Effect of surface treatments on the electrical properties of low-density polyethylene composites reinforced with short sisal fibers

The electrical properties of short-sisal-fiber-reinforced low-density polyethylene composites have been studied. Various surface treatments such ns alkali, CTDIC, stearic acid, peroxide, permanganate and acetylation were carried out on the sisal fibers to improve interfacial bonding. The treated surfaces were characterized by infra-red spectroscopy. The dielectric constant increases progressively with increase in fiber lending and decreases with increase in frequency for all composites. The dielectric constant values of the composites were found to have decreased as a result of chemical treatments. This is due to the fact that the hydrophilic nature of natural fiber decreases with treatment. Volume resistivity values of treated-sisal-fiber/LDPE composites were found to be greater than those of raw-sisal-fiber/LDPE composites. Volume resistivity values of permanganate-treated-sisal-fiber/LDPE composites depend on the concentration of KMnO4 solution used for treatment. The value of volume resistivity increases, reaches a maximum and then decreases with increase in concentration of potassium permanganate solution. The dielectric loss factors of treated-sisal-fiber-reinforced/LDPE composites were found to be lower than that of untreated-sisal-fiber/LDPE composites. The relaxation peak is found to be in the same region for all composites. (C) 1997 Elsevier Science Limited.