Ehssan Nazockdast, Hossein Nazockdast
Rheological Modeling of Polymer/layered silicate Nanocomposites
Appl. Rheol. 21:2 (2011) 25434 (11 pages)Abstract: This work takes a phenomenological approach to modeling the rheology of polymer/clay nanocomposites in (shear rate) γ ≤ 1 / s based on experimental observations [10]. The total stress was divided to three contributions: Matrix stress, σM, inter-particle (matrix/particle) stress, σP, and hydrodynamic stress σH. Based on the superposition of complex viscosities, η*, plotted against strain rate amplitude, γ0ω, at different nonlinear strain amplitudes, a modified Bingham-type constitutive equation proposed by Doiraswamy et. al [16] was used to model σM+σP while σH was modeled by using constitutive equation proposed by Lipscomb et. al [25] for ellipsoidal particles. The comparison between experimental and modeling results showed that steady hydrodynamic stress in simple shear flows scales with complex viscosities in oscillatory experiments when compared at γ = γ0ω. On the basis of this observation, the network-like behavior of the polymer nanocomposite was attributed to retarded chain dynamics as a result of polymer/clay interactions. In order to take into account the thixotropic behavior of network structure, the constitutive equation proposed by Coussot [18] was employed for modeling σM+σP. Both Coussot and Doraiswamy equations gave a reasonable quantitative prediction of transient stress in simple shear flow up to shear rates as high as γ = 0.1 / s. © 2011 Applied Rheology.
DOI 10.3933/ApplRheol-21-25434
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