Preparation of unidirectional polypropylene reinforced kenaf composite using mechanical impregnation method

Kenaf plant is one of the potential sources of natural fibre in Malaysia. Research in kenaf plastic composite is growing tremendously parallel to the high demand from the plastic industry which aiming to produce the natural fibre based materials. In this project, unidirectional kenaf fibres and polypropylene (PP) were used for manufacturing a composite. The composite was prepared by a new developed mechanical impregnation method. The mechanical impregnation technique involves transferring the PP into unidirectional kenaf fibre and controlling compression pressure given on the composite mould. The mechanical impregnation is composed by three parts; (1) compression moulding, which function to form the composite product by using identified mould, (2) a controlled speed barrel plunger, which is place to melt the polypropylene and transfer the melted polypropylene into unidirectional kenaf bundle, (3) a load cell, which is to determine the pressure given. Properties of PP were evaluated using melt flow index test (MFI) and viscosity determination. It was found that the MFI of polypropylene at optimum processing temperature 230°C is 36.7 g/10min. Besides that, PP also showed a zero viscosity behavior or η0 and a lower Newtonian region were observed at this temperature. PP/Kenaf composite was produced with the optimum processing parameters and mechanical properties were investigated according to tensile test and izod impact test. The thermal properties were determined by dynamic mechanical analysis (DMA) and the morphology of fracture surface was studied using scanning electron micrograph (SEM). The pressure is stable at 200 Kpa and the tensile strength of PP/Kenaf composite increased to 35.14 Mpa as compared to virgin PP with addition of 40% volume of kenaf fibre. However impact strength was decreased to 130.98 J/M. The dynamic mechanical properties of PP/Kenaf composites showed that the storage modulus (E’) and loss modulus (E”) decreases with increase in temperature. However, the storage modulus (E’) and loss modulus (E”) of PP/Kenaf composite was increased as compared to virgin PP. This finding showed that the addition of kenaf fibres in composite influenced the elasticity of PP. In addition, the tan δ properties were decreased because the relative damping peak height is affected by the concentration of the measured materials. It was also found that the glass transition temperature (Tg) of PP/Kenaf composite was shifted to the lower temperature at 14.7°C. From the scanning electron micrograph (SEM), it can be clearly seen that the PP is fully penetrated in the unidirectional kenaf fibre and this also illustrated the efficiency of mechanical impregnation process. However, the micrograph of impact test found that the fibre pull out and showed the fibre breakage behavior. These imply that, the preparation of unidirectional polypropylene reinforced kenaf composite using mechanical impregnation method will create opportunities to the small medium industry and fresh entrepreneur to increase the composite production by implementing a lower energy and lower cost for economic growth in Malaysia. Therefore, it will improve the smart materials production where only through this material the balance of the ecology can be maintained. Finally, the sources of resources can be diversifying according to the composite based industries, particularly in terms of natural fibre.

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