Influence of calcium carbonate and carbon nanotubes on the crystallization kinetics of polypropylene at high supercooling

Polymer fillers have been classified as active or inactive regarding their nucleation performance. Whereas an active filler significantly accelerates the crystallization process, an inactive filler has a significantly reduced influence on the crystallization kinetics. The majority of the studies of the filler influence on the crystallization process are performed at relatively low supercooling or at low cooling rates. In this paper, we use the Fast Scanning DSC to study the crystallization process of differently filled polypropylene (PP) in the temperature range between 120 °C and 0 °C. The inactive filler calcium carbonate reduces the crystallization rate of the α-phase at low supercooling (above 80 °C). Between 45 °C and 80 °C, calcium carbonate significantly accelerates the α-phase crystallization of PP. The mesophase crystallization is not affected by this filler. As an example of active filler, carbon nanotubes are used. Even with small filler content the α-phase crystallization of PP is significantly accelerated. Also in this case the mesophase crystallization is not significantly affected.