Morphology and properties of polypropylene/nano-CaCO3 composites prepared by supercritical carbon dioxide-assisted extrusion
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Polypropylene (PP)/calcium carbonate nanoparticles (nano-CaCO3) composites were prepared using a two-stage modular extruder with the assistance of supercritical carbon dioxide (sc-CO2). The crystallization and melting behavior, crystal forms, and crystal morphology were investigated by differential scanning calorimetry, wide-angle X-ray diffraction, and polarized optical microscopy. The loading of sc-CO2 injected into the extruder was optimized to be 2.0 phr. At this optimized loading, nano-CaCO3 particles were homogeneously dispersed in PP matrix. The addition of nano-CaCO3 particles has little impact on the melting behavior of PP, but exerts significant influence on the crystalline morphology of PP/nano-CaCO3 composites. At the optimized loading of sc-CO2, the PP/nano-CaCO3 composite has the highest impact strength due to the best dispersion of nano-CaCO3 particles in the PP matrix.
KeywordsImpact Strength Supercritical Carbon Dioxide Polarize Optical Microscope Dispersion Degree High Impact Strength
The authors are grateful to the Fund Project for Scientific Research of Young Teachers of Beijing Technology and Business University (QNJJ2011-32) for its financial support of this work, and also express their special thanks to associate professor Song Hong from Beijing University of Chemical Technology for his technical support with TEM and to professor Jian Yu from Tsinghua University for his valuable help and suggestions.
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