Abstract
The electrical resistance of carbon blak-filled rubber vulcanizates was measured under repeated elongations (and retractions) and stress relaxation. Also the changes of carbon black distribution due to elongation were observed with an electron microscope.
It was found that the electrical resistance of vulcanizates decreased under stress relaxation, but increased by repeated elongation.
It was found under an electron microscope that partial deformation occurred in the specimens on a scale of μ and the carbon black distribution became more heterogeneous under large elongation.
We supposed that the carbon black particles in the places where the contents of carbon black became higher under elongation may agglomerate and finally a very heterogeneous structure may appera after repeated elongations.
It was also found that the carbon black in SBR vulcanizate showed a different behavior from those in N R and BR.