Rheology, defined as the science of deformation and flow of matter, is a multidisciplinary scientific field, covering both fundamental and applied approaches. The study of rheology includes both ...experimental and computational methods, which are not mutually exclusive. Its practical importance embraces many processes, from daily life, like preparing mayonnaise or spread an ointment or shampooing, to industrial processes like polymer processing and oil extraction, among several others. Practical applications include also formulations and product development.
This Special Issue aims to present the latest advances in the fields of experimental and computational rheology applied to the most diverse classes of materials (foods, cosmetics, pharmaceuticals, polymers and biopolymers, multiphasic systems and composites) and processes.
This Special Issue will comprise, not only original research papers, but also review articles.
Aim: The aim of the study was to work out the composition of cream with extract of sapropel from Prybych deposits, Volyn region, Ukraine, and to determine its organoleptic, physicochemical indices, ...structural and mechanical (rheological) parameters, colloidal and thermal stability, as well as to justify the choice of effective preservatives. Materials and Methods: The following materials were employed: Extract of sapropel from Prybych deposits; emulsion base, containing corn oil, emulsifier №1, cetylstearyl alcohol, and purified water. To carry out the research a set of methods (centrifugal, thermal, and potentiomentric), to analyze colloidal and thermal stability, and to determine pH values of the tested samples were used. Rheological properties of the samples were determined on the rotating viscometer. Results: There was determined the influence of the extract on physicochemical and rheological properties of the emulsion base; all the experimental samples remain thermally and colloidally stable and have satisfactory organoleptic properties; incorporation of SE into an emulsion base in a concentration of up to 20% retains structural and mechanical properties of the base. Conclusion: As the results of the carried out experimental investigations, the effect of the SE on physicochemical and rheological properties of its emulsion base. Microbiological research showed that the maximum reduction of the number of viable cells of microorganisms was observed applying as preservatives euxyl K 100 (0.1%) and nisin (0.01%).
Comb and bottlebrush polymers present a wide range of rheological and mechanical properties that can be controlled through their molecular characteristics, such as the backbone and side chain lengths ...as well as the number of branches per molecule or the grafting density. This review investigates the impact of these characteristics specifically on the zero shear viscosity, strain hardening behavior, and plateau shear modulus. It is shown that for a comb polymer with an entangled backbone and entangled side chains, a maximum in the strain hardening factor and minimum in the zero shear viscosity η0 can be achieved through selection of an optimum number of branches q. Bottlebrush polymers with flexible filaments and extremely low plateau shear moduli relative to linear polymers open the door for a new class of solvent‐free supersoft elastomers, where their network modulus can be controlled through both the degree of polymerization between crosslinks, nx, and the length of the side chains, nsc, with GBB0≈ρkTnx−1(nsc+1)−1.
Comb and bottlebrush polymers exhibit unusual rheological properties compared to their linear analogs due to side‐chain crowding. Investigation of the melt rheology of model branched polymers with controlled grafting density, side chain, and backbone lengths allows correlation of macroscopic flow properties such as zero shear viscosity, plateau modulus, and strain‐hardening behavior to conformational regimes by means of scaling analysis and tube theory.
Cranberry waste contains potentially valuable components, such as proanthocyanidins, flavanols, and xyloglucan. Highly-purified xyloglucan (XG) from cranberries were studied through steady and ...oscillatory shear rheology at various concentrations and temperatures. At room temperature, an apparent yield stress is observed and the storage modulus exceeds the loss modulus (G′>G′′) for concentrations of 0.5 wt% and higher, indicating that the XG solution has formed a physical hydrogel. Thermoresponsive gelation is observed with a five-order of magnitude increase in shear moduli as it undergoes a weak to strong gel transition around 52 °C. The gelation time was 5 min with an observed storage moduli up to 3500 Pa. Cranberry-based XG exhibits thermoresponsive behavior at concentrations as low as 0.1 wt% (w/v), which is significantly lower than prior gelation studies of XG from other sources. The formation of a weak gel at room temperature and large storage moduli observed at room temperature is likely associated with the low level of impurities and small amount of galactose present in the XG chains.
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Saponins are natural surfactants which can provide highly viscoelastic interfaces. This property can be used to quantify precisely the effect of interfacial dilatational elasticity on ...the various rheological properties of bulk emulsions.
We measured the interfacial dilatational elasticity of adsorption layers from four saponins (Quillaja, Escin, Berry, Tea) adsorbed on hexadecane-water and sunflower oil-water interfaces. In parallel, the rheological properties under steady and oscillatory shear deformations were measured for bulk emulsions, stabilized by the same saponins (oil volume fraction between 75 and 85%).
Quillaja saponin and Berry saponin formed solid adsorption layers (shells) on the SFO-water interface. As a consequence, the respective emulsions contained non-spherical drops. For the other systems, the interfacial elasticities varied between 2 mN/m and 500 mN/m. We found that this interfacial elasticity has very significant impact on the emulsion shear elasticity, moderate effect on the dynamic yield stress, and no effect on the viscous stress of the respective steadily sheared emulsions. The last conclusion is not trivial, because the dilatational surface viscoelasticity is known to have strong impact on the viscous stress of steadily sheared foams. Mechanistic explanations of all observed effects are described.
We review the dynamics of particle laden interfaces, both particle monolayers and particle+surfactant monolayers. We also discuss the use of the Brownian motion of microparticles trapped at fluid ...interfaces for measuring the shear rheology of surfactant and polymer monolayers. We describe the basic concepts of interfacial rheology and the different experimental methods for measuring both dilational and shear surface complex moduli over a broad range of frequencies, with emphasis in the micro-rheology methods. In the case of particles trapped at interfaces the calculation of the diffusion coefficient from the Brownian trajectories of the particles is calculated as a function of particle surface concentration. We describe in detail the calculation in the case of subdiffusive particle dynamics. A comprehensive review of dilational and shear rheology of particle monolayers and particle+surfactant monolayers is presented. Finally the advantages and current open problems of the use of the Brownian motion of microparticles for calculating the shear complex modulus of monolayers are described in detail.
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•We have reviewed the background of surface rheology techniques.•The dynamics of particles trapped at interfaces has been described.•Brownian trajectories lead to the diffusion coefficient for interacting particles.•Particles strongly modify the dilational and shear rheology of particle laden monolayers.•Particles can be used as probes for measuring the shear rheology of monolayers.
Fluid–fluid interfaces stabilized by proteins, protein aggregates, polymers, or colloidal particles, tend to have a complex microstructure. Their response to an applied deformation is often highly ...nonlinear, even at small deformation (rates). The nonlinearity of the response is a result of changes in the interfacial microstructure. Most of the studies on interfacial rheology of complex interfaces currently available in the scientific literature, focus on the linear response regime. Since multiphase systems such as emulsions or foam are routinely exposed to large and fast deformations, characterization of the nonlinear response of complex interfaces is highly relevant. In this paper we review the recent work on nonlinear rheology of complex interfaces, both in shear and dilatational deformations. We also discuss several methods currently available for analyzing nonlinear interfacial rheology data, and recent progress in modeling nonlinear interfacial rheology, using nonequilibrium thermodynamic frameworks.
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•The response of complex interfaces to large deformations is often nonlinear.•This paper reviews the recent work on nonlinear responses in shear and dilatation.•In dilatational rheology strain amplitude variations are often not applied.•Lissajous curves and stress decomposition with special functions are useful tools.•Constitutive modeling of surface rheology is a field still in its infancy.
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The surface dilatational and shear moduli of surfactant and protein interfacial layers can be derived from surface pressures measured with a Wilhelmy plate parallel, ΔΠpar and ...perpendicular ΔΠperp to the barriers in a Langmuir trough.
Applying area oscillations, A0+ ΔAeiωt, in a rectangular Langmuir trough induces changes in surface pressure, ΔΠpar and ΔΠperp for monolayers of soluble palmitoyl-lysophosphatidylcholine (LysoPC), insoluble dipalmitoylphosphatidylcholine (DPPC), and the protein β-lactoglobulin to evaluate Es∗+Gs∗=A0ΔΠparΔA and Es∗-Gs∗=A0ΔΠperpΔA. Gs∗ was independently measured with a double-wall ring apparatus (DWR) and Es∗ by area oscillations of hemispherical bubbles in a capillary pressure microtensiometer (CPM) and the results were compared to the trough measurements.
For LysoPC and DPPC, A0ΔΠparΔA≅A0ΔΠperpΔA meaning Es∗≫Gs∗ and Es∗≅A0ΔΠparΔA≅A0ΔΠperpΔA. Trough values for Es∗ were quantitatively similar to CPM when corrected for interfacial curvature. DWR showed G∗ was 4 orders of magnitude smaller than Es∗ for both LysoPC and DPPC. For β-lactoglobulin films, A0ΔΠparΔA>A0ΔΠperpΔA and Es∗ and Gs∗ were in qualitative agreement with independent CPM and DWR measurements. For β-lactoglobulin, both Es∗ and Gs∗ varied with film age and history on the trough, suggesting the evolution of the protein structure.
•Deposition\aggregation\precipitation of asphaltene generates substantial flow assurance issues with considerable financial ramifications.•This review work drew on more than 150 sources, including ...papers on interfacial rheology, bulk rheology, rheological modelling, and simulations.•Waxy and polymeric matrices, oil-water emulsions, and other media are among the media in which asphaltene can become embedded.
Asphaltene is a component of crude oil that has been linked to serious production and transportation issues. It is a solid oil component with various shapes and molecular compositions. Deposition\aggregation\precipitation of asphaltene generates substantial flow assurance issues with considerable financial ramifications. Furthermore, emulsion formation is also found to be a serious challenge in the petroleum business. The increased viscosity of the crude oil is due to emulsified water droplets in the system. We will look at the difficulty that the petroleum sector is facing with asphaltene via a rheology lens. In this review study, we provide a brief introduction to asphaltene for the interested reader, followed by a review of the literature on asphaltene flow behavior in diverse mediums including waxy matrix, polymer matrix, oil\water emulsions, and so on. More than 150 references were used to compile this review paper including papers that explore interfacial rheology, bulk rheology, rheological modeling, and simulations.
Rheological assessment and characterization of fresh cement pastes play a key role in designing mixes for a variety of applications, including 3D printing. However, there is conflicting information ...regarding certain rheological concepts in the literature. In this paper, the most recent advances in measurement and characterization methods of dynamic rheology, static rheology, shear thickening or shear thinning, viscoelasticity, and thixotropic structural build-up via the use of rheometers as measurement tools are systematically discussed. The links and differences between these methodologies are examined from the perspective of applied rheology, highlighting the significance of adopting appropriate testing methods for cement pastes with diverse rheological characteristics. The information and discussion presented in this study will also enable researchers and practitioners working in the field of rheology to distinguish some key concepts that relate to different substances with diverse rheological properties. These include properties that are critical for cement pastes, such as thixotropy and structural build-up, establishing the groundwork for different users to make more informed choices regarding the identification of reasonable test methods suitable for projects with various demands.
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