INVESTIGATION IN THE USE OF COWPEA CHAFF AS AN ADDITIVE FOR NATURAL RUBBER.

Abstract

Natural rubber is a gummy liquid obtained from the sap fluid of the tree Hevea brasilensis. It is a natural hydrocarbon polymer of 2-methyl-1-3-butadiene (isoprene), which contains one double bond per repeating unit, whose structural arrangement typifies that of a cis-isomer (cis-polyisoprene). Natural rubber in its raw gum state is tacky, fairly elastic but suffers some limitations such as poor resistance to weathering condition, low tensile strength and hence additives are always added to improve on the limitations of the natural Rubber. Most additives are imported hence constituting additional cost. Cowpea chaff was used in this study as one of the additives. The cowpea chaff was chosen for this research due to its availability and cost since it is a waste material and expected to reduce cost of production. The cowpea chaff was grinded and sieved to fine particles (powder) using 100µm. The cowpea chaff powder was divided into portions and part were modified via nitration. The modified and unmodified cowpea chaff powder were characterized to determine the Ash content, Moisture content, Volatile content, pH, Loss on ignition, X-ray florescence (XRF) analysis was carried out to ascertain the elemental composition and Infra-red spectroscopy (FT-IR) to determine the functional groups and extent of the reaction of the samples. Each of the portions were compounded with Natural Rubber (NR) using calcium carbonate as control. The physico-mechanical properties of the vulcanizates obtained were determined. The study showed that chemically modified and unmodified cowpea chaff powders were good additives (softeners). Based on the parameters tested, it can be concluded that cowpea chaff can be substituted with CaCO3 filler in NR vulcanizates.