Characterization of alkali-treated kenaf fibre-reinforced recycled polypropylene composites

In this study, composites were produced using alkali-treated kenaf fibre and recycled polypropylene to improve the interfacial bonding between them. Maleic anhydride grafted polypropylene was used at a ratio of 1: 10 to the fibre as a coupling agent. Blends are mixed together by means of a twin screw extruder and test specimens for mechanical testing were prepared through injection moulding machine. Fibre density, tensile property, elemental analysis, structural and morphological changes due to treatment was observed and their effects on the properties of the formulated composites were analyzed. Characterization of the composites was done by the tensile, flexural, impact and melt flow index tests. Thermogravimetric analysis and differential scanning calorimetry analysis were carried out to evaluate the thermal properties of the composites. Experiment showed that best tensile strength (TS) was found at 40% loading of fibre and alkali treatment of fibre enhanced the TS by 57%. Activation energies were calculated through Broido's equation. It was also found that recycled polypropylene degrades at one stage, while composites degrade at two stages. Incorporating fibres decrease the activation energies of the composites but both coupling agent and treatment of fibres in that case enhance activation energies by 11 kJ mol(-1) and 29 kJ mol(-1), respectively, in the second stage. Field emission scanning electron microscope of the fractured surface showed that treatment of fibre improves the interfacial bonding between fibres and matrix. Density and water uptake of the composites were also studied in this study.