## Appl Rheol online available publications for selected issue

Follow the blue link(s) below for abstracts and full text pdfs .

► Cite this publication as follows:

Baldi F, Ferri D, Lapasin R, Semenzato A: XIII Italian Conference on Rheology 2014, Appl. Rheol. 24 (2014) 49.

► Cite this publication as follows:

Dhir V: International Conference on Heat Transfer and Fluid Flow (HTTF 2014), Appl. Rheol. 24 (2014) 48.

Measurements and modeling of rheological properties of a high viscosity silicone oil (polydimethylsiloxane, PDMS) at high frequency are reported. The linear viscoelastic properties are measured by small amplitude oscillation shear (SAOS) tests with a rotational rheometer. Furthermore, Diffusing Wave Spectroscopy (DWS) is used, which expands the angular frequency range of the measured loss and storage moduli up to 10^{5}rad/s, in a temperature range of 20 - 70 C. Good agreement between both methods is found in the overlapping frequency region, especially at higher temperatures. The DWS data show that the elastic modulus stays dominant and increases with frequency, without a second cross-over point up till 10^{8}rad/s. Flow curves, measured with rotational and with capillary rheometry up to a shear rate of 7.6 × 10^{4}s^{-1}, show shear thinning behavior, which implies nonlinear viscoelasticity. Comparison of the dynamic and complex viscosity shows that the Cox-Merz rule is valid in a frequency range spanning six orders of magnitude. A multi-element White-Metzner model is proposed as a constitutive equation, which accurately describes the nonlinear viscoelastic properties, including the decrease of the loss and storage moduli during amplitude sweeps in oscillatory shear measurements.► Cite this publication as follows:

Kokuti Z, vanGruijthuijsen K, Jenei M, Toth-Molnar G, Czirjak A, Kokavecz J, Ailer P, Palkovics L, Volker AC, Szabo G: High-frequency rheology of a high viscosity silicone oil using diffusing wave spectroscopy, Appl. Rheol. 24 (2014) 63984.

The knowledge of enzymatic activity is necessary in many industrial processes. The common measurement techniques are time-consuming and therefore cost-intensive. Measurements of viscosities are a promising approach as a fast and cheap testing method. The major challenges are to find a suitable substrate with Newtonian flow behavior throughout the whole testing range as well as a correlation between viscosity of the solution and the decomposed mass. Water based gelatinebuffer- system as substrate is tested extensively regarding the dependence on different solvents, pH-values and gelatine batches. All viscosity measurements are performed with a rotational viscometer. It is shown that the gelatine-buffer-system is independent of the given parameters and found to fulfill the said requirements. A correlation model based on the Martin equation and necessary assumptions are presented. The required parameters intrinsic viscosity and Martin parameter can be derived by few measurements with little effort. The digesting enzyme Trypsin is used as model enzyme in the degradation experiments. The enzyme concentration is varied and the decrease of the viscosity is measured. A dependency between the enzyme concentration and the enzymatic activity or respectively the viscosity decrease is observed.► Cite this publication as follows:

Sellerberg M, DiBartolo D, Oberrecht J, Tiller J, Walzel P: Viscometric measurement of protease activities on gelatine substrate, Appl. Rheol. 24 (2014) 62660.

Fruit juices concentrated by osmotic distillation are characterized by higher organoleptic and sensorial properties than those of juices concentrated by thermal evaporation as confirmed by several research studies. On the other hand, no literature is readily available about the rheological characterization of juices concentrated by osmotic distillation. This work aimed at investigate the rheological behavior of the concentrated blood orange juice prepared from the clarified juice by using thermal evaporation and osmotic distillation processes as a function of solids concentration in the range 115 - 614 g/kg of total soluble solids (TSS) within a range of 20 - 70 C. The effect of the temperature and concentration on the juice viscosity was studied. Arrhenius-type correlation equations for viscosity were used to represent the temperature dependence of viscosity. Values of the Arrhenius equation parameters (flow activation energy) were calculated for the measured viscosities of juices as a function of concentration. Results indicated no significant differences in the rheological behavior for orange juices concentrated with both methods. The juices exhibited a Newtonian behavior regardless of the concentration method.► Cite this publication as follows:

OlivieroRossi C, Destani F, Cassano A: Rheological behavior of blood orange juice concentrated by osmotic distillation and thermal evaporation, Appl. Rheol. 24 (2014) 63776.

The rheological properties of diamond (< 10 nm) in silicone oil (PDMS) were analyzed using steady shear and oscillatory shear measurements. Unlike micron sized diamond suspensions these suspensions were non Newtonian and showed strong viscoelastic behavior without the electric field applied. Furthermore these nanodiamond mixtures showed sigmoidal behavior for their apparent viscosity as the shear rate is increased without the electric field applied. When the electric field was applied the apparent viscosity of the mixtures increased by an order of magnitude at lower shear rates. The effects of electric field and concentration on diamond rheology are both examined. The rate of shear thinning for the mixtures is high when the applied electric field is high. At high shear rates for the mixture the electric field does not have much effect. The flow curve was described by the Herschel-Bulkley model. Yield stress values obtained from the model gives an important relationship between yield stress, electric field and concentration, that is τ ∝Eand where 0.8 <^{n}n< 1.3.► Cite this publication as follows:

McIntyre C, Pereira A: Electrorheology of nanodiamond/PDMS nanofluids in steady and oscillatory shear, Appl. Rheol. 24 (2014) 63471.

We modify a commercial rheometer so that the disks are aligned perpendicular to the axis of rotation with a precision in parallelism of about 1 μm independent of the rheometer reading. This leads to decrease the zero-gap error by a factor of 25 and more. It enables samples to be studied at gap widths well below the absolute error of commercial rheometers. At gap widths of 20 μm, the modification allows the measurement range to be extended to shear rates up to 10^{5}s^{-1}enabling to measure low viscosities such as that of solvents or water and of dilute polymer solutions. The measurements are restricted mainly by the torque resolution at low shear rates and by inertia at high shear rates.► Cite this publication as follows:

Dakhil H, Wierschem A: Measuring low viscosities and high shear rates with a rotational rheometer in a thin-gap parallel-disk configuration, Appl. Rheol. 24 (2014) 63795.

© Applied Rheology 2024