Melt behavior of polypropylene-co-ethylene composites filled with dual component of sago and kenaf natural filler

A dual component natural filler system featuring discrete function appears to be suitable for modulating smooth flow of pseudo-plastic into formulated biodegradable polymer composite. Polypropylene-co-ethylene (PPcoE) filled with sago starch and different kenaf powder loadings were compounded using co-rotating twin-screw extruder to produce dual component polymer composite. The flow characteristics of the composites were measured using capillary rheometer and Bagley corrections were performed to achieve the true rheological data. In addition, data collected from the twin-screw extruder were used to calculate the composite apparent rheological value. The flow properties of PPcoE filled with sago starch (PPcoE/sago) exhibited deviation from the common non-Newtonian thermoplastic flow paths at high shear rates. Interestingly, the addition of kenaf powder into the PPcoE/sago starch blend stabilized the melted composite flow stream. The calculation of interfacial tension revealed that the flow corrections were related to the phase selective localization of kenaf particle, which preferably embedded between the sago particles rather than in the surrounding PPcoE phase thus reducing the effect of sago clustering. At higher extrusion temperature, the extruded composite indicated sign of flow instability due to factors of high amount of kenaf powder loading and the degradation of sago starch and PPcoE chains.