Plasticization of nano‐CaCO 3 in polystyrene/nano‐CaCO 3 composites

The shear rheological properties of polystyrene (PS)/nano‐CaCO 3 composites were studied to determine the plasticization of nano‐CaCO 3 to PS. The composites were prepared by melt extrusion. A poly(styrene–butadiene–styrene) triblock copolymer (SBS), a poly(styrene–isoprene–styrene) triblock copolymer (SIS), SBS‐grafted maleic anhydride (SBS–MAH), and SIS‐grafted maleic anhydride were used as modifiers or compatibilizers. Because of the weak interaction between CaCO 3 and the PS matrix, the composites with 1 and 3 phr CaCO 3 loadings exhibited apparently higher melt shear rates under the same shear stress with respect to the matrix polymer. The storage moduli for the composites increased with low CaCO 3 concentrations. The results showed that CaCO 3 had some effects on the compatibility of PS/SBS (or SBS–MAH)/CaCO 3 composites, in which SBS could effectively retard the movement of PS chain segments. The improvement of compatibility, due to the chemical interaction between CaCO 3 and the grafted maleic anhydride, had obvious effects on the rheological behavior of the composites, the melt shear rate of the composites decreased greatly, and the results showed that nano‐CaCO 3 could plasticize the PS matrix to some extent. Rheological methods provided an indirect but useful characterization of the composite structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006