Linear/Nonlinear Rheological Properties and Percolation Threshold of Polydimethylsiloxane Filled with Calcium Carbonate

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The dynamic rheological properties of hydroxyl-terminated polydimethyllsiloxane (PDMS) filled with calcium carbonate (CaCO3) were investigated systematically over a broad temperature range from −40 to 50°C. The results reveal that with an increase of filler volume fraction (φ), the span of the linear viscoelastic region in which dynamic storage modulus (G′) is constant narrows and the relaxation time of the compounds shifts to longer time scales. Beyond the critical φ (φc = 0.069), G′ remarkably increases and exhibits a "pseudo solid-like" behavior in the low frequency (ω) region, meanwhile the width and height of the modulus plateau increase with increasing φ. On the other hand, the "Cole-Cole" plots of G′ against dynamic loss modulus (G″) at different temperatures indicate that the microstructure of compounds with relative high φ is distinct from those of compounds with low φ. The reasons for "pseudo solid-like" behavior are attributed to the agglomeration of filler particles and the formation of percolated filler network structure due to filler-polymer and filler-filler interactions. When φ<φc, the nonhydrodynamic force of polymer matrix is predominant, while particle-particle interactions play an important role when φ>φc.
一般社団法人　日本レオロジー学会の論文
2007-12-15