Effect of Sodium Lignosulfonate Treatment on the Dispersion of CaCO3 in CaCo3/Polypropylene Composite

The dispersion of calcium carbonate (CaCO3) in polypropylene (PP) and the effect of CaCO3 size on the crystallinity of PP were studied. Polymer composite usually suffers from the brittleness when reinforced with inorganic fillers. The problem is generally related to the size and dispersion of fillers. First, the dispersion was studied for the nanosize CaCO3 with 15 similar to 40 nm average diameter. To enhance the dispersibility in PP, the surface of the CaCO3 was treated with sodium lignosulfonate (SLS). CaCO3/PP composites were prepared via melt compounding. The CaCO3 coated with more than 3 wt% SLS was uniformly distributed within the PP matrix, while the uncoated CaCO3 formed aggregated structures in the PP. Even with 30 wt%, the SLS-CaCO3 was well dispersed in the PP matrix. Also, the transition enthalpy of CaCO3/PP increased and the full-width of half maximum of the crystallization peak decreased regardless of SLS coating and size of CaCO3. However, the crystallinity of PP was more influenced by nano CaCO3. These results imply that the nano CaCO3 coated with SLS may reduce the brittleness of polymer composites.