Effect of dispersion condition of calcium carbonate on the crystallization and melting behavior of polypropylene/CaCO3 nanocomposites

Polypropylene/calcium carbonate (PP/CaCO3) nanocomposites were prepared by melt compounding (C-1) and novel compounding process (C-2), respectively. Scanning electronic microscope (SEM) results illustrated that CaCO3 nanoparticles were well dispersed at nanoscale in C-2, whereas the nanoparticles were mostly aggregate in C-1. Differential scanning calorimetry (DSC) measurements indicated the onset crystallization temperature was increased by 11.4 degrees C and the supercooling wasdecreased by 13.68 degrees C in C-2. A faster crystallization rate, a higher melting point, and a higher degree of crystallization in C-2 were also detected. Polarization light microscope (PLM) photographs showed the spherulites sizes of C-2 were 60mm, whereas common spherulites with an average size of about 200mm were observed in both pure PP and C-1. These phenomena demonstrated that the well-dispersed CaCO3 nanoparticles could result in heterogeneous nucleation effect on PP even at quite low loading Q2 (1.5%wt.).