THE USE OF COCONUT SHELL AS AN ADDITIVE IN NATURAL RUBBER COMPOUNDING.

Abstract

Coconut shells were collected and modified by drying in the sun, then milled to fine powder and sieved through a mesh size of 106 µm. Part of  the shells were carbonized while the remaining uncarbonized parts were retained for use. The carbonized and uncarbonized shells were characterized to determine moisture content, ash content, loss on ignition and pH. X-ray fluorescence (XRF) was carried out to determine the nature and abundance of the elemental constituents present. The loss on ignition values obtained for carbonized coconut shell (77.40%) were found to be higher than uncarbonized coconut shell (40.45%), which gave an indication of the carbon content in the material. The XRF analysis showed that the carbonized coconut shell (CCS) had higher concentration of carbon (59.0700 wt.%) than the uncarbonized coconut shell (UCS) (30.0301 wt.%). The resulting carbonized and uncarbonized samples were used as additive in the compounding of natural rubber by gradually replacing carbon black with each of these new materials at various ratios of 0, 5, 10, 20, 30, 40, 50, and 100% of carbon black. The resulting vulcanizates were then subjected to physico-mechanical and solvent resistance tests. The result of the physico-mechanical properties indicated that as the ratio of the coconut shell increases, the physico-mechanical properties decreases. For example, the result of tensile strength (MPa) of CCS at various ratios 5%, 10%, 20%, 30%, 40%, 50% and 100% were 12.90, 11.24, 10.90, 9.43, 8.54, 7.92 and 7.04 Mpa respectively. The results of the swelling and solubility showed that ethanol swells the vulcanizates more and faster than petrol, which was faster than kerosene and was also faster than diesel. The results obtained showed that vulcanizates with carbonized CS samples have better physico-mechanical properties than the uncarbonized vulcanizates due to higher carbon content. Vulcanizates with carbonized CS samples also show greater resistance to all the solvents as compared to the uncarbonized vulcanizates. Hence, CCS were much better than the UCS, but not as reinforcing as carbon black.