Electrical properties of pineapple fibre reinforced polyethylene composites

Pineapple-fibre-reinforced, low-density polyethylene (LDPE) composites were prepared by a solution mixing-technique. The dielectric constant, volume resistivity, and dielectric loss factor of the composites were evaluated as a function of frequency, fibre content, and fibre length. The dielectric constant values were higher in the fibre-filled system than in pure LDPE. Dielectric constant values were found to increase with increased fibre loading because of the increase in polar groups after the addition of hydrophilic lignocellulosic fibres. Fibre treatments, such as isocyanate, silane, and peroxide treatments, were done to improve the adhesion between the fibre and LDPE matrix. We studied the influence of the chemical treatments on the electrical properties of the composites. The dielectric constant values were higher in the treated fibre composites than in the unmodified ones. The effect of fibre loading on the conductivity of the system was evaluated. A percolation threshold was obtained at 15% fibre loading. The respective estimated values of the filling factor and the effective coordination number were 0.061 and 8.1. The volume resistivity was found to be greater for chemically treated fibre composites. The electrical conductivity was decreased by chemical treatment of the fibres. A dielectric relaxation was observed at a frequency of 1 MHz.