Comparison of the Morphology and Mechanical Properties of Unmodified and Surface-Modified Nanosized Calcium Carbonate in a Polypropylene Matrix

Polypropylene-(PP)-based nanocomposites with unmodified and surface-modified nanosized calcium carbonate (CaCO(3)) were melt-compounded to 3, 6, and 9 wt% filler contents. The nanofillers comprised two commercial grades from Mineral Technologies and one noncommercial pilot grade, and they differed in their particle size and/or surface modification. The fillers' dispersion and particle size and their adhesion to the matrix were examined by scanning electron microscopy. In addition, nanocomposite mechanical properties were determined and then compared with the properties of neat matrix material. Thermogravimetric analysis and differential scanning calorimetry were performed to determine the stearic acid content in the surface-modified fillers and their thermal stability. Microscopic examination revealed that the commercial grades dispersed better in and adhered more strongly to the matrix than the pilot grade. Thermal analysis showed that the commercial grade contained less stearic acid and was thermally more stable. Better dispersion, smaller particle size distribution, and less stearic acid seemed to result in balanced mechanical performance. POLYM. COMPOS., 32:464-471, 2011. (C) 2011 Society of Plastics Engineers