Comparative Study of Dielectric Properties of Hybrid Natural Fiber Composites

The dielectric properties, such as dielectric constant, dissipation factor and dielectric loss factor of jute/bamboo natural fibers reinforced with polypropylene and unsaturated polyester hybrid composites were studied with different fiber loadings, fiber ratios, frequencies and chemical modifications of natural fibers. The dielectric constant, dissipation factor and loss factor increased with an increase in the fiber content for the entire range of frequencies than the pure polypropylene and pure unsaturated polyester materials. This increase was high at low frequencies, low at medium frequencies, and very low at high frequencies. Dielectric constant values were observed to decrease in frequency due to the decreased interfacial and orientation polarization at higher frequencies. Whereas, dielectric constant increased with an increase in the fiber loading, due to the increase in the number of polar groups, after the addition of hydrophilic lignocellulose fibers. Sodium hydroxide treatment was carried out on jute and bamboo fibers to improve the adhesion between fibers and matrix. The dielectric constant was lower for composites consisting of fibers subjected to alkaline treatment due to the increased hydrophobicity of fibers. When the weight percentage of jute fiber was increased in the total fiber content of the hybrid composites, the dielectric constant, dissipation factor and loss factor were found to increase. It is evident that types of polymer have little influence on the dielectric properties of the hybrid composites.