Viscosity Eta Research Articles

The shear viscosity of parton matter under anisotropic scatterings

The shear viscosity eta of a quark–gluon plasma in equilibrium can be calculated analytically using multiple methods or numerically using the Green–Kubo relation. It has been realized, which we confirm here, that the Chapman–Enskog method agrees well with the Green–Kubo result for both isotropic and anisotropic two-body scatterings. We then apply the Chapman–Enskog method to study the shear viscosity of the parton matter from a multi-phase transport model. In particular, we study the parton matter in the center cell of central and midcentral Au + Au collisions at 200A GeV and Pb + Pb collisions at 2760A GeV, which is assumed to be a plasma in thermal equilibrium but partial chemical equilibrium. As a result of using a constant Debye mass or cross section sigma for parton scatterings, the eta /s ratio increases with time (as the effective temperature decreases), contrary to the trend preferred by Bayesian analysis of the experimental data or pQCD results that use temperature-dependent Debye masses. At sigma =3 mb that enables the transport model to approximately reproduce the elliptic flow data of the bulk matter, the average eta /s of the parton matter in partial equilibrium is found to be very small, between one to two times 1/(4pi ).

Coalescence of two growing bubbles in a Hele\u2013Shaw cell

An understanding of the dynamics of growth-driven coalescence is important in diverse fields across natural science and engineering. Motivated by the bubble coalescence in magma during volcanic eruptions, we study both experimentally and theoretically the coalescence of two growing bubbles in a Hele–Shaw cell. In our system, bubbles grow by gas expansion due to decompression and the diffusional influx of dissolved gas in the liquid. Our experiments show that the evolution of film thickness and bubble shape depends on viscosity, decompression rate, and cell gap. Through a scaling analysis and a perturbation approximation, we find that the hydrodynamic interaction between two bubbles is characterized by a film capillary number Ca_f=(eta {dot{R}}/sigma )(R/D)^2 depending on viscosity eta, bubble radius R, growth rate {dot{R}}, interfacial tension sigma, and cell gap D. The experimental results demonstrate that the film capillary number solely determines the bubble distortion just before coalescence. Under our experimental conditions, bubble coalescence occurs below a critical value of a nominal film capillary number defined as a film capillary number evaluated when two undeformed circular bubbles come into contact.

Heat capacity, entropy, configurational entropy, and viscosity of magnesium silicate glasses and liquids

In this work, five Mg-silicate glasses with compositions between MgSiO_3 and Mg_2SiO_4 were synthesized by aerodynamic levitation combined with laser melting. Low-temperature heat capacity (C_p) was measured (by relaxation calorimetry in the range 2–310 K) for all of them, with the resulting vibrational entropies at T = 298.15 K: sample MG50 with composition Mg_{0.996}SiO_{2.996} and entropy 72.88 J mol^{-1} K^{-1}; MG54 Mg_{1.174}SiO_{3.174} 78.54; MG58 Mg_{1.364}SiO_{3.364} 85.05; MG62 Mg_{1.611}SiO_{3.611} 91.40; and MG67 Mg_{1.907}SiO_{3.907} 102.75. Heat capacity of the glasses is higher than that of the corresponding crystal mixtures below 200 K but plunges below the C_{p,mathrm{crystal}} at higher temperatures. High-temperature C_p was measured (by differential scanning calorimetry in the range 300–970 K) for MG50 and MG67 up to approx 1000 K. Using our C_p data, selected data for entropies of fusion, C_p of crystals, and fictive temperatures, the configurational entropy (S_mathrm{conf}) at glass transition temperature (T_mathrm{g}) were calculated. For the near-forsterite glass MG67, the S_mathrm{conf} is 1.9 J mol^{-1} K^{-1} at T_mathrm{g} = 1040 K. As this small value is a difference of several large numbers, its uncertainty is relatively high; we consider a conservative estimate of 15 J mol^{-1} K^{-1}. Using the expression log eta = A + B/[T S_mathrm{conf}(T)], the available experimental viscosities (eta ) and the temperature-dependent configurational entropy from our work, we refined the parameters A = -2.34 and B = 76,500 for this equation, with S_mathrm{conf} (T) = 1.90+(83.7 ln (T/1040)). The configurational entropy for the enstatitic MG50 glass is 16.8 J mol^{-1} K^{-1} at T_mathrm{g} = 1063 K. The presented data can be combined with enthalpies of formation and thermophysical properties of Mg-silicate glasses for models that could elucidate geological and geophysical observations in the crust and mantle of the Earth.

A constitutive analysis of nonlinear shear flow

We analyse shear stress and normal stress data obtained by cone-partitioned-plate (CPP) shear rheometry in recent years. The data sets of Schweizer et al. (Rheol. Acta 47, 943–957, 2008) and Costanzo et al. (Macromolecules 49, 3925–3935, 2016; & Fluids 4, 28, 2019) on nearly monodisperse polystyrene melts and solutions are considered to be among the most reliable shear data available. The Doi-Edwards independent alignment (DEIA) model (J. Chem. Soc., Faraday Transactions 2: Molecular and Chemical Physics 74, 1802–1832, 1978a,b) allows for quantitative description of the steady-state values of shear viscosity eta left(dot{gamma}right) and first normal stress coefficient {psi}_1left(dot{gamma}right) , while it underpredicts the stress overshoot of the stress growth coefficient of the shear stress, η+(t), and fails in predicting a stress overshoot of the stress growth coefficient of first normal stress difference, {psi}_1^{+}(t) . On the other hand, the extended interchain pressure (EIP) model (J. Rheol. 64, 95–110, 2020) provides an excellent prediction of the stress overshoots of both shear stress and first normal stress difference, while overpredicting the steady-state shear viscosity and the first normal stress coefficient. We demonstrate that the shear stress overshoot is the result of a combination of orientational stress overshoot and stretch overshoot, while the normal stress overshoot depends solely on the overshoot of the stretch. Based on these considerations, we propose a novel constitutive approach consisting of a combination of the DEIA and the EIP model, and predictions of this approach are found to be in quantitative agreement with the data sets of Schweizer et al. and Costanzo et al. within experimental accuracy.

Модельная среда с тепловыми и транспортными свойствами жидкой воды

A model of a Frenkel gas-solid medium consisting of Н2О molecules and H3O + and OH- ions with the same density and concentration of particles as liquid water is considered. Particles make a thermal vibrational-diffusive motion, during which they collide, exchange protons and interconvert. Under the assumption that the medium is retained by the dipole-ion interaction forces, it was shown that the evaporation enthalpy H, specific heat C, and also the transport parameters of the medium --- self-diffusion coefficient D, viscosity eta, and thermal conductivity theta --- are close to the reference values ​​for liquid water throughout the interval of its existence (250-600 K).

Dissipative properties and isothermal compressibility of hot and dense hadron gas using non-extensive statistics

We evaluate the transport properties such as shear viscosity (eta ), bulk viscosity (zeta ) and their ratios over entropy density (s) for hadronic matter using relativistic non-extensive Boltzmann transport equation (NBTE) in relaxation time approximation (RTA). In NBTE, we argue that the system far from equilibrium may not reach to an equilibrium described by extensive (Boltzmann-Gibbs (BG)) statistics but to a q-equilibrium defined by Tsallis non-extensive statistics after subsequent evolution, where q denotes the degree of non-extensivity. We observe that eta /s and zeta /s decrease rapidly with temperature (T) for various q-values. As q increases, the magnitudes of eta /s and zeta /s decrease with T. We also show the upper mass cutoff dependence of these ratios for a particular q and find that they decrease with the increase in mass cutoff of hadrons. Further, we present the first estimation of isothermal compressibility (kappa _T) using non-extensive Tsallis statistics at finite baryon chemical potential (mu _B). It is observed that, kappa _T changes significantly with the degree of non-extensivity. We also study the squared speed of sound (c_{s}^{2}) as a function of temperature at finite baryon chemical potential for various q and upper mass cutoffs. It is noticed that there is a strong impact of q and mass cutoff on the behaviour of c_{s}^{2}.

The influence of rare earth ions on the rheological behavior of polyamide

The polyamide 66 (PA66)/lanthanum acetate blends with small amounts of salt loadings (a parts per thousand currency sign 1 wt% of PA) have been prepared in a twin-screw extruder. The rheology of PA66 and its blends has been investigated by a rotational rheometer. The results suggested that with the salt loading in excess of 0.2 wt% the typical Newtonian viscosity plateau disappeared and both the low-frequency complex viscosities eta* and storage modulus G' of blends were much higher than those of neat PA66, the storage modulus was higher than the loss modulus at low frequencies (tan delta GaEuro(3)). While the viscosity followed a strong shear thinning with increasing frequency, the eta* and G' decreased significantly even lower than those of neat PA66 at high frequencies. The combination of dynamic mechanical analysis (DMA) and X-ray photoelectron spectroscopy (XPS) analysis has revealed that coordination effect occurred between lanthanum and carbonyl oxygen atoms in amide groups of the polymer to form pseudocrosslinked network structure, which makes the glass transition temperatures (T (g)) and storage modulus (E') of blends enhanced. The network structure formation-destruction and chains entanglement-disentanglement processes at different frequencies are responsible for the above rheological behaviors of blends.

Numerical models of salt diapir formation by down-building: the role of sedimentation rate, viscosity contrast, initial amplitude and wavelength

Formation of salt diapirs has been described to be due to upbuilding (i. e. Rayleigh-Taylor like instability of salt diapirs piercing through a denser sedimentary overburden) or syndepositional down-building process (i. e. the top of the salt diapir remains at the surface all the time). Here we systematically analyse this second end-member mechanism by numerical modelling. Four parameters are varied: sedimentation rate nu(sed), salt viscosity eta(salt), amplitude delta of the initial perturbation of the sedimentation layer and thewavenumber k of this perturbation. The shape of the resulting salt diapirs strongly depends on these parameters. Small diapirs with subvertical side walls are found for small values of nu(sed) and eta(salt) or large values of delta, whereas taller diapirs with pronounced narrow stems build for larges values of nu(sed) and eta(salt) or small values of delta. Two domains are identified in the four-parameter space, which separates successful down-building models from non-successful models. By applying a simple channel flow law, the domain boundary can be described by the non-dimensional law nu(sedcrit)' = C(1)1/2 delta(0)'rho(sed)'k'(2/)k'(2) + C2, where rho(sed)' is the sediment density scaled by the density contrast Delta rho between sediment and salt, the wavelength is scaled by the salt layer thickness h(salt), and velocity is scaled by eta(salt)/(h(salt)(2)Delta rho g), where eta(salt) is the salt viscosity and g is the gravitational acceleration. From the numerical models, the constants C(1) and C(2) are determined as 0.0283 and 0.1171, respectively.

Kubo Formulas for Second-Order Hydrodynamic Coefficients

At second order in gradients, conformal relativistic hydrodynamics depends on the viscosity η and on five additional "second-order" hydrodynamical coefficients τ(Π), κ, λ₁, λ₂, and λ₃. We derive Kubo relations for these coefficients, relating them to equilibrium, fully retarded three-point correlation functions of the stress tensor. We show that the coefficient λ₃ can be evaluated directly by Euclidean means and does not in general vanish.

Shear viscosity to entropy density ratio in BUU transport model

Shear viscosity (eta) is a basic transport coefficient of the medium. In this work, we calculate shear viscosity to entropy density ratio (eta/S) of an equilibrated system in intermediate energy heavy ion collisions within the framework of the Boltzmann-Uehling-Uhlenbeck model (BUU) model. After the equilibration of Au + Au system at central collision in a fixed volume is reached, temperature, pressure and energy density are extracted by the phase space information and then eta/S is calculated using the Green-Kubo formulas. The results show that eta/S drops with the incident energy and its value is not so drastically different from the RHIC results.

Relationship between the Rheological Properties of Thickener Solutions and Their Velocity through the Pharynx as Measured by the Ultrasonic Pulse Doppler Method

The dependence of the dynamic viscoelastic parameters of carboxymethylcellulose (CMC), xanthan gum, and guar gum solutions on the angular frequency (omega) was compared with that of their viscosity (mu) on the shear rate (gamma). In addition, the effect of these rheological properties on the maximum velocity through the pharynx, V(max), as measured by the ultrasonic pulse Doppler method, was investigated. The CMC and guar gum solutions examined were taken as a dilute solution and a true polymer solution, respectively. The xanthan gum solution was taken as a weak gel above 0.5% and a true polymer solution below 0.2%. The maximum velocity, V(max), of the thickener solutions correlated well with mu, the dynamic viscosity eta', and the complex viscosity eta(*), especially those measured at gamma or omega of 20-30 s(-1) (or rad/s) and above, suggesting that mu, eta', and eta(*) are suitable indexes for care foods of the liquid type for dysphagic patients.

Photophysical Characterization of Benzylidene Malononitriles as Probes of Solvent Friction

Steady-state absorption and emission and femtosecond time-resolved emission spectroscopy of two benzylidene malononitriles, 2-[4-(dimethylamino)benzylidene])malononitrile (DMN) and julolidinemalononitrile (JDMN), are reported in a variety of room-temperature solvents. Solvatochromic shifts of these molecules are consistent with dielectric continuum descriptions and an S(1)-S(0) dipole moment change of 8.5 D. Time-resolved spectra show modest dynamic Stokes shifts of approximately 1000 cm(-1) occurring independently of fluorescence decay, which takes place in 0.5-5 ps in most room-temperature solvents. Absorption transition moments and fluorescence decay times are used to determine radiative rate constants: k(rad) = 0.32 +/- 0.02 ns(-1) in DMN and 0.28 +/- 0.02 ns(-1) in JDMN, assumed to be independent of solvent. Quantum yield data together with these radiative rates provide the reaction rate constants k(rxn) associated with the internal conversion process of these molecules in 33 representative solvents at 298 K and in several solvents as functions of temperature. Reaction rates of JDMN are systematically lower than those of DMN by a factor of 2.0. Values of k(rxn) in series of homologous solvents or in a single solvent at different temperatures are correlated to solvent viscosity eta and temperature T in the manner k(rxn)/T proportional to eta(-p) with exponents 0.2 < or = p < or = 0.8. Solvent polarity appears to influence these reactions such that for a given viscosity reaction in high polarity solvents is significantly slower than in nonpolar solvents. However, this conclusion is predicated on the assumption that reactive friction is identical in solvents of the same viscosity, which is unlikely to be quantitatively correct. The observed reaction rates and their solvent dependence are discussed in terms of isomerization about the C=C bond occurring on a shelf-like potential.

Domain-Growth Kinetic Origin of Nonhorizontal Phase Coexistence Plateaux in Langmuir Monolayers: Compression Rigidity of a Raft-Like Lipid Distribution

The present work addresses the question of a nonhorizontal coexistence plateau found in the liquid-expanded (LE) to liquid-condensed (LC) transition of Langmuir monolayers of lipid amphiphiles, which is apparently incongruent with the first-order character of this main LE/LC phase transition. This pathology is understood in a mechanical context as a resistance of the monolayer against compression giving rise to a nonzero rigidity in the coexistence region. Surface rheology has allowed for a quantitative determination of the compression parameters, namely, dilational elasticity epsilon and viscosity eta. Data for the phase coexistence region reveal dynamical stiffening at faster deformation, which points out a chief control of lipid diffusion on monolayer rigidity. Monolayer viscosity remains however low at the value corresponding to the continuous fluid phase. The presence of coexistence domains is then invoked as the structural element responsible for such a nontrivial rheology, the finite domain growth rate imposing a kinetic limit for equilibrium compression along a quasi-static path. Brewster angle microscopy has allowed for studying the kinetic mechanism for domain growth. The finite rigidity observed at the coexistence region is related to the resistance of LC domains to grow at the expense of the LE phase. A reconciliation of the nonhorizontal plateau observed at finite compression rates with the first-order character of the LE/LC transition emerges then naturally from this kinetic scenario. New mechanical features are consequently assigned to the phase-separated monolayers made of stiff grains rafting in a fluid matrix. Particularly, for a raft-like lipid distribution, we hypothesize a finite rigidity kinetically controlled by the rate of domain growth and a high fluidity controlled by the continuous phase. We have depicted a minimal model of membrane mechanics that accounts for the elasticity of such a heterogeneous composite medium. This "Plum-cake" model is able to qualitatively predict the observed mechanical features and is suggested to describe raft-like membranes as compliant elastic media where lipid domains work as reservoirs able to exchange material with the surrounding fluid phase.

Time-Dependent Compressive Deformation of the Ageing Spine

Mechanical testing of cadaveric spines. To test the hypothesis that, in the ageing spine, vertebrae deform more than discs, and contribute to time-dependent creep. Intervertebral discs and vertebrae deform under load, narrowing the intervertebral foramen and increasing the risk of nerve root entrapment. Little is known about compressive deformations when elderly spines are subjected to sustained physiologic loading. A total of 117 thoracolumbar motion segments, aged 19 to 96 yrs (mean, 69), were subjected to 1kN compressive loading for 0.5, 1, or 2 hours. Deformations during the first 7 seconds were designated "elastic" and subsequent deformations as "creep". A 3-parameter model was fitted to experimental data in order to characterize their viscous modulus E1, elastic modulus E2 (initial stiffness), and viscosity eta (resistance to fluid flow). Intradiscal pressure (IDP) was measured using a miniature needle-mounted transducer. In 17 specimens loaded for 0.5 hours, an optical MacReflex system measured compressive deformations separately in the disc and each vertebral body. On average, the disc contributed 28% of the spine's elastic deformation, 51% of the creep deformation, and 38% of total deformation. Elastic, creep, and total deformations of 84 motion segments in 2-hour tests averaged 0.87, 1.37, and 2.24 mm respectively. Measured deformations were predicted accurately by the model (average r2 = 0.97), but E1, E2, and eta depended on the duration of loading. E1 and eta decreased with advancing age and disc degeneration, in proportion to falling IDP (P < 0.001). Total compressive deformation increased with age, but rarely exceeded 3 mm. When the ageing spine is compressed, vertebral bodies show greater elastic deformations than intervertebral discs, and creep by a similar amount. Responses to axial compression depend largely on IDP, but deformations appear to be limited by impaction of adjacent neural arches. Total compressive deformations are sufficient to cause foraminal stenosis in some individuals.

Tension thickening, molecular shape, and flow birefringence of an H-shaped polymer melt in steady shear and planar extension

Despite recent advances in the design of extensional rheometers optimized for strain and stress controlled operation in steady, dynamic, and transient modes, obtaining reliable steady-state elongational data for macromolecular systems is still a formidable task, limiting today's approach to trial-and-error efforts rather than based on a deep understanding of the deformation processes occurring under elongation. Guided, in particular, by the need to understand the special rheology of branched polymers, we studied a model, unentangled H-shaped polyethylene melt using nonequilibrium molecular dynamics simulations based on a recently developed rigorous statistical mechanics algorithm. The melt has been simulated under steady shear and steady planar extension, over a wide range of deformation rates. In shear, the steady-state shear viscosity is observed to decrease monotonically as the shear rate increases; furthermore, the degree of shear thinning of the viscosity and of the first- and second-normal stress coefficients is observed to be similar to that of a linear analog of the same total chain length. By contrast, in planar extension, the primary steady-state elongational viscosity eta(1) is observed to exhibit a tension-thickening behavior as the elongation rate epsilon increases, which we analyze here in terms of (a) perturbations in the instantaneous intrinsic chain shape and (b) differences in the stress distribution along chain contour. The maximum in the plot of eta(1) with epsilon occurs when the arm-stretching mode becomes active and is followed by a rather abrupt tension-thinning behavior. In contrast, the second elongational viscosity eta(2) shows only a tension-thinning behavior. As an interesting point, the simulations predict the same value for the stress optical coefficient in the two flows, revealing an important rheo-optical characteristic. In agreement with experimental indications on significantly longer systems, our results confirm the importance of chain branching on the unique rheological properties of polymer melts in extension.

Molecular dynamics simulation of cooling: Heat transfer from a photoexcited peptide to the solvent

A systematic molecular dynamics (MD) simulation study of the photoinduced heat transfer from the model peptide N-methylacetamide (NMA) to various solvents is presented, which considers four types of solvent (water, dimethyl sulfoxide, chloroform, and carbon tetrachloride), and in total 24 different force field models for these solvents. To initiate nonstationary energy flow, an initial temperature jump of NMA is assumed and nonequilibrium MD simulations are performed. As expected from simple theoretical models of heat transfer, the cooling process is proportional to the heat capacity C(V) and--to some extent--to the viscosity eta of the solvent. The complex interplay of Coulomb and Lennard-Jones interactions is studied by scaling these interaction energies. The study reveals that realistic changes (< or approximately 10%) of the Lennard-Jones and Coulomb parameters do not change the cooling time considerably. Including polarizibility, on the other hand, appears to enhance the energy dissipation. Moreover, the solvent's internal degrees of freedom may significantly participate in the heat transfer. This is less so for water, which possesses only three high-frequency vibrational modes, but certainly so for the larger solvent molecules dimethyl sulfoxide and chloroform, which possess several low-frequency vibrational modes. For water, the simulated cooling rate is in excellent agreement with experiment, while only qualitative agreement (up to a factor of 2) is found for the other considered solvents. The importance of the force field model and quantum-mechanical effects to correctly describe the cooling process is discussed in some detail.

Graphene: A Nearly Perfect Fluid

Hydrodynamics and collision-dominated transport are crucial to understand the slow dynamics of many correlated quantum liquids. The ratio eta/s of the shear viscosity eta to the entropy density s is uniquely suited to determine how strongly the excitations in a quantum fluid interact. We determine eta/s in clean undoped graphene using a quantum kinetic theory. As a result of the quantum criticality of this system the ratio is smaller than in many other correlated quantum liquids and, interestingly, comes close to a lower bound conjectured in the context of the quark gluon plasma. We discuss possible consequences of the low viscosity, including preturbulent current flow.

Surface tension of room temperature ionic liquids measured by dynamic light scattering

Using dynamic light scattering techniques, we obtained the surface tension sigma, surface excess entropy S(sigma), surface excess enthalpy H(sigma), and viscosity eta for the following seven room temperature ionic liquids in a wide temperature range from 30 to around 140 degrees C: 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-hexyl-3-methylimidazolium hexafluorophosphate, and 1-octyl-3-methyl imidazolium hexafluorophosphate. We have found that sigma increases systematically with decreasing the anion size and the alkyl side chain length. On the other hand, S(sigma) and eta increase with decreasing the anion size but decrease with decreasing the alkyl chain length. H(sigma) seems to decrease with increasing the anion size, but it has no clear dependence on the alkyl chain length. We discuss the bulk and surface properties, referring to the Coulomb interactions and van der Waals interactions.

Impact of Oil Type on Nanoemulsion Formation and Ostwald Ripening Stability

The formation of stable transparent nanoemulsions poses two challenges: the ability to initially create an emulsion where the entire droplet size distribution is below 80 nm, and the subsequent stabilization of this emulsion against Ostwald ripening. The physical properties of the oil phase and the nature of the surfactant layer were found to have a considerable impact on nanoemulsion formation and stabilization. Nanoemulsions made with high viscosity oils, such as long chain triglycerides (LCT), were considerably larger ( D = 120 nm) than nanoemulsions prepared with low viscosity oils such as hexadecane ( D = 80 nm). The optimization of surfactant architecture, and differential viscosity eta D/eta C, has led to the formation of remarkably small nanoemulsions. With average sizes below 40 nm they are some of the smallest homogenized emulsions ever reported. What is more remarkable is that LCT nanoemulsions do not undergo Ostwald ripening and are physically stable for over 3 months. Ostwald ripening is prevented by the large molar volume of long chain triglyceride oils, which makes them insoluble in water thus providing a kinetic barrier to Ostwald ripening. Examination of the Ostwald ripening of mixed oil nanoemulsions found that the entropy gain associated with oil demixing provided a thermodynamic barrier to Ostwald ripening. Not only are the nanoemulsions created in this work some of the smallest reported, but they are also thermodynamically stable to Ostwald ripening when at least 50% of the oil phase is an insoluble triglyceride.

Small-Angle X-ray Scattering and Rheological Characterization of Aqueous Lignosulfonate Solutions

Lignosulfonate is a colloidal polyelectrolyte widely used as a dispersant in various industrial applications and produced during chemical pulping of wood chips. Here we present a systematic small-angle X-ray scattering (SAXS) and rheological study of fractionated lignosulfonate (mass weighted molar mass M w 18 000 g/mol) dissolved in water and 0.2 M NaCl. The concentration range varied from semidilute to concentrated regime. SAXS intensity of all solutions followed the Porod law at all concentrations, which is a clear indication of a compact shape of the lignosulfonate particle. In water, below 10 mass % lignosulfonate, the average interparticle distance obtained from SAXS patterns relates to concentration via a power law with exponent -0.28. Deviation of the power law exponent from ideal -0.33 and a linear decrease in volume fraction normalized Porod constant as a function of concentration are taken as indications of self-association of lignosulfonate. In saline solutions at high lignosulfonate mass fractions the average distance between lignosulfonate particles was longer and the average particle size was larger than those in aqueous solutions. The intrinsic viscosity in saline solution also was larger than that in aqueous solution. Lignosulfonate solutions showed Newtonian viscosity, except at very high concentrations. The variation of the relative zero-shear viscosity eta(0),r) with concentration was interpreted with the Krieger-Dougherty equation. An oblate spheroid shape with an axial ratio of 3.5 describes the average shape of the lignosulfonate particles in saline solutions based on SAXS intensities, the size distribution obtained using gel permeation chromatography, and rheological characterization. The largest dimension of the particles was about 8 nm. SAXS and rheology studies as a function of temperature reveal indications of temperature-dependent self-association.