Flow Behaviour And Viscoelasticity Of Polypropylene-Kaolin Composites
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Date
2010-05
Authors
Abdul Rahim, Nor Azura
Journal Title
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Publisher
Universiti Sains Malaysia
Abstract
Melt flow and viscoelastic behaviour of polypropylene kaolin (PP-kaolin) composites were investigated using a single screw extruder at various filler loading, temperature, extrusion cycle and die diameter. It was discovered that for the effect of filler loading, 5 wt% of kaolin loading has caused MFI value and apparent viscosity of the composites to be slightly reduced with respect to pure PP. Whereas, above 5 wt% of kaolin loading the apparent viscosity started to increase. Experimental results also showed that swelling ratio and MFI decreased gradually with increasing amount of filler loading but unexpectedly at 30wt% of kaolin loading, the swelling ratio started to increase proportionately with shear rate. This was attributed to the void formation in between the cross-sectional area of the extrudates. Meanwhile, investigation for the effect of temperature, has proven that MFI increased while apparent viscosity and swelling ratio are reduced with temperature increment. It was also observed that a decrease in processing temperatures may caused significant bubble-like surface morphology. In the degradation studies, the results indicated that increase in processing temperature led to molecular chain scission of the polymer segment. However, a reverse trend of results was detected for the effect of extrusion cycle which indicated that the polymer chain segment are more prone to crosslink rather than chain scission with increasing number of extrusion cycles. Meanwhile for the determination of the true viscosity using different die geometry, it was found that the true viscosity is lower than the apparent viscosity after the Bagley and Rabinowitsch corrections were done. Later using the obtained apparent and generated true viscosity data, a cadmouldĀ® simulation was performed on a Computer Aided Simulation (CAD) dumbell model to determine the filling and shear stress analysis. The results has showed that, high-viscosity apparent viscosity data has substantially reduce the mould filling temperature, pressure, melt shear stress and increase the melt velocity during mould filling due extra heat generation from viscous dissipation effect compared to the true viscosity data.
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Keywords
Flow behaviour and viscoelasticity of , polypropylene-kaolin composites