Characterization and properties of stearic acid, titanate and zirconate modified dolomite/polypropylene composites

An increase in demand for the use of natural mineral filler polymer composites has attracted attention towards a greener environment and in reducing the processing and production cost of composites materials. In this study the effect of dolomite filler content and the effect of filler treatments on the mechanical, thermal and degradation behaviour of modified dolomite/polypropylene (PP/dolomite) composites were investigated. The first part of this study reported on the preliminary study on optimum ground dolomite properties. The raw dolomite was ground using various grinding time in order to obtain the optimum size of dolomite particle to be incorporated into the composites. The grinding process of 2h resulted in optimum grinding parameter with particle size 8.183m and maintained crystalline structure even after the intensive grinding operation in the planetary mill. Secondly, the PP/dolomite composites containing 0 – 25 wt.% of dolomite was prepared using Brabender internal mixer at temperature 180°C , rotor speed 60 rpm and compression moulding method. The addition of dolomite into the PP matrix decreased the tensile strength and elongation at break of the composites. The Young’s modulus increased due to the addition of dolomite particulate filler into the PP/dolomite composites. Thermogravimetric analysis (TGA) confirms that the addition of lower content of dolomite increased thermal stability of the composites. In the third part, the effect of stearic acid content as modifier on the surface treatment of PP/dolomite composites was studied. It was found that the dolomite has been successfully modified by the stearic acid observed through the fourier transform infrared (FTIR) and exhibited that the optimum stearic acid content has elevated the percentage of hydrophobicity and resulted in highest tensile strength, elongation at break, flexural properties and also thermal stability of the polymer composites. A better interfacial adhesion between the particulate dolomite and PP also was observed. This optimum stearic acid content obtained was then maintained in order to compare the effect of other modifiers which were titanate (LICA12) and zirconate (NZ12) as modifiers towards the mechanical, thermal and morphology behaviour of the composites. The addition of these modifiers has shown a significant improvement the tensile strength and Young’s modulus of the composites. The modified PP/dolomite composites showed slight improvement on tensile strength, impact strength and flexural properties. FTIR spectra proved the changes of functional group of modified dolomite and enhancement of interfacial adhesion respectively. The addition of nanosilica has marked an improvement in the impact strength of modified composites compared to unmodified ones, but on the other hands it lowers the thermal stability. The final part of this study focused on the effect of degradation by natural and accelerated weathering to the mechanical and physical properties of PP/dolomite and its hybrid nanocomposites. The composites of PP with modified dolomite sustain the tensile strength for both natural and accelerated weathering.