Rheological behavior and network dynamics of silica filled vinyl-terminated polydimethylsiloxane suspensions

Abstract

Present article reports the rheological properties and network dynamics of fumed silica filled vinyl-terminated polydimethylsiloxane suspensions. The results reveal that as filler loading increases, the span of the linear viscoelastic region with constant dynamic storage modulus is narrowed with increase in strain amplitude while the relaxation time of the compounds get shifted to longer time scales. The dynamics of filler-network indicated significant Payne effect due to fumed silica incorporation into the PDMS matrix. Further, strain-induced agglomeration of fumed silica particles, characterized by a peak in the dynamic loss modulus curve could also be observed. High loss-tangent was observed for lower contents of filler in the suspension, an effect with an apparent relationship to the loosely formed filler-network. The formation of a saturated network structure of fumed silica particles was evident from the dynamic modulus and complex viscosity data, that remained unaffected with frequency till a critical amount of fumed silica loading. Han plots (storage modulus versus loss modulus) revealed the microstructural changes for various filled systems that was attributed to build-up of the filler-network causing an apparent evolution of yielding phenomenon. Van Gurp-Palmen plots (complex modulus versus phase lag) showed that flow behavior of the filled PDMS suspensions resembled to that of typical viscous fluids. POLYM. ENG. SCI., 57:973–981, 2017. © 2016 Society of Plastics Engineers