Mechanical, morphological, thermal, and durability properties of resin transfer moulded kenaf fibre reinforced unsaturated polyester composites
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Date
2016-06-01
Authors
Dody Ariawan
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Abstract
In the present study, the properties of nonwoven kenaf fibre (KF) mat /unsaturated polyester composites manufactured by resin transfer moulding (RTM) were investigated. Nonwoven KF mats were prepared by the alkali treatment and heat treatment for different time of treatment. The alkali treatment resulted in the partial removal of hemicellulose and lignin as evident from the results of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). Meanwhile, the heat treatment only removed impurities and extractives. These resulted in the increase of the adhesion properties and the fibre strength as well as the interlaminar shear strength (ILSS), tensile and flexural strength of composites, nevertheless alkali treated KF composites showed better mechanical properties than the heat treated KF composites. The optimum properties of alkali treated KF were obtained when KF was soaked in 6% NaOH solution for 3 hours. As for heat treated KF, the optimum properties were observed when KF was heat treated at 140oC for 10 hours. The experimental results of both untreated and treated KF mat composites were in line results with the results of micromechanic models. DMA results showed that both KF treatment resulted in a significant enhancement in the storage modulus (E’) and the glass transition temperature (Tg) of the composites samples. The Tg values of the composites were in the range of 81oC-85oC. In hygrothermal ageing investigation, the water uptake trend of composite samples at room temperature was found to follow the Fickian behaviour, whilst hygrothermal at 60oC and 90oC exhibited pseudo-Fickian behaviour. Alkali treated KF composites showed the lowest water uptake and superior flexural properties than heat treated KF composites. Moisture absorption promoted the degradation of composite samples, particularly at elevated temperatures and the mechanical properties could not be restored by subsequent drying. Nonwoven KF mat reinforced unsaturated polyester resin composites were exposed to a natural weathering environment for 12 months. This natural weathering was found to reduce flexural and fracture toughness due to the damage in composite structures, formation of void/micro cracks on the sample surface, discolouration and chemical composition alteration. Alkali treated KF composites relatively showed better durability with the respect to the retention of the mechanical properties than heat treated KF composites.