Fabrication and determination of mechanical and thermal properties of sisal/cattail fibre reinforced polyester hybrid composites

Abstract

Due to global environmental pollution and high energy consumption, researchers have been stimulated to seek for sustainable materials that can replace non-biodegradable and environmentally unfriendly materials in reinforced composites. Natural fibre- reinforcements seem to be good alternatives since they are biodegradable, abundant, inexpensive and have excellent physical and insulation properties and high strength to weight ratio. Therefore, sisal and cattail fibres provide a better alternative. Kenya produces about 25,310 tons of sisal fibres annually. Furthermore, cattail plant (Typha angustifolia) is a common marginal weed in Kenyan wetlands. The aim of this work was to fabricate a fibre reinforced polyester hybrid composite from a blend of cattail and sisal fibres (alkali treated and untreated), to investigate the properties of these fibres and the effects of varying the ratios on the mechanical and thermal properties of the hybrid composites. The percentages of cattail and sisal fibres in the blend were varied from 0- 100% (100/0,75/25,50/50,25/75,0/100) and moulded into hybrid composites using hand lay-up technique. Curing was carried out for 6 hours at room temperature under a pressure of 3.27kN/m 2 . The hybrid fibre weight fraction (wt.%) and cattail/sisal blend ratio were varied in order to determine their effects on the mechanical and thermal properties of the hybrid composites. Alkali treatment of the resultant composite was done by soaking some fibres in 4%w/v NaOH solution (sisal) and 5%w/v NaOH solution (cattail) for one hour at room temperature. Test specimens were prepared according to ASTM D638, ASTM D3410, ASTM D790, ISO 179 and ASTM C518 standards. Tenacity of treated sisal (146.26cN/tex) and cattail (35.35cN/tex) fibres was higher than that of untreated sisal (23.52cN/tex) and cattail (9.46cN/tex) fibres, while the linear density of treated sisal (10tex) and cattail (12.33tex) fibres were lower than 26.17tex and 35.17tex for the untreated fibres respectively. The flexural, tensile and compressive strengths of the hybrid composites increased as the proportion of sisal fibres was increased from 0-75% giving peak values of 45.97MPa, 32.39MPa and 25.43MPa respectively. Impact strength increased as the percentage of sisal fibres in the hybrid was increased from 0-100% to attain a maximum value of 34.40kJ/m 2 . Composites fabricated with alkali-treated fibres had better strengths (tensile-33.82MPa, flexural-45.68MPa, compressive-24.98MPa and impact-27.08kJ/m 2 ) than those fabricated with untreated fibres (28.89MPa, 36.65MPa, 21.05MPa and 23.19kJ/m 2 respectively). Cattail/polyester composites showed lower thermal conductivity (0.31W/mK) compared to 0.56W/mK for sisal/polyester composites. The mechanical and thermal properties recorded in this study indicate that these hybrid composites may be used for non-structural applications (as ceiling boards, walls, room partitioning, door panels and electronic and food packaging). However, further studies on their physical properties such as water absorption and flammability tests are required