Studies on EPDM/NR blends. I. Dielectric and mechanical properties

Ethylene-propylene-diene terpolymer rubber/natural rubber blends (EPDM/NR) in different proportions (100 :0, 75 : 25, 50 : 50, 25 : 75, and 0: 100) re inforced with 20 phr semireinforcing furnace carbon black have been studied . The permittivity epsilon' and dielectric loss epsilon" for these samples were determined in the frequency range 10(2)-10(7) Hz. Also, their physico- mechanical properties were investigated. The EPDM/NR blend (75 : 25) possessed the best mechanical properties and st ability against aging. Thus, it was chosen to explore the effect of adding carbon black in different quantities up to 50 phr on its electrical and mec hanical properties. Three different types of carbon black, namely high-abra sion furnace black, fast-extrusion furnace black, and medium thermal black, were used. At a certain concentration of carbon black, referred to as the threshold percolation concentration, an abrupt increase in epsilon' and eps ilon", which depends on its type, was detected. This could be attributed to some sort of interaction between the blend and the carbon black at higher concentrations.