EFFECT OF EXTENSIONAL STRAIN ON THE RESISTIVITY OF ELECTRICALLY CONDUCTIVE NITRILE-RUBBER COMPOSITES FILLED WITH CARBON FILLER

The resistivity and mechanical properties of nitrile-rubber based conductive composites filled with short carbon fibres (SCFs) and mixed filler system (SCF + carbon black) are studied as functions of the extensional strain and the strain rate. It has been observed that both strain and strain rate have a strong influence on the resistivity of the composites. The sensitivity of the change in resistivity against the strain and strain rate depends on the concentration as well as the type of conductive filler. SCFs impart higher conductivity to the composite than a blend of SCFs and carbon black at the same level of loading parts per hundred of rubber (p.h.r.). Composites filled with a mixed filler system show high mechanical properties in contrast to those of SCF-filled composites. The change in resistivity with the degree of strain is less pronounced in mixed-filler-filled composites than in only carbon-fibre-filled composites. The mechanical properties of the composites are dependent on the polymer-filler interaction whereas change in resistivity is dependent on the transient arrangement of the conducting components in the polymer matrix. A good correlation exists between mechanical and electrical response to the strain sensitivity.