Journal articles: 'Dynamic shear rheology'

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Nakayama, Yasuya, Kiyoyasu Kataoka, and Toshihisa Kajiwara. "Dynamic Shear Responses of Polymer-polymer Interfaces." Nihon Reoroji Gakkaishi 40, no. 5 (2013): 245–52. http://dx.doi.org/10.1678/rheology.40.245.

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Lade, Rohit, Kailas Wasewar, Rekha Sangtyani, Arvind Kumar, Diwakar Shende, and Dilip Peshwe. "Dynamic shear rheology of nanocomposite propellant suspension." Emerging Materials Research 8, no. 2 (June 2019): 258–64. http://dx.doi.org/10.1680/jemmr.18.00011.

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Kulmyrzaev, Asylbek, and David Julian McClements. "High frequency dynamic shear rheology of honey." Journal of Food Engineering 45, no. 4 (September 2000): 219–24. http://dx.doi.org/10.1016/s0260-8774(00)00062-5.

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Li, Wei Hua, and Xian Zhou Zhang. "Rheology of Magnetorheological Shear Thickening Fluids." Advanced Materials Research 32 (February 2008): 161–64. http://dx.doi.org/10.4028/www.scientific.net/amr.32.161.

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This paper presents fabrication and characterizing of a new functional material, magnetorheological shear thickening fluid (MRSTF), by mixing micron-sized magnetizable particles with nano-sized silica particle based shear thickening fluid. Dynamic properties of the MRSTF were characterized by using a parallel-plate rheometer. The effects of steady-state shear rate and magnetic field on MRSTF rheological properties were addressed. The suspension shows an abrupt increase in complex viscosity beyond a critical dynamic shear rate and a magnetic field controllable characteristic, as well as reversible.

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Triantafillopoulos, Nick, Bruce Schreiner, James Vaughn, and Douglas Bousfield. "Latex Carpet Compound Rheology." Applied Rheology 18, no. 6 (December 1, 2008): 64250–1. http://dx.doi.org/10.1515/arh-2008-0023.

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Abstract This is a study of three-phase foam rheology to qualify penetration in to backing webs during frothed carpet compounds applications. Transient viscosity as a function of shear rate under a short time period is proposed to characterize flow of these compounds in response to a rapidly changing shear field during their application. We developed a fluid dynamic model that predicts the shear and pressure distributions in the compound during its processing in a metering nip based on process parameters and rheological results. We tested frothed compound formulations that are empirically known to be “penetrating” and “non-penetrating” based on the choice of soap (frothing surfactant). Formulated at the same froth density, penetrating to carpet backing compounds had large froth bubbles, relatively low transient shear viscosity and showed increasing foam breakdown due to shear when compared to non-penetrating compounds. Such frothed compounds readily collapse under shear and have relatively low dynamic stability, so the transition from a three-phased (air/aqueous/solid) to a two-phased (water/solid) system occurs much easier and faster during application. The model predicts the shear rate development and a small difference in the pressure distributions in the applicator nip between these formulations, but reduction in drainage for the non-penetrating formulation.

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Prabhu, Tekkati Ajeeth, and Anugrah Singh. "Rheology and microstructure of discontinuous shear thickening suspensions." Journal of Rheology 66, no. 4 (July 2022): 731–47. http://dx.doi.org/10.1122/8.0000317.

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We report experimental studies on rheology and microstructure in discontinuous shear thickening of fumed silica suspensions. Formation of particle clusters was observed after the critical shear rate, and their size increases during shear thickening. At higher shear rates, these clusters were found to break down due to strong shear forces, and a continuous decrease in viscosity was observed. The suspension viscosity and the first normal stress difference variation with the shear rate showed similar dependence. The sign of first normal stress difference was negative during shear thickening, which is consistent with the hydrodynamic model of cluster formation. A linear variation of the first normal stress difference with shear rate during shear thickening further indicates its predominant hydrodynamic origin and supports the recent Stokesian dynamics simulation studies on discontinuous shear thickening based on the hydrodynamic model of nonsmooth colloids by Wang et al. [J. Rheol. 64, 379–394 (2020)]. On the other hand, a nonlinear decrease in the first normal stress difference with shear rate in the second shear-thinning region is primarily due to breaking of large clusters into smaller ones and with a possibility of frictional contacts within these hydroclusters. The oscillatory shear measurements were also performed and the samples displayed strain thickening similar to shear thickening. The similarity between the steady and dynamic shear rheology at high strain amplitudes was observed using the modified Cox–Merz rule.

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BAGCHI, PROSENJIT, and R. MURTHY KALLURI. "Dynamic rheology of a dilute suspension of elastic capsules: effect of capsule tank-treading, swinging and tumbling." Journal of Fluid Mechanics 669 (January 13, 2011): 498–526. http://dx.doi.org/10.1017/s0022112010005161.

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Three-dimensional numerical simulations are used to study the effect of unsteady swinging and tumbling motion on the rheology of a dilute suspension of oblate-shaped elastic capsules. Unlike a suspension of initially spherical capsules undergoing the steady tank-treading motion for which the rheology is constant in time, the suspension of non-spherical capsules is time-dependent due to the unsteady capsule motion. In a simple shear flow, the non-spherical capsules undergo a transition from the tank-treading/swinging to the tumbling motion with a reduction in the shear rate or an increase in the ratio of the internal to external fluid viscosities. We find that the time-averaged rheology obtained for the non-spherical capsules undergoing the unsteady motion is qualitatively similar to that obtained for the spherical capsules undergoing the steady tank-treading motion, and that the tank-treading-to-tumbling transition has only a marginal effect. The time-averaged rheology exhibits a shear viscosity minimum when the capsules are in a swinging motion at high shear rates but not at low shear rates. This is a remarkable departure from the behaviour of a vesicle suspension which exhibits a shear viscosity minimum at the point of transition. We find that the shear viscosity in a capsule suspension can decrease as well as increase with increasing viscosity ratio during both tank-treading and tumbling motions, while that of a vesicle suspension always decreases in tank-treading motion and increases in tumbling motion. We then seek to connect the time-dependent rheology with the time-dependent membrane tension, capsule orientation, deformation and tank-treading velocity. At low shear rates, the numerical results exhibit a similar trend to that predicted by analytical theory for rigid ellipsoids undergoing tumbling motion. The trend differs during swinging motion due to the periodic deformation and time-dependent variation of the membrane stress. The elastic component of the shear stress is minimum when the capsules are maximally compressed, and is maximum when the capsules are maximally elongated. In contrast, the viscous component is related to the periodic variation of the tank-treading velocity synchronized with the swinging motion, and the rate of capsule elongation or compression. The swinging or tumbling velocity makes no contribution to the time-dependent rheology.

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Pyromali, Christina, Yanzhao Li, Flanco Zhuge, Charles-André Fustin, Evelyne van Ruymbeke, and Dimitris Vlassopoulos. "Nonlinear shear rheology of single and double dynamics metal-ligand networks." Journal of Rheology 66, no. 6 (November 1, 2022): 1223–35. http://dx.doi.org/10.1122/8.0000429.

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We present a systematic experimental study of the shear rheology of metallosupramolecular assemblies based on entangled telechelic star polymers comprising one (single dynamic network) or two (double dynamics network) types of physical bonds with the aim to unravel the role of concentration and strength of these bonds on the nonlinear response. Model dynamic networks functionalized with terpyridine ligands were formed by adding different metal ions with increasing bonding strength, zinc, copper, and cobalt. The dynamics are driven by entanglement/disentanglement processes and a ligand exchange mechanism. Steady-state viscosities of single and double dynamics networks collapse onto a universal curve over a wide range of Weissenberg numbers based on terminal time (up to about 300 for single and 1000 for double), exhibiting stronger shear thinning (with an exponent of −0.76) compared to entangled neutral star polymers. Double dynamics networks consisting of two different metal ions (with different lifetimes) exhibit stronger mechanical coherence (rate-dependent fractional viscosity overshoot) and accumulate larger strain at steady-state flow compared to single-ion counterparts. The shear stress growth function signals exhibit weak, albeit unambiguous shear strain hardening, which becomes more pronounced for stronger associations. They also exhibit double overshoot, which reflects the interplay of association strength and chain deformation. Increasing the strength of associations leads to the failure of the Cox–Merz rule, which is more severe for single dynamic networks. The markedly different behavior of double dynamics networks is attributed to the fact that at sufficiently high ion content, the weaker bond acts as a sacrificial component, which provides local energy dissipation and enhances the overall deformability. This bears analogies with their linear viscoelastic response, which has revealed that the arm disentanglement (delayed due to the reversible bonds) effectively interpolates between the two single dynamic network components, depending on composition. Our results suggest ways to tailor the mechanical properties of this class of materials by judicious choice of the type and content of the ion.

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Aime, S., and L. Cipelletti. "Probing shear-induced rearrangements in Fourier space. I. Dynamic light scattering." Soft Matter 15, no. 2 (2019): 200–212. http://dx.doi.org/10.1039/c8sm01563e.

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Aime, S., and L. Cipelletti. "Probing shear-induced rearrangements in Fourier space. II. Differential dynamic microscopy." Soft Matter 15, no. 2 (2019): 213–26. http://dx.doi.org/10.1039/c8sm01564c.

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Llorens, Maria-Gema, Albert Griera, Florian Steinbach, Paul D. Bons, Enrique Gomez-Rivas, Daniela Jansen, Jens Roessiger, Ricardo A. Lebensohn, and Ilka Weikusat. "Dynamic recrystallization during deformation of polycrystalline ice: insights from numerical simulations." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2086 (February 13, 2017): 20150346. http://dx.doi.org/10.1098/rsta.2015.0346.

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The flow of glaciers and polar ice sheets is controlled by the highly anisotropic rheology of ice crystals that have hexagonal symmetry (ice lh). To improve our knowledge of ice sheet dynamics, it is necessary to understand how dynamic recrystallization (DRX) controls ice microstructures and rheology at different boundary conditions that range from pure shear flattening at the top to simple shear near the base of the sheets. We present a series of two-dimensional numerical simulations that couple ice deformation with DRX of various intensities, paying special attention to the effect of boundary conditions. The simulations show how similar orientations of c -axis maxima with respect to the finite deformation direction develop regardless of the amount of DRX and applied boundary conditions. In pure shear this direction is parallel to the maximum compressional stress, while it rotates towards the shear direction in simple shear. This leads to strain hardening and increased activity of non-basal slip systems in pure shear and to strain softening in simple shear. Therefore, it is expected that ice is effectively weaker in the lower parts of the ice sheets than in the upper parts. Strain-rate localization occurs in all simulations, especially in simple shear cases. Recrystallization suppresses localization, which necessitates the activation of hard, non-basal slip systems. This article is part of the themed issue ‘Microdynamics of ice’.

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Frihart, Charles R., and Matthew Gargulak. "Use of Dynamic Shear Rheology to Understand Soy Protein Dispersion Properties." Polymers 14, no. 24 (December 15, 2022): 5490. http://dx.doi.org/10.3390/polym14245490.

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Soy flour dispersions are used as adhesives for bonding interior wood laminates, but the high viscosity of these dispersions requires low solids in the adhesive formulations; the greater water content causes excessive steam pressure during hot press manufacturing. This limits the utility of soy adhesives in replacing urea–formaldehyde adhesives; thus, understanding the cause of high soy viscosities is important. Lack of literature on aqueous soy flour dispersion rheology led to our dynamic rheology studies of these dispersions to understand high viscosity and the effect of various additives. Even at low soy solids, the elastic nature outweighs the viscous properties at low shear, although increasing the shear results in shear-thinning behavior after the yield point. At even higher shear, beyond the flow point where the storage and loss moduli cross, some of the dispersions show an additional shear thinning transition. The comparison of the rheological properties of aqueous dispersions of the soy flour and protein isolate, and another natural protein, ovalbumin from egg whites, led to a better understanding of different types of rheological behaviors. The experimental observations of two observed shear thinning events for soy are consistent with the model of dispersed particles, forming clusters that then form large scale flocculants.

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Williams, Ian, Erdal C. Oğuz, Hartmut Löwen, Wilson C. K. Poon, and C. Patrick Royall. "The rheology of confined colloidal hard disks." Journal of Chemical Physics 156, no. 18 (May 14, 2022): 184902. http://dx.doi.org/10.1063/5.0087444.

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Colloids may be treated as “big atoms” so that they are good models for atomic and molecular systems. Colloidal hard disks are, therefore, good models for 2d materials, and although their phase behavior is well characterized, rheology has received relatively little attention. Here, we exploit a novel, particle-resolved, experimental setup and complementary computer simulations to measure the shear rheology of quasi-hard-disk colloids in extreme confinement. In particular, we confine quasi-2d hard disks in a circular “corral” comprised of 27 particles held in optical traps. Confinement and shear suppress hexagonal ordering that would occur in the bulk and create a layered fluid. We measure the rheology of our system by balancing drag and driving forces on each layer. Given the extreme confinement, it is remarkable that our system exhibits rheological behavior very similar to unconfined 2d and 3d hard particle systems, characterized by a dynamic yield stress and shear-thinning of comparable magnitude. By quantifying particle motion perpendicular to shear, we show that particles become more tightly confined to their layers with no concomitant increase in density upon increasing the shear rate. Shear thinning is, therefore, a consequence of a reduction in dissipation due to weakening in interactions between layers as the shear rate increases. We reproduce our experiments with Brownian dynamics simulations with Hydrodynamic Interactions (HI) included at the level of the Rotne–Prager tensor. That the inclusion of HI is necessary to reproduce our experiments is evidence of their importance in transmission of momentum through the system.

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Lanotte, Luca, Johannes Mauer, Simon Mendez, Dmitry A. Fedosov, Jean-Marc Fromental, Viviana Claveria, Franck Nicoud, Gerhard Gompper, and Manouk Abkarian. "Red cells’ dynamic morphologies govern blood shear thinning under microcirculatory flow conditions." Proceedings of the National Academy of Sciences 113, no. 47 (November 9, 2016): 13289–94. http://dx.doi.org/10.1073/pnas.1608074113.

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Blood viscosity decreases with shear stress, a property essential for an efficient perfusion of the vascular tree. Shear thinning is intimately related to the dynamics and mutual interactions of RBCs, the major component of blood. Because of the lack of knowledge about the behavior of RBCs under physiological conditions, the link between RBC dynamics and blood rheology remains unsettled. We performed experiments and simulations in microcirculatory flow conditions of viscosity, shear rates, and volume fractions, and our study reveals rich RBC dynamics that govern shear thinning. In contrast to the current paradigm, which assumes that RBCs align steadily around the flow direction while their membranes and cytoplasm circulate, we show that RBCs successively tumble, roll, deform into rolling stomatocytes, and, finally, adopt highly deformed polylobed shapes for increasing shear stresses, even for semidilute volume fractions of the microcirculation. Our results suggest that any pathological change in plasma composition, RBC cytosol viscosity, or membrane mechanical properties will affect the onset of these morphological transitions and should play a central role in pathological blood rheology and flow behavior.

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Kim, Bongsu, Soyoung Kwon, Manhee Lee, QHwan Kim, Sangmin An, and Wonho Jhe. "Probing nonlinear rheology layer-by-layer in interfacial hydration water." Proceedings of the National Academy of Sciences 112, no. 51 (December 7, 2015): 15619–23. http://dx.doi.org/10.1073/pnas.1515033112.

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Viscoelastic fluids exhibit rheological nonlinearity at a high shear rate. Although typical nonlinear effects, shear thinning and shear thickening, have been usually understood by variation of intrinsic quantities such as viscosity, one still requires a better understanding of the microscopic origins, currently under debate, especially on the shear-thickening mechanism. We present accurate measurements of shear stress in the bound hydration water layer using noncontact dynamic force microscopy. We find shear thickening occurs above ∼ 106s−1shear rate beyond 0.3-nm layer thickness, which is attributed to the nonviscous, elasticity-associated fluidic instability via fluctuation correlation. Such a nonlinear fluidic transition is observed due to the long relaxation time (∼ 10−6s) of water available in the nanoconfined hydration layer, which indicates the onset of elastic turbulence at nanoscale, elucidating the interplay between relaxation and shear motion, which also indicates the onset of elastic turbulence at nanoscale above a universal shear velocity of ∼ 1 mm/s. This extensive layer-by-layer control paves the way for fundamental studies of nonlinear nanorheology and nanoscale hydrodynamics, as well as provides novel insights on viscoelastic dynamics of interfacial water.

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Aufderhorst-Roberts, Anders, and Gijsje H. Koenderink. "Stiffening and inelastic fluidization in vimentin intermediate filament networks." Soft Matter 15, no. 36 (2019): 7127–36. http://dx.doi.org/10.1039/c9sm00590k.

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Donley, Gavin J., Minaspi Bantawa, and Emanuela Del Gado. "Time-resolved microstructural changes in large amplitude oscillatory shear of model single and double component soft gels." Journal of Rheology 66, no. 6 (November 2022): 1287–304. http://dx.doi.org/10.1122/8.0000486.

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Soft particulate gels can reversibly yield when sufficient deformation is applied, and the characteristics of this transition can be enhanced or limited by designing hybrid hydrogel composites. While the microscopic dynamics and macroscopic rheology of these systems have been studied separately in detail, the development of direct connections between the two has been difficult, particularly with regard to the nonlinear rheology. To bridge this gap, we perform a series of large amplitude oscillatory shear (LAOS) numerical measurements on model soft particulate gels at different volume fractions using coarse-grained molecular dynamics simulations. We first study a particulate network with local bending stiffness and then we combine it with a second component that can provide additional cross-linking to obtain two-component networks. Through the sequence of physical processes (SPP) framework, we define time-resolved dynamic moduli, and by tracking the changes in these moduli through the period, we can distinguish transitions in the material behavior as a function of time. This approach helps us establish the microscopic origin of the nonlinear rheology by connecting the changes in dynamic moduli to the corresponding microstructural changes during the deformation including the nonaffine displacement of particles, and the breakage, formation, and orientation of bonds.

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Zhang, Jiu Peng, Li Xu, and Jian Zhong Pei. "Viscoelastic Analysis of Asphalt Mastic Based on Micromechanics." Advanced Materials Research 266 (June 2011): 38–41. http://dx.doi.org/10.4028/www.scientific.net/amr.266.38.

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In this study, the stiffening effect of fillers on asphalt binders was characterized through micromechanics and rheology methods. The dynamic shear rheometer (DSR) was used to measure viscoelastic properties of asphalt mastic. Mechanical volume filling effects and additional interacting mechanisms within mastic systems are discussed on the basis of micromechanics-rheology model to predict the complex shear modulus of asphalt mastic from the measured mastic data. It is observed that the phase angle ranges from 88.8o to 89.0o, does not significantly change due to limestone fillers addition. The analytical model prediction of complex shear modulus based on the dynamic shear modulus can be used. Using the nonlinear regression, the Einstein coefficient KE is 4.22, 5.09 and 7.44 for asphalt mixed with limestone, cement and hydrated lime, respectively. Beside, the SEM results explain why the mastic system with hydrated lime shows the highest KE. The behavior of hydrated lime fillers filled mastics is probably due to physico–chemical interaction, which can be validated by further research.

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Yoo, Byoungseung. "Steady and dynamic shear rheology of glutinous rice flour dispersions." International Journal of Food Science and Technology 41, no. 6 (June 2006): 601–8. http://dx.doi.org/10.1111/j.1365-2621.2005.01074.x.

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Le Moigne, Nicolas, Martien van den Oever, and Tatiana Budtova. "Dynamic and capillary shear rheology of natural fiber-reinforced composites." Polymer Engineering & Science 53, no. 12 (March 5, 2013): 2582–93. http://dx.doi.org/10.1002/pen.23521.

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Cho, MyoungLae, Won-Seok Choi, and SangGuan You. "Steady and Dynamic Shear Rheology of Fucoidan-Buckwheat Starch Mixtures." Starch - Stärke 61, no. 5 (May 2009): 282–90. http://dx.doi.org/10.1002/star.200800083.

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Yoo, Dongryel, Chion Kim, and Byoungseung Yoo. "Steady and Dynamic Shear Rheology of Rice Starch-Galactomannan Mixtures." Starch - Stärke 57, no. 7 (July 2005): 310–18. http://dx.doi.org/10.1002/star.200400390.

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Zhang, Jiu Peng, Jian Zhong Pei, and Bing Gang Wang. "Micromechanical-Rheology Model for Predicting the Complex Shear Modulus of Asphalt Mastic." Advanced Materials Research 168-170 (December 2010): 523–27. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.523.

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The dynamic shear rheometer (DSR) was used to measure viscoelastic properties of asphalt mastic. Mechanical volume filling effects and additional interacting mechanisms within mastic systems are discussed on the basis of micromechanical-rheology model to predict the complex shear modulus of asphalt mastic from the measured mastic data. The Einstein coefficient is 3.761, and the maximum volumetric packing fraction is 0.562 for the measured asphalt mastic. The predicted G* of asphalt mastics is very close to the actual value, and the relative error is not exceeding 10%. The micromechanical-rheology model can predict the complex shear modulus of the asphalt mastic from the viscoelastic property of neat asphalt, the volumetric filler effect and an interactive effect between the filler and the asphalt.

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Hayashi, Chieko, and Tadashi Inoue. "An Apparatus for Dynamic Birefringence Measurement under Oscillatory Shear Flow Using an Oblique Laser Beam." Nihon Reoroji Gakkaishi 37, no. 4 (2009): 205–10. http://dx.doi.org/10.1678/rheology.37.205.

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Zhu, Yun, Michael McNeary, Neal Breslin, and Jing Liu. "Effect of Structures on Rheology in a Model Magnetorheological Fluid." International Journal of Modern Physics B 13, no. 14n16 (June 30, 1999): 2044–51. http://dx.doi.org/10.1142/s0217979299002125.

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The structure dependence of rheology on a model magnetorheological fluid is investigated experimentally. We find that the column-dominated structure formed under slow ramping of the magnetic field has higher dynamic yield stress than the "bent-wall" dominated structure formed under the fast ramping field. The measurement of the shear rate loop under fast ramping shows an abnormal rheological hysteresis. It indicates a shear assisted structural transition from the "bent-wall" dominated structure to a more stable structure. A possible shear-induced structure with circular stripes is suggested.

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Lee, Hyang Mok, Jin Woo Lee, and O. Ok Park. "Rheology and Dynamics of Water-in-Oil Emulsions under Steady and Dynamic Shear Flow." Journal of Colloid and Interface Science 185, no. 2 (January 1997): 297–305. http://dx.doi.org/10.1006/jcis.1996.4592.

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McKay, K. W., W. G. Miller, J. E. Puig, and E. I. Franses. "STEADY AND DYNAMIC SHEAR RHEOLOGY OF DISPERSIONS OF LYOTROPIC LIQUID CRYSTALS." Journal of Dispersion Science and Technology 12, no. 1 (January 1991): 37–58. http://dx.doi.org/10.1080/01932699108913104.

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Mukhopadhyay, Anal K., and Sehoon Jang. "Predicting Cement–Admixture Incompatibilities with Cement Paste Rheology." Transportation Research Record: Journal of the Transportation Research Board 2290, no. 1 (January 2012): 19–29. http://dx.doi.org/10.3141/2290-03.

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The complex interaction between cement and the chemical and mineral admixtures in concrete mixture sometimes causes unpredictable concrete performance in the field, generally defined as concrete incompatibilities. Cement paste rheology measurements—rather than traditional workability tests—can effectively detect these incompatibilities in concrete before the concrete is placed to avoid setting-time, workability, and curing-related issues, which sometimes lead to early-age cracking, especially in severe weather conditions. The objective of the present study is to examine the applicability of the Superpave® dynamic shear rheometer to measure cement paste rheology and to identify incompatibilities between cement and the admixtures based on cement paste rheological behavior. Extensive laboratory investigation showed that dynamic shear rheometer in modified form could measure cement paste rheology with permissible repeatability and sensitivity and has great potential in identifying the incompatibilities between cement and the admixtures. Heat of hydration data from an isothermal calorimeter test and the setting time results of the mixtures studied have strongly supported the rheology results. A procedure to formulate the rheology-based acceptance criteria has been developed on the basis of the available test results. Further refinement of these acceptance criteria based on detailed work covering a wide range of incompatibilities and validation through a round-robin testing program is warranted. This research will ultimately help concrete producers and district laboratories detect problematic combinations of concrete ingredients during the mixture design process.

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Salmo, Iselin C., Ken S. Sorbie, and Arne Skauge. "The Impact of Rheology on Viscous Oil Displacement by Polymers Analyzed by Pore-Scale Network Modelling." Polymers 13, no. 8 (April 13, 2021): 1259. http://dx.doi.org/10.3390/polym13081259.

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Several experimental studies have shown significant improvement in heavy oil recovery with polymers displaying different types of rheology, and the effect of rheology has been shown to be important. These experimental studies have been designed to investigate why this is so by applying a constant flow rate and the same polymer effective viscosity at this injection rate. The types of rheology studied vary from Newtonian and shear thinning behavior to complex rheology involving shear thinning and thickening behavior. The core flood experiments show a significantly higher oil recovery with polyacrylamide (HPAM), which exhibits shear thinning/thickening behavior compared to biopolymers like Xanthan, which is purely shear thinning. Various reasons for these observed oil recovery results have been conjectured, but, to date, a clear explanation has not been conclusively established. In this paper, we have investigated the theoretical rationale for these results by using a dynamic pore scale network model (DPNM), which can model imbibition processes (water injection) in porous media and also polymer injection. In the DPNM, the polymer rheology can be shear thinning, shear thinning/thickening, or Newtonian (constant viscosity). Thus, the local effective viscosity in a pore within the DPNM depends on the local shear rate in that pore. The predicted results using this DPNM show that the polymer causes changes in the local flow velocity field, which, as might be expected, are different for different rheological models, and the changes in the velocity profile led to local diversion of flow. This, in turn, led to different oil recovery levels in imbibition. However, the critical result is that the DPNM modelling shows exactly the same trend as was observed in the experiments, viz. that the shear thinning/thickening polymer gave the highest oil recovery, followed by the Newtonian Case and the purely shear thinning polymer gave the lowest recover, but this latter case was still above the waterflood result. The DPNM simulations showed that the shear-thinning/thickening polymer show a stabilized frontal velocity and increased oil mobilization, as observed in the experiments. Simulations for the shear-thinning polymer show that, in high-rate bonds, the average viscosity is greatly reduced, and this causes enhanced water fingering compared to the Newtonian polymer case. No other a priori model of the two-phase fluid physics of imbibition, coupled with the polymer rheology, has achieved this degree of predictive explanation, of these experimental observations, to our knowledge.

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Uppuluri, Srinivas, Faith A. Morrison, and Petar R. Dvornic. "Rheology of Dendrimers. 2. Bulk Polyamidoamine Dendrimers under Steady Shear, Creep, and Dynamic Oscillatory Shear." Macromolecules 33, no. 7 (April 2000): 2551–60. http://dx.doi.org/10.1021/ma990634u.

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Liu, Zhonghua, Wei Wang, Florian J. Stadler, and Zhi-Chao Yan. "Rheology of Concentrated Polymer/Ionic Liquid Solutions: An Anomalous Plasticizing Effect and a Universality in Nonlinear Shear Rheology." Polymers 11, no. 5 (May 14, 2019): 877. http://dx.doi.org/10.3390/polym11050877.

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An anomalous plasticizing effect was observed in polymer/ionic liquid (IL) solutions by applying broad range of rheological techniques. Poly(ethylene oxide)(PEO)/IL solutions exhibit stronger dynamic temperature dependence than pure PEO, which is in conflict with the knowledge that lower-Tg solvent increases the fractional free volume. For poly(methy methacrylate)(PMMA)/IL solutions, the subtle anomaly was detected from the fact that the effective glass transition temperature Tg,eff of PMMA in IL is higher than the prediction of the self-concentration model, while in conventional polymer solutions, Tg,eff follows the original Fox equation. Observations in both solutions reveal retarded segmental dynamics, consistent with a recent simulation result (Macromolecules, 2018, 51, 5336) that polymer chains wrap the IL cations by hydrogen bonding interactions and the segmental unwrapping delays their relaxation. Start-up shear and nonlinear stress relaxation tests of polymer/IL solutions follow a universal nonlinear rheological behavior as polymer melts and solutions, indicating that the segment-cation interaction is not strong enough to influence the nonlinear chain orientation and stretch. The present work may arouse the further theoretical, experimental, and simulation interests in interpreting the effect of complex polymer-IL interaction on the dynamics of polymer/IL solutions.

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ORPE, ASHISH V., and D. V. KHAKHAR. "Rheology of surface granular flows." Journal of Fluid Mechanics 571 (January 4, 2007): 1–32. http://dx.doi.org/10.1017/s002211200600320x.

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Surface granular flow, comprising granular material flowing on the surface of a heap of the same material, occurs in several industrial and natural systems. The rheology of such a flow was investigated by means of measurements of velocity and number-density profiles in a quasi-two-dimensional rotating cylinder, half-filled with a model granular material – monosize spherical stainless-steel particles. The measurements were made at the centre of the cylinder, where the flow is fully developed, using streakline photography and image analysis. The stress profile was computed from the number-density profile using a force balance which takes into account wall friction. Mean-velocity and root-mean-square (r.m.s.)-velocity profiles are reported for different particle sizes and cylinder rotation speeds. The profiles for the mean velocity superimpose when distance is scaled by the particle diameterdand velocity by a characteristic shear rate$\dot{\gamma}_C = [g\sin(\beta_m-\beta_s)/d\cos\beta_s]^{1/2}$and the particle diameter, where βmis the maximum dynamic angle of repose and βsis the static angle of repose. The maximum dynamic angle of repose is found to vary with the local flow rate. The scaling is also found to work for the r.m.s. velocity profiles. The mean velocity is found to decay exponentially with depth in the bed, with decay length λ = 1.1d. The r.m.s. velocity shows similar behaviour but with λ = 1.7d. The r.m.s. velocity profile shows two regimes: near the free surface the r.m.s. velocity is nearly constant and below a transition point it decays linearly with depth. The shear rate, obtained by numerical differentiation of the velocity profile, is not constant anywhere in the layer and has a maximum which occurs at the same depth as the transition in the r.m.s. velocity profile. Above the transition point the velocity distributions are Gaussian and below the transition point the velocity distributions gradually approach a Poisson distribution. The shear stress increases roughly linearly with depth. The variation in the apparent viscosity η with r.m.s. velocityushows a relatively sharp transition at the shear-rate maximum, and in the region below this point the apparent viscosity η ∼u−1.5. The measurements indicate that the flow comprises two layers: an upper low-viscosity layer with a nearly constant r.m.s. velocity and a lower layer of increasing viscosity with a decreasing r.m.s. velocity. The thickness of the upper layer depends on the local flow rate and is independent of particle diameter while the reverse is found to hold for the lower-layer thickness. The experimental data is compared with the predictions of three models for granular flow.

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Run, Ming Tao, Feng Liu, Chun Yan Jiang, and Na Li. "Dynamic Rheology and Thermal Stability of PTT/POE-g-MAH Blends." Advanced Materials Research 382 (November 2011): 260–63. http://dx.doi.org/10.4028/www.scientific.net/amr.382.260.

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The blends of poly (trimethylene terephthalate)(PTT) and maleinized poly (octene-ethylene) copolymer (POE-MAH) were prepared by melt-blending method and their rheology and thermal stability were investigated by using rotational rheometer and thermalgravimetric analyzer (TGA) respectively. The rheological properties of PTT/POE-MAH blends demonstrate that all of the blends belong to the pseudoplastic fluid for their complex viscosity declines with the increasing shear rate. In addition, POE component can strengthen the melt viscosity, so the blend can be processed in the more wider temperature range. Moreover, the complex viscosity become more sensitive to the change of the shear rate, i.e., it decreases more apparently with the increase of the POE-MAH component. The melt flexibility increases apparently with the increase of the POE-g-MAH component. POE-MAH component only has a little depression on the thermal stability of the blends.

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CHAKER, MUSTAPHA, NEAL BRESLIN, and JING LIU. "INFLUENCE ON RHEOLOGY OF STATIC AND DYNAMIC STRUCTURES IN MODEL MAGNETORHEOLOGICAL FLUIDS." International Journal of Modern Physics B 15, no. 06n07 (March 20, 2001): 886–93. http://dx.doi.org/10.1142/s0217979201005404.

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This paper investigates the influence of static and dynamic structures on Rheology in a model magnetorheological fluid. Dynamic structures generated under shear are studied using first a rotational rheometer then an optical image processing system. A microscope allowed us to visualize the different patterns thus generated and compare these results to the measurements obtained with the rheometer. It also enabled us to analyze the various initial static structures formed by an externally applied magnetic field. Besides the well known column-dominated and bent-wall dominated static structures we were able to observe novel, concentric, ring like formations under shear. A dynamic yield stress analysis was conducted for each type of structure along with a statistical approach to further characterize and differentiate the various types of magnetic particle arrangements.

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Lee, Johnny Ching-Wei, Lionel Porcar, and Simon A. Rogers. "Unveiling Temporal Nonlinear Structure–Rheology Relationships under Dynamic Shearing." Polymers 11, no. 7 (July 16, 2019): 1189. http://dx.doi.org/10.3390/polym11071189.

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Understanding how microscopic rearrangements manifest in macroscopic flow responses is one of the central goals of nonlinear rheological studies. Using the sequence-of-physical-processes framework, we present a natural 3D structure–rheology space that temporally correlates the structural and nonlinear viscoelastic parameters. Exploiting the rheo-small-angle neutron scattering (rheo-SANS) techniques, we demonstrate the use of the framework with a model system of polymer-like micelles (PLMs), where we unveil a sequence of microscopic events that micelles experience under dynamic shearing across a range of frequencies. The least-aligned state of the PLMs is observed to migrate from the total strain extreme toward zero strain with increasing frequency. Our proposed 3D space is generic, and can be equally applied to other soft materials under any sort of deformation, such as startup shear or uniaxial extension. This work therefore provides a natural approach for researchers to study complex out-of-equilibrium structure–rheology relationships of soft materials.

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Choi, Hae M., and Byoungseung Yoo. "Steady and dynamic shear rheology of sweet potato starch–xanthan gum mixtures." Food Chemistry 116, no. 3 (October 2009): 638–43. http://dx.doi.org/10.1016/j.foodchem.2009.02.076.

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Singh, Mansi, Sanjeev K. Verma, Ipsita Biswas, and Rajeev Mehta. "Rheology of Fumed Silica and Polyethylene Glycol Shear Thickening Suspension with Nanoclay as an Additive." Defence Science Journal 69, no. 4 (July 15, 2019): 402–8. http://dx.doi.org/10.14429/dsj.69.12420.

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Shear thickening properties of fumed silica-polyethylene glycol (PEG) with shear thickening fluid (STF) of different concentrations and with an organically modified clay, Nanomer I.28 E as nano-additive have been investigated by both steady-state and dynamic state rheology. Difference in rheology if instead of nanoclay, an equal wt% of additional fumed silica is added to 20 per cent fumed silica-PEG200 STF, has been studied. At 25 °C, in case of addition of nanoclay the increase in critical viscosity is less than that observed for same additional amount of fumed silica. Interestingly, an opposite result is seen at higher temperatures i.e. 45 °C and 55 °C. Moreover, the difference in steady-state and dynamic state viscosity values decreases on addition of nanoclay. It is noted that an increase in concentration of clay increases the value of dynamic parameters whereas for STF of only fumed silica particles the values are constant irrespective of the change in concentration. More importantly, ease of processing, elasticity, stability and consistency of rheological results of STF increases to a significant extent on addition of relatively inexpensive nano-additive.

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Stanciu, Ioana. "New relationship to describe the rheology of sunflower oil." Analele Universitatii "Ovidius" Constanta - Seria Chimie 25, no. 1 (June 1, 2014): 28–31. http://dx.doi.org/10.2478/auoc-2014-0005.

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Abstract This paper proposes two new relations of dependence of log dynamic viscosity depending on log absolute temperature shear rates between 3.3 and 120s-1. The constants A, B, and C were determined by Origin 6.0 software by fitting linear or polynomial curves obtained from experimental data. The two proposed relationships give correlation coefficients close to one.

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Ip, Bill, W. D. Hibler, and Greg Flato. "The Effect Of Rheology On Seasonal Sea-Ice Simulations." Annals of Glaciology 14 (1990): 340. http://dx.doi.org/10.3189/s0260305500009046.

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On the seasonal time scales relevant to numerical investigations of climate, the rheology used in large-scale sea ice models significantly affects the ice thickness build-up and ice velocity fields. Plastic rheologies with a normal flow rule have been used to-date in seasonal dynamic thermodynamic simulations. These rheologies have proved useful in simulating discontinuous slip near the coast while still supplying relatively robust velocity fields in the central Arctic Basin. However, as indicated by limited numerical sensitivity studies with different types of elliptical yield curves, the amount of shear strength significantly affects the ice build-up and can possibly cause a stoppage of the ice outflow through Fram Strait. In addition to the shear strength issue, there is also the possibility that non-normal flow rule rheologies, such as the Mohr Coulomb failure criterion used in soil mechanics, may cause somewhat different types of flow patterns, especially in the Fram Strait region. However, to date no seasonal simulations with such non-normal flow rule rheologies have been carried out.In order to investigate the role of different rheologies on the large-scale flow patterns in the Arctic Basin, a more general numerical scheme than that of Hibler (1979) is developed, which allows the simulation of the dynamic thermodynamic behavior of sea ice with a wide variety of different non linear rheologies. Using this numerical scheme, comparative simulations are carried out to seasonal equilibrium with several variations of the Mohr Coulomb rheology and compared to the more standard Elliptical yield curve results. In particular, the main control Mohr Coulomb case is a capped rheology in which the shear strength is taken to be proportional to the compressive stress. In this capped case only shear flow is allowed until a maximum allowable compressive stress is reached. This cap strength is parameterized to be a function of the ice thickness and compactness. For comparison, a simulation with a very large cap strength is also carried out, and an experiment with a similar compressive cap but much lower shear strength. Overall the results are analyzed to determine the sensitivity of the ice build-up to flow rule and shear strength magnitude. In addition special attention is given to the character of the flow and stoppage (if any) through Fram Strait.

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Ip, Bill, W. D. Hibler, and Greg Flato. "The Effect Of Rheology On Seasonal Sea-Ice Simulations." Annals of Glaciology 14 (1990): 340. http://dx.doi.org/10.1017/s0260305500009046.

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On the seasonal time scales relevant to numerical investigations of climate, the rheology used in large-scale sea ice models significantly affects the ice thickness build-up and ice velocity fields. Plastic rheologies with a normal flow rule have been used to-date in seasonal dynamic thermodynamic simulations. These rheologies have proved useful in simulating discontinuous slip near the coast while still supplying relatively robust velocity fields in the central Arctic Basin. However, as indicated by limited numerical sensitivity studies with different types of elliptical yield curves, the amount of shear strength significantly affects the ice build-up and can possibly cause a stoppage of the ice outflow through Fram Strait. In addition to the shear strength issue, there is also the possibility that non-normal flow rule rheologies, such as the Mohr Coulomb failure criterion used in soil mechanics, may cause somewhat different types of flow patterns, especially in the Fram Strait region. However, to date no seasonal simulations with such non-normal flow rule rheologies have been carried out. In order to investigate the role of different rheologies on the large-scale flow patterns in the Arctic Basin, a more general numerical scheme than that of Hibler (1979) is developed, which allows the simulation of the dynamic thermodynamic behavior of sea ice with a wide variety of different non linear rheologies. Using this numerical scheme, comparative simulations are carried out to seasonal equilibrium with several variations of the Mohr Coulomb rheology and compared to the more standard Elliptical yield curve results. In particular, the main control Mohr Coulomb case is a capped rheology in which the shear strength is taken to be proportional to the compressive stress. In this capped case only shear flow is allowed until a maximum allowable compressive stress is reached. This cap strength is parameterized to be a function of the ice thickness and compactness. For comparison, a simulation with a very large cap strength is also carried out, and an experiment with a similar compressive cap but much lower shear strength. Overall the results are analyzed to determine the sensitivity of the ice build-up to flow rule and shear strength magnitude. In addition special attention is given to the character of the flow and stoppage (if any) through Fram Strait.

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41

Run, Ming Tao, Zi Yu Qi, Meng Yao, Wen Zhou, and Bing Tao Xing. "Phase Morphology and Rheology Behaviors of PTT/POE/OMMT Nanocomposites." Solid State Phenomena 181-182 (November 2011): 55–58. http://dx.doi.org/10.4028/www.scientific.net/ssp.181-182.55.

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The phase morphology and dynamic rheology of poly (trimethylene terephthalate)/maleinized poly (octene-ethylene)/organo-montmorillonite nanocomposites were investigated by using transmission electron microscopy (TEM) and rotational rheometer. The results suggest that some of the OMMT are peeled off and the nanosheets are dispersed evenly in the polymer matrix. When the OMMT content is more than 4%, they are tended to form the aggregates in nanocomposites. The nanocomposites’ melt are pseudo-plastic fluid, and both complex viscosity and shear storage modulus increase with increasing OMMT content due to the interaction between the OMMT and polymers. The nanocomposites’ melt show more elasticity behavior with more OMMT content especially at low shear frequencies.

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Lee, Kok Peng Marcian, Milan Brandt, Robert Shanks, and Fugen Daver. "Rheology and 3D Printability of Percolated Graphene–Polyamide-6 Composites." Polymers 12, no. 9 (September 3, 2020): 2014. http://dx.doi.org/10.3390/polym12092014.

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Graphene–polyamide-6 (PA6) composites with up to 17.0%·w/w graphene content were prepared via melt mixing. Oscillatory rheometry revealed that the dynamic viscoelastic properties of PA6 decreased with the addition of 0.1%·w/w graphene but increased when the graphene content was increased to 6.0%·w/w and higher. Further analysis indicated that the rheological percolation threshold was between 6.0 and 10.0%·w/w graphene. The Carreau–Yasuda model was used to describe the complex viscosity of the materials. Capillary rheometry was applied to assess the steady shear rheology of neat PA6 and the 17.0%·w/w graphene–PA6 composite. High material viscosity at low shear rates coupled with intense shear-thinning in the composite highlighted the importance of selecting the appropriate rheological characterisation methods, shear rates and rheological models when assessing the 3D printability of percolated graphene–polymer composites for material extrusion (ME). A method to predict the printability of an ME filament feedstock, based on fundamental equations describing material flow through the printer nozzle, in the form of a printing envelope, was developed and verified experimentally. It was found that designing filaments with steady shear viscosities of approximately 15% of the maximum printable viscosity for the desired printing conditions will be advantageous for easy ME processing.

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43

Indei, Tsutomu, and Tetsuharu Narita. "Microrheological study of single chain dynamics in semidilute entangled flexible polymer solutions: Crossover from Rouse to Zimm modes." Journal of Rheology 66, no. 6 (November 2022): 1165–79. http://dx.doi.org/10.1122/8.0000402.

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The dynamics of polymer chains in entangled semidilute solution have been of theoretical and experimental interest. Among a number of characteristic lengths and times of the polymer in solution, those of the correlation blob are the key to understand the applicability of the Rouse and Zimm models to rheology of the semidilute solution. Direct rheological measurements of Rouse and Zimm modes are limited as the corresponding time scale is out of the range of classical rheological techniques. We investigated the single chain dynamics of entangled poly(ethylene oxide) in semidilute aqueous solutions by high-frequency micro-rheology based on diffusing-wave spectroscopy compared to classical shear macro-rheology. Concentration dependence of the three characteristic times of the entangled polymer chains, reptation time, entanglement time, and correlation time, was studied with the help of the time-concentration superposition. At the low frequency range, dynamic moduli measured by macro-rheology and micro-rheology showed a good agreement without adjustable parameters. At the higher frequency range, we found the Rouse regime in the mean square displacement of the probe particles and in the magnitude of the complex specific viscosity of the solution. We propose a simple method to estimate the boundary of the Rouse regime. Finally, at the high frequency range, we demonstrate that the contribution of the solvent to the solution viscosity needs to be subtracted to observe the power-law behavior of the Zimm mode.

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44

Wang, Hujun, Yuan Meng, Zhenkun Li, Jiahao Dong, and Hongchao Cui. "Steady-State and Dynamic Rheological Properties of a Mineral Oil-Based Ferrofluid." Magnetochemistry 8, no. 9 (September 13, 2022): 100. http://dx.doi.org/10.3390/magnetochemistry8090100.

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In this study, nanoparticles were suspended in L-AN32 total loss system oil. The thixotropic yield behavior and viscoelastic behavior of ferrofluid were analyzed by steady-state and dynamic methods and explained according to the microscopic mechanism of magneto-rheology. The Herschel–Bulkley (H–B) model was used to fit the ferrofluid flow curves, and the observed static yield stress was greater than the dynamic yield stress. Both the static and dynamic yield stress values increased as the magnetic field increased, and the corresponding shear thinning viscosity curve increased more significantly as the magnetic field strength increased. The amplitude scanning results show that the linear viscoelastic region (LVE) is reached when the shear stress is 10%. The frequency scanning results showed that the storage modulus increased with the increase of the frequency at first. The storage modulus increased steadily at a higher frequency range, while the loss modulus increased slowly at the initial stage and rapidly at the later stage. In the amplitude sweep and frequency sweep experiments, the energy storage modulus and loss modulus are enhanced with the decrease of temperature. These findings are helpful to better understand the microscopic mechanism of magneto-rheology of ferrofluids, and also provide guidance for many practical applications.

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45

Arif, Mohammad, Saurabh Kango, and Dinesh Kumar Shukla. "Effect of slip boundary condition and non-newtonian rheology of lubricants on the dynamic characteristics of finite hydrodynamic journal bearing." Surface Topography: Metrology and Properties 10, no. 1 (January 11, 2022): 015002. http://dx.doi.org/10.1088/2051-672x/ac4403.

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Abstract In the present study, the influence of various slip zone locations on the dynamic stability of finite hydrodynamic journal bearing lubricated with non-Newtonian and Newtonian lubricants has been investigated. Linearized equation of motion with free vibration of rigid rotor has been used to find the optimum location of the slip region with maximum stability margin limit. It has been observed that bearing with interface of slip and no-slip region near the upstream side of minimum film-thickness location is effective in improving the direct and cross stiffness coefficient, critical mass parameter, and critical whirling speed. The magnitude of dynamic performance parameters with slip effect is highly dependent on the rheology of lubricant. Shear-thinning lubricants combined with slip boundary condition shows higher dynamic stability as compared to the Newtonian lubricants under the conventional boundary condition. For all considered rheology of lubricants, the dynamic stability of bearing with slip effect is improving by increasing the eccentricity ratio.

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46

Mohammadi, Farough, and Ramin Sedaghati. "Dynamic mechanical properties of an electrorheological fluid under large-amplitude oscillatory shear strain." Journal of Intelligent Material Systems and Structures 23, no. 10 (May 6, 2012): 1093–105. http://dx.doi.org/10.1177/1045389x12442013.

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In the present study, the shear stress response and the dynamic mechanical properties of an electrorheological fluid are experimentally investigated for small/large shear strain amplitude at moderate range of frequencies and different field intensities. A new efficient constitutive model has also been proposed, which can accurately predict the measured experimental data. Compared with the Fourier transformation rheology, the proposed model requires less number of parameters in order to predict the stress response and the mechanical properties, including storage and loss moduli for different strain amplitudes, frequencies, and field intensities. This leads to simplify the parameter identification in order to predict the material response using the optimization methods.

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Khanna, Y. P. "Dynamic melt rheology. I: Re-examining dynamic viscosity in relationship to the steady shear flow viscosity." Polymer Engineering and Science 31, no. 6 (March 1991): 440–44. http://dx.doi.org/10.1002/pen.760310610.

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48

Shih, Wei-Heng, and Leh-Lii Pwu. "Rheology of aqueous boehmite-coated silicon nitride suspensions and gels." Journal of Materials Research 10, no. 11 (November 1995): 2808–16. http://dx.doi.org/10.1557/jmr.1995.2808.

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The rheological properties of boehmite-coated silicon nitride aqueous suspensions and gels are reported. In unidirectional rheological tests, it was found that the boehmite coating reduces the viscosity of the suspensions over a wide range of shear rates and volume fractions of particles. The suspension shear stress as a function of shear rate can be described by the Bingham model, and the Bingham yield stresses of boehmite-coated silicon nitride suspensions are lower than those of the uncoated suspensions. The reduction in the viscosity and the Bingham yield stress is attributed to a shallower secondary minimum in the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential between coated particles than that for uncoated silicon nitride particles. Moreover, at low values of pH, the coated silicon nitride suspensions gelled over time, and the viscoelastic behavior of the gels was studied by dynamic oscillatory tests. It was found that the shear modulus (G′) and loss modulus (G″) remain constant up to a certain strain amplitude, γ°, beyond which G′ and G″ begin to vary. The value of G′ in the linear region increases exponentially, whereas γ° decreases exponentially with the volume fraction of coated silicon nitride particles. The exponential behavior of the shear modulus G′ of the gels is similar to the exponential pressure-density relationship found in the previous pressure filtration study, indicating that particulate rearrangement occurs as volume fraction of particles is increased.

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Bourg, Violette, Rudy Valette, Nicolas Le Moigne, Patrick Ienny, Valérie Guillard, and Anne Bergeret. "Shear and Extensional Rheology of Linear and Branched Polybutylene Succinate Blends." Polymers 13, no. 4 (February 22, 2021): 652. http://dx.doi.org/10.3390/polym13040652.

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The molecular architecture and rheological behavior of linear and branched polybutylene succinate blends have been investigated using size-exclusion chromatography, small-amplitude oscillatory shear and extensional rheometry, in view of their processing using cast and blown extrusion. Dynamic viscoelastic properties indicate that a higher branched polybutylene succinate amount in the blend increases the relaxation time due to an increased long-chain branching degree. Branched polybutylene succinate exhibits pronounced strain hardening under uniaxial elongation, which is known to improve processability. Under extensional flow, the 50/50 wt % blend exhibits the same behavior as linear polybutylene succinate.

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KABLA, ALEXANDRE, JULIEN SCHEIBERT, and GEORGES DEBREGEAS. "Quasi-static rheology of foams. Part 2. Continuous shear flow." Journal of Fluid Mechanics 587 (August 31, 2007): 45–72. http://dx.doi.org/10.1017/s0022112007007276.

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The evolution of a bidimensional foam submitted to continuous quasi-static shearing isinvestigated both experimentally and numerically. We extract, from the images of the sheared foam, the plastic flow profiles as well as the local statistical properties of the stress field. When the imposed strain becomes larger than the yield strain, the plastic events develop large spatial and temporal correlations, and the plastic flow becomes confined to a narrow shear band. This transition and the steady-state regime of flow are investigated by first focusing on the elastic deformation produced by an elementary plastic event. This allows us to understand (i) the appearance of long-lived spatial heterogeneities of the stress field, which we believe are at the origin of the shear-banding transition, and (ii) the statistics of the dynamic fluctuations of the stress field induced by plastic rearrangements in the steady-state regime. Movies are available with the online versionof the paper.

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Journal articles on the topic 'Dynamic shear rheology'

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