development and characterization of bio-composites from banana peels bio-resin, pseudo-stem banana and sisal fibres

Abstract

Composite materials result into lightweight structures with high stiffness and tailored properties for specific applications. Interest in agricultural materials for bio-composites has grown rapidly due to their renewability, biodegradability and eco-friendliness hence an alternative to non-renewable and non-biodegradable synthetic materials. Over 30 million tons of banana peels are thrown away annually worldwide, hence disposed of by burning that is environmentally unfriendly. Banana peels have a potential of development into eco- friendly resins for bio-composite production. Banana pseudo-stems are used for banana fibres though some are thrown away without further value addition. There is also a declining trend of sisal production worldwide due to competition from polypropylene synthetic fibres used in sack making, hence a decline in agricultural employment opportunities. Bio-composites from renewable resources therefore, will reduce waste disposal, promote agricultural value addition and create more employment opportunities. The objectives of this study were to develop, characterize and optimize bio-resin development from raw banana peels. Then surface-treat and characterize pseudo-stem banana and sisal fibres, followed by development, characterization and optimization of the design of bio-composites from banana peels bio-resin, pseudo-stem and sisal fibres. Pureed raw banana peels paste was mixed with various ratios of water and Glycerine at different temperatures and time and the bio-resin characterized for viscosity and density. Pseudo- stem banana and sisal fibres were treated with 4% sodium hydroxide, boiled at 100 0 C for 1 hour, dried under the sun and characterized. The fibres were chopped to a critical length of 15mm and bio-composites produced using the hand layup technique and characterized. Using surface response experimental design and regression analysis, effect of fibre volume fraction, bio-resin mass and Glycerine mass on the mechanical properties of the developed bio-composites were studied. The viscosity model exhibited an R 2 value of 0.95 and an optimum viscosity of 242 mPa.s. Percentage contributions of factors affecting viscosity of the bio-resin were water amount at 20% and Glycerine amount (18.6%) among others. Regression analysis for bio-resin density yielded an R 2 of 0.83 with an optimized density of 0.95g/cm 3 . Viscosity and density values were in close range with other commercial resins. Treated pseudo-stem banana fibres yielded a linear density of 12.52tex, elongation (0.49%), tenacity (189.5MPa) and Young’s modulus (3Gpa). Treated sisal fibres yielded a linear density of 23.84tex, elongation (1.03%), tenacity (217.13MPa) and Young’s modulus (5.6Gpa). There was significant improvement in the mechanical properties of treated pseudo-stem banana and sisal fibres than untreated fibres. Treated pseudo-stem banana and sisal fibres were used for bio-composite development using the optimized bio-resin. Sisal and banana bio-composites yielded tensile strengths of 5.2MPa and 4.2MPa respectively, with an R 2 value of 0.93 and fibre volume fraction contributing the highest percentage of 38.11% to the model. The sisal and banana bio-composites also exhibited compressive strengths of 2.9MPa and 2.1MPa respectively with an R 2 value of 0.92 and fibre volume fraction contributing the highest percentage of 42.8% to the model. The optimized bio- composites were comparable to the available commercial composite boards. The developed bio-resin can be used in development of bio-composites for interior applications including partition, ceiling and notice boards as an alternative to non-renewable and non- biodegradable petroleum based materials and solid wood products.