Interrelationships between electrical and mechanical properties of a carbon black-filled ethylene-octene elastomer

The mechanical and dc electrical properties of a carbon black-filled ethyle ne-octene elastomer (EO) are reported. The stress-strain curves of the comp osites, scaled with that of the unfilled polymer up to approximately 500% s train, suggest good filler-matrix adhesion. The large reinforcement effect of the filler followed the Guth model for non-spherical particles. Electric al behavior under large strain was divided in four qualitatively or quantit atively different regimes that differentiated carbon black composites with the EO matrix from carbon black composites with chemically vulcanized matri ces. Among the most notable features of the EO composites was the completel y reversible variation of the resistivity, up to 20% strain, suggesting tha t these materials might be useful as strain gauges. In addition, depending on the carbon black content, the composites retained low resistivity to hig h strains. From the results of various thermo-mechanical treatments, a micr ostructural model for the response to stretching was proposed. This model i ncorporated dynamic junctions specific to the EO matrix to describe the mec hanical properties, the decrease in resistivity at low strains (20%), and t he weak increase in resistivity at intermediate strains (up to about 300%). (C) 2000 Elsevier Science Ltd. All rights reserved.