Mechanical and Surface Properties of E-beam Irradiated Polytetrafluoroethylene-Silicone Rubber Composites

Abstract

Compounding electron beam irradiated polytetrafluoroethylene (PTFE or Teflon) powder with silicone rubber produced silicone rubber/PTFE composites with desired physical properties. PTFE powder was exposed to electron beam irradiation at various doses and characterized by FTIR, DSC and contact angle measurements. Irradiation of PTFE with high energy electron beam induced chain scission reactions. Irradiated PTFE showed higher degree of crystallization and lower melting point with increasing absorbed dose. Number average molecular weight of irradiated PTFE was reduced significantly at higher absorbed doses. Formation of polar groups on the surface of irradiated PTFE powder was detected by FTIR spectroscopy. The latter was also verified by measurements of water-drop contact angle, which decreased with increasing absorbed dose. Mechanical and surface properties of the composites of silicone rubber and PTFE were characterized by tensile strength, abrasion resistance and water drop contact angle measurements. All the composites containing 5–15 phr PTFE showed higher tensile strength compared to the silicone rubber. Irradiation of PTFE powder had a significant effect on improving the abrasion resistance of the silicone rubber upon addition of only 5 phr irradiated PTFE. Similar abrasion resistance was obtained with the addition of higher amounts of non-irradiated PTFE (15 phr). Water drop contact angle of the composites decreased slightly with increasing the absorbed dose of PTFE.