Studies on the steady and dynamic rheological properties of poly(dimethyl‐siloxane) filled with calcium carbonate based on superposition of its relative functions

The steady and dynamic rheological properties of hydroxyl‐terminated polydimethylsiloxane filled with calcium carbonate were investigated by varying the filler volume fraction (Φ) from 0 to 18.2 vol %. The results reveal that there exists a “percolation threshold” (Φ c = 3.6%) for the suspensions, below which both the “Cox‐Merz” and modified “Cox‐Merz” rule are competent over the whole shear regions. However, these two rules breakdown and a characteristic plateau appears in low frequency regions for suspensions with Φ > Φ c . The reasons for this can be ascribed to the contributions of nonhydrodynamic forces and formation of percolated filler network structure with increasing Φ. Moreover, using a concentration‐dependent parameter, B (Φ), superposition curves of dynamic complex modulus (| G *|) and shear stress (τ) for all suspensions were obtained through shifting | G *| curves along the ordinate and τ functions along the abscissa using different B (Φ) as shifting factor. Unfortunately, the reasonable superposition range is restricted in the high ω or $\dot \gamma$ regions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008