CaCO3 is one of the most commonly used fillers in thermoplastics, especially polyolefins. It is inexpensive and can be used at high loadings. Originally used as a cheap extender, fine grades of precipitated CaCO3 is now being produced in nanometer size and this nano precipitated CaCO3 (NPCC) has the potential to be an important functional filler in polypropylene composites [9–12]. The surface of the NPCC filler is usually treated with fatty acids such as stearic acid, to modify the filler surface to become hydrophobic. The main purpose for this surface coating is to reduce moisture absorption and hence particle agglomeration during storage, as well as to improve dispersibility of the polar filler when incorporated into non-polar polymer melts [13]. Improved dispersion of the nanofillers within the polymer matrix is a prerequisite for any improvement in mechanical properties, particularly impact strength.