Rheological and mechanical properties of polypropylene/calcium carbonate nanocomposites prepared from masterbatch

Abstract

Polypropylene (PP)/calcium carbonate (CaCO3) nanocomposites were prepared from masterbatch by melt blending in a twin-screw extruder. The effect of three different nano-CaCO3 loadings (5, 10, and 15 wt%) on the rheological/viscoelastic and mechanical properties of the nanocomposites was investigated. A scanning electron microscopy was used to study the morphology of the nanocomposites, whereas a differential scanning calorimetry was used to analyze the thermal properties. The rheological properties were characterized using an oscillatory rheometer, and the mechanical properties were characterized by a tensile test machine. In the melt rheological study, a frequency sweep test showed that the complex viscosity [Formula: see text], the storage modulus ( G′), and the loss modulus ( G″) of the nanocomposites increased with nano-CaCO3 loading. The increase in [Formula: see text] was approximately 1.4–1.9 times greater than that of the PP matrix. Shear-thinning behavior was also observed for the nanocomposite samples. Additionally, the relaxation time spectrum and the relaxation modulus, G( t), were determined by fitting experimental data ( G′ and G″) using the Maxwell element method via numerical analysis. The results showed that the time required for stress relaxation of the nanocomposites was longer than that of the matrix. In the solid viscoelastic study, dynamic mechanical thermal analysis results showed that the G′ value of the nanocomposites increased by approximately 15–25% compared with that of neat PP. The tensile test results showed an improvement in the tensile modulus and toughness (especially at 10 and 15 wt%), while the tensile strength showed a moderate decrease. On the other hand, the incorporation of nano-CaCO3 in the PP matrix has enhanced the overall flexural and Izod impact properties of the nanocomposites.