functional groups on the surface of PTFE powder can be easily compounded into elastomers such as EPDM rubber. A detailed characterization related to the mechanical, friction and wear properties of PTFE-based EPDM compounds have been presented by the authors in [20,21]. In previous attemp...