Dynamic Rheological Behavior of Isotactic Polypropylene Filled With Nano-Calcium Carbonate Modified by Stearic Acid Coating

2 wt% and 6 wt% stearic acid (SA)-coated calcium carbonate (CaCO3) nanoparticles were compounded with isotactic polypropylene (iPP). Small-amplitude oscillatory shear tests were used to study the linear viscoelastic properties of the nanocomposite melts. The filler loading at which the composites exhibited the terminal modulus plateau was found to be much lower in the 6 wt% SA-coated particle composites than in the 2 wt% counterpart, and at the same filler content, apparently higher dynamic moduli and complex viscosities at low frequencies were shown in the former. The characteristics of pseudo-solid-like behavior almost disappeared in the 2 wt% SA-coated particle composites as the gap distance increased but were still observed in the 6 wt% counterpart. The results indicate that the dispersion of nanoparticles played a critical role in the motion of the macromolecular chains. At the same filler loading, the mobility of the iPP melts was more severely restricted by properly coated and well-dispersed nanoparticles than by aggregates due to insufficient coating.