DEVELOPMENT OF SISAL FIBRE REINFORCED POLYPROPYLENE COMPOSITES SUITABLE FOR STRUCTURAL APPLICATIONS

Abstract

In recent years natural fibres appear to be the outstanding materials which come as the viable and abundant substitute for the expensive and non-renewable synthetic fibres. Natural fibres from pineapple, sisal, banana, jute, oil palm, kenaf and coir has been used as reinforcement in thermoplastic composite for applications in consumer goods, automobile, low cost housing and civil structures among others. It is the objective of the current research to extract sisal fibre by soil retting process and to investigate the effect of fibre treatment on the mechanical and water absorption properties of sisal fibre reinforced polypropylene (PP) composite. Two types of polypropylene, homopolymer and copolymer were used. Sisal fibre used for this research was extract by soil retting process. In order to modify the fibre surface for enhanced bonding at the fibre/matrix interface and as well prevent fungi attack, the fibre was chemically treated. Modification is necessary to improve the mechanical properties and to hinder moisture absorption. The fibre constituents after treatments were analysed and samples from both treated and untreated fibres were tested for tensile strength. The surface morphology of the fibres was later examined with SEM. Both treated and untreated fibre samples were further prepared by combing to remove scales and later oven treated at 70 ºC for 1 hour. Both PP and sisal fibre were compounded using compression moulding via hot press machine followed by grinding to reduce the fibre size to 8mm in length. Reinforced Polypropylene composites were produced by using the compression moulding machine to form tensile test samples and 150 mm X 100 mm X 3 mm for other tests to sizes. After forming, samples were prepared for tensile, hardness, flexural, Charpy impact and water absorption tests which were carried out in accordance with ISO / R 527, ISO R 868, ASTM D790, ISO 179 and ISO 175 respectively. Scanning Electron Microscope (SEM) was used to investigate the blending between the fibre and matrix at the fractured surfaces. The result obtained was also compared with previous work and, it was found that soil retting can be used for the extraction of sisal fibre due to the high tensile strength values that were obtained from both treated and untreated sisal fibres. The chemical treatments were found to be effective in enhancing the properties of the sisal fibre and sisal-PP composites. This was possible because of the removal of the deleterious constituents of the fibre, thereby, providing a good surface morphology for the fibre/matrix interface bonding as shown by the SEM. The study demonstrated that best results can be obtained by incorporating small amount of fibre into the matrix since fibre loading for the best performance of the composite was 3 wt%. The study also revealed that the properties of treated sisal-homopolymer matrix based composites were better enhanced compare to that of the copolymer matrix based composites. This was due to good blend obtained between the homopolymer and sisal fibre than that of the copolymer and sisal fibre as revealed by the SEM