Commercial stearic acid treated calcium carbonate (CaCO 3 ) was used to make a comparative study on rheological behavior of the CaCO 3 and talc-filled polypropylene (PP) hybrid composites with nontreated filler. Apparent shear viscosity and extrudate swell were investigated with variation of filler ratio and temperature with 30% by weight total of filler was used in PP composite. The Shimadzu capillary rheometer was used to evaluate shear viscosity and shear rate of the composite. It was found that the shear viscosities decrease with increasing shear rate. The apparent shear viscosity of the composite containing the stearic acid treated is slightly lower than untreated filler. Shear thickening behavior at higher shear rate has also shown by 15/15 treated composites at higher temperature about 2208C and investigation by SEM has proved that filler being densely packed at that condition. Treated composites also exhibit lower swelling ratio value than untreated composite, and swelling ratio also decreases linearly with increasing temperature and the die length-diameter ratio. It is believed that dispersion of filler play an important role not only on shear viscosity but also on swelling ratio of PP composite.

Abstract. The mineral and elemental composition, crystal structure and particle size distribution of kaolin clays have been determined to ascertain its industrial significance. The mineral composition is evaluated by X-Ray Fluorescence (XRF), crystalline structure by X-Ray Diffraction (XRD) and particle size distribution using low angle laser light scattering (LALLS) technique. The results shows the presence of eight elements expressed in percentages in form of their oxides as: SiO 2, Al 2 O 3, Fe 2 O 3, MgO, CaO, K 2 O, TiO 2 and P 2 O 5. Five crystalline structures are revealed by XRD result. The particle size distribution shows that kaolin particles are mainly in the range of 25-35 µm, while few particles have size distribution varied between 0.4-0.75 μm. The report is found to be in agreement with other researchers.

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All of the composites were prepared using Brabender internal mixer (50 rpm, 1908C) and molded using compression mold (1908C) to form test samples. The results showed that the tendency of kaolin particles to agglomerate was too strong, resulting in low strength and rigidity but fairly good toughness. To overcome the kaolin agglomerations dilemma, quaternary ammonium compound (QAC), sodium hexametaphosphate (SHMP), sodium hydroxide (NaOH), and polypropylene (PP) grafted maleic anhydride (PPgMAH) surface treatment agents were applied. Better dispersion of kaolin fillers were obtained with reduced size of the agglomerates. It was also found that nonreactive treatments enhanced the toughness of the composite remarkably, because of the softening effect that promotes plastic deformations. QAC was found to be the most effective dispersing agent of kaolin in PP matrix and contributes to 47% increment in the impact strength value compared to the untreated kaolin composite. QAC-treated kaolin also shows the most remarkable increment in melt flow index (MFI) and degree of crystallization (DOC) beyond other composites. To improve the dispersion and affinity of kaolin fillers to PP matrix, the processing enhancement was conducted at the end of the experiment.

The compound of single-component filled polypropylene (PP) (consists of either talc or CaCO 3 ) and multicomponent filled PP (talc/CaCO 3 /PP) are prepared by melt mixing using Brabender Plasticorder internal mixer. All systems exhibit good stability and normal flow in the molten state. The multicomponent filled PP has shown an intermediate degree of die swell and flow instabilities. The defect of extrudate in the extrusion process in the form of melt fracture could only be evidenced in the semisolid state of PP melt. The result shows that composite with highest content of talc exhibits the least melt fracture.