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.
Rheology is primarily concerned with materials: scientific, engineering and everyday products whose mechanical behaviour cannot be described using classical theories. From biological to geological ...systems, the key to understanding the viscous and elastic behaviour firmly rests in the relationship between the interactions between atoms and molecules and how this controls the structure, and ultimately the physical and mechanical properties. Rheology for Chemists An Introduction takes the reader through the range of rheological ideas without the use of the complex mathematics. The book gives particular emphasis on the temporal behaviour and microstructural aspects of materials, and is detailed in scope of reference. An excellent introduction to the newer scientific areas of soft matter and complex fluid research, the second edition also refers to system dimension and the maturing of the instrumentation market. This book is a valuable resource for practitioners working in the field, and offers a comprehensive introduction for graduate and post graduates. "... well-suited for self-study by research workers and technologists, who, confronted with technical problems in this area, would like a straightforward introduction to the subject of rheology." Chemical Educator, "... full of valuable insights and up-to-date information." Chemistry World
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.
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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.
SUMMARY
Tectonic plate motions predominantly result from a balance between the potential energy change of the subducting slab and viscous dissipation in the mantle, bending lithosphere and slab–upper ...plate interface. A wide range of observations from active subduction zones and exhumed rocks suggest that subduction interface shear zone rheology is sensitive to the composition of subducting crustal material—for example, sediments versus mafic igneous oceanic crust. Here we use 2-D numerical models of dynamically consistent subduction to systematically investigate how subduction interface viscosity influences large-scale subduction kinematics and dynamics. Our model consists of an oceanic slab subducting beneath an overriding continental plate. The slab includes an oceanic crustal/weak layer that controls the rheology of the interface. We implement a range of slab and interface strengths and explore how the kinematics respond for an initial upper mantle slab stage, and subsequent quasi-steady-state ponding near a viscosity jump at the 660-km-discontinuity. If material properties are suitably averaged, our results confirm the effect of interface strength on plate motions as based on simplified viscous dissipation analysis: a ∼2 order of magnitude increase in interface viscosity can decrease convergence speeds by ∼1 order of magnitude. However, the full dynamic solutions show a range of interesting behaviour including an interplay between interface strength and overriding plate topography and an end-member weak interface-weak slab case that results in slab break-off/tearing. Additionally, for models with a spatially limited, weak sediment strip embedded in regular interface material, as might be expected for the subduction of different types of oceanic materials through Earth’s history, the transient response of enhanced rollback and subduction velocity is different for strong and weak slabs. Our work substantiates earlier suggestions as to the importance of the plate interface, and expands the range of quantifiable links between plate reorganizations, the nature of the incoming and overriding plate and the potential geological record.
Rheological behaviour is an important fluid property that severely impacts its flow behaviour and many aspects related to this. In the case of activated sludge, the apparent viscosity has an ...influence on e.g. pumping, hydrodynamics, mass transfer rates, sludge–water separation (settling and filtration). It therefore is an important property related to process performance, including process economics. To account for this, rheological behaviour is being included in process design, necessitating its measurement. However, measurements and corresponding protocols in literature are quite diverse, leading to varying results and conclusions. In this paper, a vast amount of papers are critically reviewed with respect to this and important flaws are highlighted with respect to rheometer choice, rheometer settings and measurement protocol. The obtained rheograms from experimental efforts have frequently been used to build viscosity models. However, this is not that straightforward and a lot of errors can be detected with respect to good modelling practice, including fair model selection criteria, qualitative parameter estimations and proper model validation. These important steps are however recurrently violated, severely affecting the model reliability and predictive power. This is illustrated with several examples. In conclusion, dedicated research is required to improve the rheological measurements and the models derived from them. At this moment, there is no guidance with respect to proper rheological measurements. Moreover, the rheological models are not very trustworthy and remain very “black box”. More insight in the physical background needs to be gained. A model-based approach with dedicated experimental data collection is the key to address this.
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► Rheological behaviour of activated sludge is an important fluid property. ► Reported literature on AS rheological measurements and modelling is inconclusive. ► Protocols for proper rheological measurements are absent in literature. ► Good modelling practice is often violated when modelling AS rheological behaviour. ► More profound knowledge on AS rheology is needed.
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