Electrical conduction in thermoplastic elastomer matrix composites containing catalytic chemical vapour deposited carbon whisker
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Electrical conduction in carbon whisker/thermoplastic elastomer (TPE) composites was found to be a thermally activated process. The carbon whiskers used were obtained by a catalytic chemical vapour deposition (CCVD) technique conducted at 500 °C and the TPE was a styrene-ethylene butylene-styrene (S-EB-S) block copolymer. The resistivity, (ϱ), versus 1/T curves of the composites exhibited two regions with distinct slopes with an inflection at the glass transition temperature,Tg, of the elastomer, EB; Region I <Tg and II >Tg. The thermally activated conduction mechanism of these composites is explained on the basis of electron transport in low-mobility solids with a large number of trap sites, Intra- and intermolecular motion of the polymer chains can result in the electron transport from such trap sites and were correlated to the observed activation energies. Intramolecular motion in region I, was related to the thermally assisted hopping with the activation energy, ΔEA, of 0.067 and 0.030 eV for 33% and 52% whisker volume fraction composites, respectively. Similarly, ΔEA due to the intermolecular segmental chain motions in region II for 33% and 52% whisker volume fraction composites was related to the equilibrium rate of trapping-detrapping of electrons from 0.240 and 0.138 eV deep traps.
KeywordsActivation Energy Glass Transition Temperature Block Copolymer Conduction Mechanism Segmental Chain
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