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Amir Saadat, Hossein Nazockdast, Fatemeh Sepehr, Milad Mehranpoor
Viscoelastic modeling of extrudate swell of Acrylonitrile-Butadiene-Styrene/Clay nanocomposite

Appl. Rheol. 23:1 (2013) 12131 (11 pages)

The aim of the present work was to predict the extrudate swelling behavior of organoclay containing Acrylonitrile- Butadiene-Styrene (ABS) nanocomposite. The modeling was performed on the basis of unconstrained recovery concept originally introduced by Tanner but employing Wagner viscoelastic model with generalized Wagner damping function which is believed to be capable of taking into account the effect of organoclay on viscoelastic properties of nanocomposite sample. This approach enabled us to evaluate the effect of organoclay on extrudate swell in terms of disentanglement kinetics and chain relaxation behavior. In our modeling, the effect of die entrance region on the extent of extrudate swelling was also considered. In order to evaluate the validity of our modeling, the extrudate swell was measured as a function of wall shear stress for samples varying in organoclay content. The results predicted from the model were found to be in relatively good agreement with the experimental results.

Cite this publication as follows:
Saadat A, Nazockdast H, Sepehr F, Mehranpoor M: Viscoelastic modeling of extrudate swell of Acrylonitrile-Butadiene-Styrene/Clay nanocomposite, Appl. Rheol. 23 (2013) 12131.

Ehssan Nazockdast, Hossein Nazockdast
Rheological Modeling of Polymer/layered silicate Nanocomposites

Appl. Rheol. 21:2 (2011) 25434 (11 pages)

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 σMP 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 σMP. 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.

Cite this publication as follows:
Nazockdast E, Nazockdast H: Rheological Modeling of Polymer/layered silicate Nanocomposites, Appl. Rheol. 21 (2011) 25434.

Reza Foudazi, Hossein Nazockdast
Rheology of Polypropylene/Liquid Crystalline Polymer Blends: Effect of Compatibilizer and Silica

Appl. Rheol. 20:1 (2010) 12218 (9 pages)

The effect of classical compatibilizers and silica fillers, which are a new potential type of compatibilizers, on the rheological properties of PP/LCP blends was investigated.The frequency sweep, shear stress growth and stress relaxation upon cessation of steady shear were performed to probe the effect of the interfacial modification and the role of silica, on the rheological behaviour of the blend. It was found that SEBS-g-MA improves the interfacial interaction more than SEBS due to the possible chemical bonding between maleic anhydride groups and LCP chains. The results showed while the hydrophilic silica fills both matrix and the LCP dispersed phases, the hydrophobic silica has some compatibilizing effect on PP/LCP blend samples.

Cite this publication as follows:
Foudazi R, Nazockdast H: Rheology of Polypropylene/Liquid Crystalline Polymer Blends: Effect of Compatibilizer and Silica, Appl. Rheol. 20 (2010) 12218.

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