Mechanical and electrical properties of alumina/natural rubber composites

Abstract

The mechanical and electrical properties of natural rubber (STR 5L)/alumina (Al2O3) composites with dicumyl peroxide (DCP) functioning as the crosslinking agent and as the filler in the composites were investigated. SEM micrographs indicate that the alumina particles are moderately dispersed in the matrix and some thread-like structures form. Both dicumyl peroxide and the alumina particles act the bi-dispersed particles in the composites. The XRD patterns indicate that Al2O3 is of the β-phase polytype that possesses high ionic conductivity. The electrical conductivity of the composites with DCP loading increases by nearly two and three orders of magnitude, compared to those of the STR 5L/Al2O3 composite without DCP and the pristine natural rubber (STR 5L), respectively. The increase in the electrical conductivity originates from the strong C–C and the Al–O–C bonds, the ionic polarization of the alumina particles, and the induced dipole moments set up in the natural rubber matrix.