Preparation and characterization of Polypropylene/calcium carbonate nanocomposites: morphological analysis, mechanical properties and micromechanical deformations

Phase morphology, mechanical characteristics and deformation mechanisms of polypropylene (PP) reinforced by CaCO3 nanoparticles were studied. A homogeneous dispersion of CaCO3 nanoparticles up to 10 wt% in the PP matrix was observed via morphological analysis for PP/CaCO3 nanocomposites. Under tensile testing, the Young’s modulus gradually increased, while the yield stress progressively decreased with nanoparticles content. The ultimate strength was unaffected at initial concentrations of the nanoparticles and lowered at higher loadings of nanofiller. The strain at break increased at first but reduced at higher loadings of CaCO3 nanoparticles. The impact fracture energy of the nanocomposites improved with nanofiller concentration. The changes in mechanical properties with nanofiller content were rationalized by investigating the dispersion state of the nanoparticles in the nanocomposite and evaluating their interfacial adhesion with the matrix material, both of which were found to be controlled by nanofiller concentration as evidenced by microscopic analysis and theoretical models. The micromechanical deformation processes under the uniaxial tension and Izod impact loadings were determined by fractographic analysis. The impact-fractured surfaces of different samples was closely examined to elucidate the toughening (sub)micro-mechanisms operating in the nanocomposites.

Keywords:

Calcium carbonate nanoparticles , Morphology , Mechanical properties , Impact toughness , Deformation