MECHANICAL PROPERTIES AND WATER ABSORPTION BEHAVIOR OF NATURAL RUBBER FILLED WITH MELON HUSK AND SAWDUST

Abstract

Fillers are materials which when added to rubber mix enhance the properties. These properties are physical in nature which include hardness, tensile strength, flex fatigue, stiffness and to some extent, the chemical properties. Fillers improve the processing characteristics, reduce cost and also act as auxiliary components necessary for vulcanisate. In rubber industry, fillers that are commonly in use are carbon black, China clay and calcium carbonate. The process of producing carbon black requires tremendous energy utilization, heavy infrastructure setup and constitutes a heavy source of environmental pollution and it is also carcinogenic. Nowadays, there has been a growing interest in the use of individual and agricultural waste as fillers because of their renewability, low cost, readily available and environmental friendly. The mechanical properties and water absorption behavior of natural rubber filled with melon husk and sawdust as fillers were studied. The melon husk and sawdust were characterized in terms of moisture content (melon husk = 5.80% and sawdust = 9.80%), iodine absorption number (melon husk = 59.00 and sawdust = 70.40), pH (melon husk = 6.30 and sawdust = 6.40), particle size of the fillers were 75µm and compounding was done at varying filler loadings (10 to 40pphr) using two roll mill machine. The mechanical properties result showed that incorporation of melon husk and sawdust into the vulcanized natural rubber generally increased as filler loadings increased. The highest tensile strength (sawdust = 10.25-27.11 MPa and melon husk = 10.25-25.03 MPa), tensile modulus (sawdust = 1.68-3.04 MPa and melon husk = 1.68-2.35 MPa), hardness (sawdust = 35.03-48.06 IRHD and melon husk = 35.03-45.92 IRHD) and abrasion resistance (sawdust = 18.50-36.35% and melon husk = 18.50-30.13%) were obtained as filler loadings increased. The elongation at break (sawdust = 803-515% and melon husk = 803-560%), compression set (sawdust = 25.13-11.50% and melon husk = 25.13-12.75%) and flex fatigue (sawdust = 15.45-7.29 Kc x 103 and melon husk = 15.45-7.85 Kc x 103) of composites decreased as the filler loadings increased. The sawdust filled vulcanizates showed better mechanical properties than melon husk filled vulcanizates. In addition, the effects of these fillers on the end-use properties such as water absorption were examined. The results showed that as the filler loadings increased, the water uptake in melon husk filled vulcanizates and sawdust filled vulcanizates increased due to hydrophilic nature of the fillers. The sawdust filled vulcanizates had more water uptake than the melon husk filled vulcanizates.