Influence of filler particle shape on elastic moduli of PP/CaCO3 and PP/Mg(OH)2 composites

The effects of filler particle shape on the Young's and shear moduli of PP/CaCO₃ and PP/Mg(OH)₂ composites were studied in the concentration interval up to 50 vol/vol % filler. Calcium carbonate had irregular, approximately spherical particles and magnesium hydroxide had particles either in the form of hexagonal plates or micro-needles. The analysis based on the classical models together with structural observations enabled explanation of the composition dependences of elastic moduli of the blends studied. It was found that immobilization of PP matrix on the filler surface prominently influenced the values ofG′ andE′ moduli of PP/CaCO₃ and PP/Mg(OH)₂ composites. The presence of the strongly immobilized PP with increasing geometrical anisotropy of the filler particles enabled a hyperstructure creation in the composites PP/Mg(OH)₂.