Effect of silver coating on electrical properties of sisal fibre-epoxy composites

In this paper, the effect of silver coating and size of fibre on electrical properties of sisal fibre-reinforced epoxy composites has been reported. For this purpose, epoxy composites reinforced with silver-coated sisal (of 5 and 10 mm length) prepared by hand moulding and samples were characterized for their electrical properties, such as dielectric constant (epsilon'), dielectric dissipation factor (tan delta) and AC conductivity (sigma (ac)), at different temperatures and frequencies. It was observed that dielectric constant increases with increase in temperature and decreases with increase in frequency from 500 Hz to 5 kHz. The peak height at the transition temperature decreases with increasing frequency. Interestingly, sample having silver-coated fibre of 5 mm length exhibited higher value of dielectric constant as compared to the sample having 10 mm of fibre length, which is attributed to the increased surface area of coated fibre. This behaviour of the material can be explained in terms of interfacial polarization. At a constant volume of fibres and at a length of 5 mm, the number of interfaces per unit volume element is high and this results in high interfacial polarization. The number of interfaces decreases as the fibre length increases and therefore the value of epsilon' decreases at 10 mm fibre length. To study the changes in structure of samples, Fourier transform infrared spectrometry and scanning electron microscopy of the samples were carried out.