Viscoelastic properties of suspensions with weakly interacting particles

Bayram, Göknur; Yilmazer, Ülkü; Orbey, Neşe

doi:10.1002/(sici)1097-4628(19981017)70:3<507::aid-app12>3.0.co;2-y

Cited by 7 publications

(6 citation statements)

References 19 publications

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“…A higher relaxation time indicates that the mean lifetime of the junction zones of xanthan is higher than that of zones formed by guar entanglements. In general, we observed that the G i values decreased with an increase in relaxation time (Table 4) for the same conditions of temperature and gum concentration, which is in agreement with the values obtained by Bayram et al (1998). The increase in relaxation time could be associated with the formation of intermolecular aggregates, which was facilitated by an increase in the polysaccharide concentration and the biopolymer characteristics.…”

Section: Dynamic Rheologysupporting

confidence: 89%

Dynamic and steady: shear rheological properties of xanthan and guar gums dispersed in yellow passion fruit pulp (Passiflora edulis f. flavicarpa)

Moraes

Fasolin

Cunha

et al. 2011

Braz. J. Chem. Eng.

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-Yellow passion fruit pulp is unstable, presenting phase separation that can be avoided by the addition of hydrocolloids. For this purpose, xanthan and guar gum [0.3, 0.7 and 1.0% (w/w)] were added to yellow passion fruit pulp and the changes in the dynamic and steady-shear rheological behavior evaluated. Xanthan dispersions showed a more pronounced pseudoplasticity and the presence of yield stress, which was not observed in the guar gum dispersions. Cross model fitting to flow curves showed that the xanthan suspensions also had higher zero shear viscosity than the guar suspensions, and, for both gums, an increase in temperature led to lower values for this parameter. The gums showed different behavior as a function of temperature in the range of 5-35 o C. The activation energy of the apparent viscosity was dependent on the shear rate and gum concentration for guar, whereas for xanthan these values only varied with the concentration. The mechanical spectra were well described by the generalized Maxwell model and the xanthan dispersions showed a more elastic character than the guar dispersions, with higher values for the relaxation time. Xanthan was characterized as a weak gel, while guar presented a concentrated solution behavior. The simultaneous evaluation of temperature and concentration showed a stronger influence of the polysaccharide concentration on the apparent viscosity and the G' and G" moduli than the variation in temperature.

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Section: Dynamic Rheologysupporting

confidence: 89%

Dynamic and steady: shear rheological properties of xanthan and guar gums dispersed in yellow passion fruit pulp (Passiflora edulis f. flavicarpa)

Moraes

Fasolin

Cunha

et al. 2011

Braz. J. Chem. Eng.

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“…(2) and (3) are both ineffective for such materials. Bayram et al (1998) showed the validity of the Cox-Merz rule for Newtonian suspensions up to a particle volume fraction of 30%, while Kaully et al (2007) showed its validity up to a particle volume fraction of 20-40%, depending on the particle size distribution. Both papers showed that for higher concentrations, the complex viscosity resulted smaller than the dynamic ones ( * < ), in contrast to the case of shear thinning suspensions.…”

Section: Introductionmentioning

confidence: 95%

The microstructural change causing the failure of the Cox-Merz rule in Newtonian suspensions: experiments and simulations

et al. 2021

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Newtonian non-Brownian concentrated suspensions show a mismatch between the steady state and the complex viscosity, whatever the strain amplitude imposed in the oscillatory flow. This result is counterintuitive in the two extreme cases of vanishing strain amplitude and very large one. In the first case, the oscillatory flow should not be able to alter the steady microstructure, as well as in the other opposite limit for which the strain amplitude is so high that the oscillatory flow resembles a steady flow reversal. If the microstructure is not altered with respect to the steady one, similarly the complex viscosity should be equal to the steady one. We here investigate experimentally and numerically the origin of the viscosities mismatch at any imposed strain amplitude. We focus on the first two or three cycles of oscillations and different particle concentrations. Experimental and numerical results agree and allow to prove that for intermediate amplitudes, the oscillatory shear induces the breakage of particle clusters and the microstructure modifies so to minimise particle collisions. For very small strain amplitudes, the oscillatory shear only induces the rotation of few couples of touching particles and the complex viscosity results slightly smaller than the steady one, while for very large strains, the oscillatory flow reshuffles the particles inducing a microstructure as clustered as the steady state one but with a different angular distribution function. We show that the vast majority of the microstructure rearrangement takes place in the first half cycle of oscillation.

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“…In this study, the linear least squares method (19, 23,24) was used in order to obtain the relaxation time and the relaxation strength.…”

Section: Analysis Of Viscoelastic Propertiesmentioning

confidence: 99%

“…Another useful method of analysis is the calculation of the relaxation times distribution using oscillatory shear data (19)(20)(21)(22)(23)(24). The calculated relaxation strength-relaxation time distribution can then be used to determine parameters such as the zero shear rate viscosity, rubbery plateau and mean relaxation time providing information about the molecular structure of the blend.…”

Section: Introductionmentioning

confidence: 99%

Viscoelastic properties of reactive and non‐reactive blends of ethylene‐methyl acrylate copolymers with styrene‐maleic anhydride copolymer

Bayram

Yilmazer

Xanthos

2001

Polymer Engineering & Sci

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The effects of compatibilizing reactions on the viscoelastic properties and morphology of ethylene-methyl acrylate copolymers were studied. Potentially reactive blends of styrene-maleic anhydride copolymer (SMAH) and a terpolymer of ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA) were compared with a nonreactive blend of SMAH and an ethylene/methyl acrylate (E-MA) copolymer with similar rheological properties. Melt mixing was carried out in a batch mixer and in a co-rotating twin screw extruder. The morphology of the reactive blends showed smaller domain sizes than the non-reactive blends, and the viscoelastic properties of the blends were very different. The storage and loss moduli and the complex viscosity of the reactive blends were greater than those of non-reactive blends. The reactive blends had a higher zero shear viscosity, plateau modulus and mean relaxation time than their non-reactive counterparts, indicating a higher degree of melt elasticity. The melt elasticity was maximum at 25% functionalized ethylene-methyl acrylate concentration.

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Viscoelastic properties of suspensions with weakly interacting particles

Cited by 7 publications

References 19 publications

Dynamic and steady: shear rheological properties of xanthan and guar gums dispersed in yellow passion fruit pulp (Passiflora edulis f. flavicarpa)

Dynamic and steady: shear rheological properties of xanthan and guar gums dispersed in yellow passion fruit pulp (Passiflora edulis f. flavicarpa)

The microstructural change causing the failure of the Cox-Merz rule in Newtonian suspensions: experiments and simulations

Viscoelastic properties of reactive and non‐reactive blends of ethylene‐methyl acrylate copolymers with styrene‐maleic anhydride copolymer

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