Rheology of concentrated coagulating suspensions in non-aqueous media

Schreuder, Fwam; Stein, H.N.

doi:10.1007/bf01332683

Cited by 16 publications

(5 citation statements)

References 17 publications

(17 reference statements)

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“…-The slope of the cross section in case of the condition fi = constant can, for dilute suspensions, be calculated with the aid of Eqs. (15) and (20): ?m(P) log ?nAO) +onst I 1 (32) In the case of non-Newtonian liquids, the slope of the J$ = const line can, at the present state of science, not be calculated on theoretical grounds. However, below we will give experimental evidence that, for a wide range of power exponents (0.1 < n < 1.01, the quantity KS is con-stant with value 2.5, implying the initial (at a-0) slope calculated in Eq.…”

Section: Relative Viscosity At Equal Macroscopic Shear Stressesmentioning

confidence: 98%

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The Einstein coefficient of suspensions in generalized Newtonian liquids

Lavèn

Stein²

1991

Journal of Rheology

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SynopsisA new, theoretically more satisfactory, definition for relative viscosities of suspensions in generalized Newtonian media is presented, which according to the viscosities of suspensions and pure liquids should be compared to equal aver--aged squared strain rates 3 in the liquid phases. value of 2.5 over the whole range of n. According to the other definitions, KE is 2.5 only for n = 1; with n decreasing to zero, KE decreases linearly to 0.75 (n, under equal strain rate) or rises exponentially to m (7,. under equal strain stress). The values of KE, as deduced from experiments, obey the theoretical interrelations derived. There are strong indications that the value of n has no influence on the inhomogeneity in rate of strain in dilute suspensions.

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Section: Relative Viscosity At Equal Macroscopic Shear Stressesmentioning

confidence: 98%

“…However, below we will give experimental evidence that, for a wide range of power exponents (0.1 < n < 1.01, the quantity KS is con-stant with value 2.5, implying the initial (at a-0) slope calculated in Eq. (32) to have a value of -10/7, independent of the power-law exponent.…”

Section: Relative Viscosity At Equal Macroscopic Shear Stressesmentioning

confidence: 99%

The Einstein coefficient of suspensions in generalized Newtonian liquids

Lavèn

Stein²

1991

Journal of Rheology

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“…Hydrophilic fumed silica can be chemically modified to hydrophobic fumed silica easily, 3 and has extremely large and smooth non-porous surfaces 2,4,5 promoting the strong physical contact between filler and polymer matrix. In addition, the particle-particle interactions of fumed silicas lead to the agglomerates and particle networks related to the shear thinning effect, 6,7 and H. Barthel ascertained that these interactions depend heavily on the difference of polarity between filler and liquid medium. 8 Thus, if the fumed silicas have similar hydrophobic/hydrophilic properties to polymer matrix, they would be more effectively dispersed and wetted with matrix, and It is expected that fumed silicas act as new suitable nano-reinforcement to improve the heat deflection temperature and the barrier to diffusion of solvent apart from increasing the modulus even at low filler content.…”

Section: Introductionmentioning

confidence: 99%

Poly(ethylene terephthalate)(PET) nanocomposites filled with fumed silicas by melt compounding

Chung

Hahm

et al. 2002

Macromol. Res.

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PET nanocomposites filled with fumed silicas were prepared via direct melt compounding method at various mixing conditions such as filler type and filler content. Some fumed silicas were pre-treated to improve the wettability and dispersibility, and principal characterizations were performed to investigate the effects of nano fumed silicas on polymer matrix. Hydrophobic fumed silica (M-FS), which has the similar contact angles of water with neat PET, acted as the best reinforcement for the thermal stability and mechanical properties of PET nanocomposite, and FE-SEM images also showed that M-FS was uniformly dispersed into matrix and had good wettability. But, some filler (O-FS) had low dispersibility and caused the deterioration of mechanical properties. Besides, the results of DSC revealed the nucleation effect of all fillers in polymer matrix, and PET nanocomposite filled with hydrophilic fumed silica (FS) showed markedly the characteristic dynamic rheological properties such as shear thinning behavior at very low frequencies and the decrease of viscosity.

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“…The giant floc model Stein, 1983, 1984;Schreuder et al, 1986Schreuder et al, , 1987Laven et al, 1988) The giant floc model has been developed for coagulated suspensions of high solid volume fraction (larger than about 0.35) in which separation of discrete flocs is not observed even if densities are not matched. Use of the overall solid volume fraction for characterizing the local environment of a particle then introduces a negligible error.…”

Section: Theorymentioning

confidence: 99%

“…The giant floc model Stein, 1983, 1984;Schreuder and Stein, 1987;Laven et al, 1988) is based on the same idea (see section on Theory). The model starts from the idea that, at low shear rates, the shear is not distributed homogeneously but limited to certain shear planes.…”

Section: Introductionmentioning

confidence: 99%

Visualization of the breakdown of dilute particles gels during steady-shear

Folkersma¹,

Diemen²,

Lavèn³

et al. 1998

Rheologica Acta

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A feature of models concerning the rheology of coagulated suspensions is the development of shear planes. An experimental setup was developed in which we investigated, by visual analysis, whether shear planes really develop in such systems during steady-shear. A transparent coagulated PTFE dispersion was used, in which the refractive indices of the continuous and dispersed phases were matched, for the formation of a gel. Coagulation was effected by adding NaCl to a concentration of 0.5 M. Polystyrene particles were built into the gel structure as tracer particles. During steady-shear the velocities and trajectories of the tracer particles were analyzed by Particle Tracking Velocimetry (PTV). Indeed layers with approximately the same velocity were observed for a coagulated PTFE-gel, during steady-shear. Deviations from rectilinear motion of the tracer particles were observed. These observations correspond with the assumptions of the giant floc model in which the shear is not distributed homogeneously, but limited to certain shear planes. Deviations from rectilinear motion of the tracer particles in a dilute gel correspond with the results found by Folkersma et al. (1998) in which the distance by which a moving particle entrains its neighbours was assumed to be larger at low volume fractions (&0.1) than at high volume fractions (&0.4).

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Rheology of concentrated coagulating suspensions in non-aqueous media

Cited by 16 publications

References 17 publications

The Einstein coefficient of suspensions in generalized Newtonian liquids

The Einstein coefficient of suspensions in generalized Newtonian liquids

Poly(ethylene terephthalate)(PET) nanocomposites filled with fumed silicas by melt compounding

Visualization of the breakdown of dilute particles gels during steady-shear

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