Physical and tribological properties of the modified PTFE nanopowder filled EPDM

INTRODUCTION Polytetrafluoroethylene (PTFE), a highly crystalline polymer with melting temperature around 330°C, possesses unique properties. Chemically inert, it has high chemical and heat resistance with upper service temperature around 260°C. Since its invention it has found limited applications especially as an additive because of its high molecular weight and inert surface. However, by mid 1950’s Crandell [1] used PTFE as a reinforcing additive to improve the tear strength of silicone rubbers while by late 60’s it was further used in fluoroelastomers [2-3]. For tribological purposes, PTFE and its fluoropolymers have found a wide use as a solid lubricant in applications such as bushings. Although, it has unique low friction characteristics, it suffers from high wear rate because of its smooth molecular structure [4]. For this reason, it is commonly used in conjunction with various kinds of fillers, thermoplastics and resins in order to exploit its inherent low friction characteristics and at the same time reduce its high wear rate behaviour [5-8]. Recently the development of chemically coupled PTFE compounds has opened a new route in producing enhanced wear resistant materials for high performance tribological applications [9-10]. In order expand its utility in technical elastomers, a new class of modified PTFE filled SBS, NBR and EPDM compounds were produced [11]. Modified PTFE micropowder were also incorporated in a carbon black filled NBR composition for sealing applications [12]. However, a comprehensive investigation based solely on the friction and wear mechanism of PTFE coupled elastomers along with their physical properties in the mentioned studies has not been reported so far. Our preliminary investigations conclude that electron beam irradiated PTFE nanopowder in EPDM enhances the physical properties [13]. However, the factors influencing the physical properties of the PTFE based EPDM might not hold true for their tribological properties. The effectiveness of the PTFE in EPDM on the tribological and physical properties of vulcanizates containing irradiated PTFE, non-irradiated PTFE and without PTFE in EPDM is discussed.