Sisal- formaldehyde crosslinked CNSL composites

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University of Dar es Salaam
Sisal fibre bundles have high tensile properties that can be used to reinforce polymer matrix in composite materials. However, the presence of surface impurities and their incompatibility to hydrophobic polar resins matrix necessitates for surface modification of the fibre or the resin. Alkalisation with sodium hydroxide was used in this study to chemically modify the surface of sisal fibre bundles in order to improve their compatibility with cashew nut shell liquid (CNSL)-formaldehyde cross linked resin matrix in the manufacture of composites. The sisal fibres bundles samples were alkalised with sodium hydroxide solutions concentrations 0.02 M, 0.04 M, 0.06 M, 0.08 M, 0.5 M, 1.0 M, 1.5 M, 2.0 M and 2.5 M, and analysed for physical, tensile, fine structure and thermal properties in order to determine alkaline concentration that would give optimal fibre properties. It was found that sisal fibre bundles treated with sodium hydroxide solution of concentration of 0.06 M had optimal mechanical and thermal properties. Unidirectional sisal-CNSL composites were manufactured by hand lay-up method using sisal fibres bundles alkalised with sodium hydroxide of various concentrations as above. The effects of alkalisation of the fibre bundles on the physical, thermal, mechanical and thermal-mechanical properties of sisal-CNSL composites were investigated. Sisal-CNSL composites made from sisal fibres bundles alkalised with sodium hydroxide of concentration 0.06 M was observed to produce composites with optimal physical, thermal, mechanical and thermal-mechanical properties. Furthermore, the specific strength and Young’s Modulus of this composite was found to be comparable to that of composites made with synthetics fibres and resins such as carbon-epoxy and glass-polyester composites. The results of this study indicates that renewable materials such as sisal fibre bundles and CNSL-based resin can be used in the manufacture of composites materials that could partially replace synthetic based materials such as carbon-epoxy or glass-polyester in light weight applications. The use of renewable materials in structural applications will contribute to environmental conservation through reduction of pollution associated with production of energy intensive synthetic materials.
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Sisal (fiber)
Msemwa, P. B (2013) Sisal- formaldehyde crosslinked CNSL composites, PhD dissertation, University of Dar es Salaam. (Available at