Rheological Behavior Of Polymer Solutions Research Articles

The role of hyperbranched polyesters in acrylamide‐based polymers as thickening agents in aqueous solutions

AbstractAcrylamide polymers are typically used in industrial and healthcare sectors as thickening agents; however, their thickening capabilities rely mainly in their molecular mass. A versatile and simple strategy to improve their performance is the copolymerization with specific monomers or their chemical modification with structures like dendritic or hyperbranched molecules. This study introduces a novel acrylamide‐acrylic acid polymer grafted with minor proportions (≤4.0 wt%) of Boltorn H30, a hyperbranched polyester monomer. The incorporation of Boltorn H30 aims to exploit the hyperbranched architecture's impact on the viscosity and rheological behavior of polymer solutions. Polymers with 0.4 and 4.0 polyester wt% characterized by several analytical techniques displayed improved viscosity in aqueous solution compared against the parent poly(acrylamide‐co‐acrylic acid). Results revealed that while the molecular mass distribution changed between 20% and 94%, the thickening capabilities significantly improved with increments of 2.7 and 3.8 times compared to that of the original polymers. These findings demonstrate that even with a minimal incorporation of hyperbranched polyesters, the abundance of hydroxyl groups fosters extensive hydrogen bonding, resulting in enhanced viscosity properties of the polymer.

The comparison of interface properties on crude oil-water and rheological behavior of four polymeric nanofluids (nano-SiO2, nano-CaO, GO and CNT) in carbonates for enhanced oil recovery

Nanoparticles (NPs) are currently being used in different areas of petroleum exploration and production, such as drilling, well logging, reservoir management, and enhanced oil recovery (EOR). Nanofluids, prepared from NPs, have been used as a novel flooding for EOR due to the excellent performance in altering interfacial properties and improving rheological behaviors. The properties of nanofluids vary with the structure of nanofluids. Nonetheless, most of the previous studies have focused on a particular type of nanofluid, the interfacial properties of various polymeric nanofluids and their flow behaviors under harsh and challenging reservoir conditions have been rarely reported or compared in literature. In this study, four polymeric nanofluids, prepared by mixing nano-silica (nano-SiO2), nano-CaO, carboxyl functionalized graphene oxide (GO) and amino modified carbon nanotube (CNT) with partially hydrolyzed polyacrylamide (HPAM), were characterized through XRD, FT-IR, UV–Vis and SEM to confirm that the materials were successfully prepared. Then, the colloidal stability, interfacial tension (IFT) reduction, rheological behavior, and wettability on calcite surface of these polymeric nanofluids were also studied in comparison. The experimental results of CNT-NH2/HPAM nanofluid showed that the overlap degree of BS and ΔBS curves was high, oil/brine IFT reduced from 35.84 mN/m to 18.11 mN/m and the contact angle on calcite surface reduced from 139.69° to 47.985°, indicating that the nanofluids were colloidally stability, and both reduce the IFT and alter wettability effectively. Furthermore, the addition of SiO2 and CNT NPs enhanced the network structure significantly, and showed excellent rheological behavior of polymer solution with improved viscoelasticity. Finally, the CNT-NH2/HPAM nanofluid increased the additional oil recovery from 13.8% to 21.6% in core flooding experiments, with the oil displacement mechanism explained in detail. Therefore, the findings of this study can help for better understanding of the effect of NPs on polymeric nanofluids, and set the stage for future investigation into EOR application in carbonate reservoirs.

Effect of [EMIM][BF4] ionic liquid on the properties of ultrafiltration membranes

We employ a miscible mixture of an imidazolium based ionic liquid (IL) and dimethylformamide (DMF) as a good solvent of polyethersulfone (PES) for fabrication of membranes by nonsolvent induced phase separation (NIPS) method. The addition of IL to the cast solution changes solvent quality, which leads to variation of rheological behavior of polymer solution as well as developed membranes performance. We characterize the prepared membranes in terms of water flux, bovine serum albumin (BSA) rejection, pore size, porosity, and water contact angle. Results show that IL influences the kinetics and thermodynamic of phase separation of PES solution. Viscosity values as well as thermodynamic instability of PES solution increase with IL concentration, which lead to higher porosity and pore size of final membranes. Consequently, 17 wt% IL in formulation leads to an increase of mean pore size from 2.0 to 12.7 nm which improves water flux of final membranes from 0.5 to 77 kg/m2h. The results of fouling measurements show that by increasing IL content, the reversible fouling increases. Additionally, the irreversible fouling ratio reduces from 0.42 to 0.28 for 0 and 17 wt% IL containing formulations, respectively. The newly developed membranes provide 97% rejection of BSA solution and can be used as ultrafiltration membranes for the separation and concentration of macromolecules and proteins.

Design of Multifunctional Binder for High-Capacity Silicon Based Anodes

The role of binder material for silicon (Si) and other metal alloy based anodes is critical for their long-term performance. Although several principles have been recognized to fabricate a “better” binder, there seems to be a lack of a rational design and synthesis approach that would meet the robust criteria required for metal alloy anodes. This presentation will discuss the synthesis and characterization of a novel polymer binder, a catechol-functionalized chitosan cross-linked by glutaraldehyde (CS-CG+GA), that serves dual functionalities: a) provides wetness-resistant adhesion capability via catechol grafting and b) possesses mechanical robustness via in-situ formation of a three-dimensional (3D) network. A Si nanoparticle (SiNP) based anode with the designed functional polymer network (CS-CG10%+6%GA) exhibits a capacity retention of 91.5% after 100 cycles (2144 ± 14 mAh/g). This study shows that traditional “better” properties including stronger adhesion strength and higher mechanical robustness do not always improve binder performance, but rather Si anode performance is governed by a delicate synergy of various polymer properties. The clear relationship between grafting density of adhesion groups and degree of crosslinking for ultimate electrochemical performance of polymer binders is established by assessing the rheological behavior of polymer solution, mechanical property of anode coating, adhesion force with SiNPs, peel stress of anode coating, morphology evolution of electrode, and the semi-quantitative evaluation on the scaling behavior and stiffness of the polymer backbone. This study provides a clear path for the rational design of high-performance functional polymer binders for not only Si-based electrodes, but also for other types of alloy and conversion-based electrodes.

Study Rheological Behavior of Polymer Solution in Different-Medium-Injection-Tools.

Previous studies showed the difficulty during polymer flooding and the low producing degree for the low permeability layer. To solve the problem, Daqing, the first oil company, puts forward the polymer-separate-layer-injection-technology which separates mass and pressure in a single pipe. This technology mainly increases the control range of injection pressure of fluid by using the annular de-pressure tool, and reasonably distributes the molecular weight of the polymer injected into the thin and poor layers through the shearing of the different-medium-injection-tools. This occurs, in order to take advantage of the shearing thinning property of polymer solution and avoid the energy loss caused by the turbulent flow of polymer solution due to excessive injection rate in different injection tools. Combining rheological property of polymer and local perturbation theory, a rheological model of polymer solution in different-medium-injection-tools is derived and the maximum injection velocity is determined. The ranges of polymer viscosity in different injection tools are mainly determined by the structures of the different injection tools. However, the value of polymer viscosity is mainly determined by the concentration of polymer solution. So, the relation between the molecular weight of polymer and the permeability of layers should be firstly determined, and then the structural parameter combination of the different-medium-injection-tool should be optimized. The results of the study are important for regulating polymer injection parameters in the oilfield which enhances the oil recovery with reduced the cost.

Polymer flooding for enhanced oil recovery

In this work, Enhanced Oil Recovery methods were studied, with a focus on polymer flooding. Several works were surveyed to verify which parameters most affect the rheological behaviour of polymer solutions. Characteristics of reservoir rocks, important definitions of the oil industry and mathematical models of the rheology of viscous fluids were investigated as well.

Statement of Removal

ABSTRACTChemical flooding is an attractive approach to improve both microscopic and macroscopic sweep efficiencies due to the synergistic effects of interfacial tension reduction and mobility control improvement. In this study, the effect of two hydrophilic silica nanoparticles with different particle sizes of 7 and 25 nm on the phase behavior of surfactant solution and rheological behavior of polymer solution was investigated. Oil recovery experiments for the formulations with high viscosity and low interfacial tension were also conducted in a quarter five-spot glass micromodel. Phase behavior tests indicated that interfacial tension decreased dramatically (0.002 mN/m) due to the presence of smaller dispersed silica nanoparticles in surfactant solution. Rheological experiments showed that larger silica nanoparticles improve the viscosity of low molecular-weight polymer solution more than 20 cP in a wide range of shear rates. Oil recovery experiments revealed that dispersed silica nanoparticles in both surfactant and polymer solutions can improve heavy oil recovery significantly.

An electrorheological investigation of PVB solutions in connection with their electrospinning qualities

During the process of electrostatic spinning, the rheological behaviour of polymer solutions is significantly influenced by the presence of an external electric field. The aim of this contribution is to find a correlation between the electrorheological characteristics of polyvinylbutyral (PVB) solutions and their electrostatic spinnability. When exposed to an external electric field, PVB solutions with either poor or good solvents respond in different ways. It was shown that the complex viscosity ratio ηE*/η0* (where ηE* and η0* represent complex viscosities of a solution in the presence and absence of an external electric field, respectively) can serve as an indicator as to whether a chosen material is a potential candidate for acceptable electrospinning. This occurs when the ratio ηE*/η0* increases with increasing electric field strength, i.e., when poor solvents are applied. The possible changes to the physical and chemical properties of PVB solutions were investigated using SEM, FTIR, DSC, 13C- and 1H-NMR techniques.

Rheology of polymer solutions using colloidal-probe atomic force microscopy

We use colloidal-probe atomic force microscope (AFM) to study the rheological behavior of polymer solutions confined between two surfaces: the surface of a sphere and a flat surface on which the fluid is deposited. Measurements of the hydrodynamic force exerted on the sphere by the flowing liquid allowed retrieving the viscosity of the solution for different distances between the sphere and the flat surface. This method has been experimentally tested for Newtonian fluids for which the viscosity does not vary versus the gap dimensions. On the other hand, for non-Newtonian fluids, such as the large molecular weight polymer solutions used here, the measured viscosity depends on the gap height D between the flat surface and the sphere. The decrease of the viscosity versus gap height is similar to previously observed variations in colloidal suspensions. Depletion of polymers in the gap region due to the high shear rates involved is a possible cause for such a variation.

An Experimental Investigation of Silica Nanoparticles Effect on the Rheological Behavior of Polyacrylamide Solution to Enhance Heavy Oil Recovery

The use of polymer flooding as one of enhanced oil recovery methods has recently increased. The occurrence of high shear rates in reservoir and near well bore through perforation nozzles during polymer flooding cause shear degradation of polymers and therefore polymer viscosity has decreased. Rheological behavior of polymer solution in different conditions of oil reservoir is one of the key factors to develop use of polymer solutions. A few researches are available regarding improving rheological behavior of polymeric solution. In this study, to investigate the effect of nanoparticles on rheological behavior of polymer solutions two samples were prepared: polyacrylamide solution in water and suspension of silica nanoparticles in polyacrylamide solution. The sample viscosities in different shear rates were measured. The best rheology models were developed to state rheological behavior of prepared samples and the measured data were compared to power law model. An increase in the viscosity of the suspension solution with respect to polymer solution in different shear rates was observed. Rheological analysis showed that power law model is a good rheology model to demonstrate rheological behavior of suspension in low and medium shear rates and is an acceptable model for polymer solution in low shear rates. Two types of flooding test were performed in a glass micromodel: flooding by polyacrylamide solution and suspension of silica nanoparticles in polyacrylamide solution. The results of flooding test showed a 10% increase in oil recovery for nanosuspension solution in comparison with polymer solution after one pore volume fluid injection.

A Viscoelastic Polymer Flooding Model Considering the Effects of Shear Rate on Viscosity and Permeability

The present mathematical model for polymer flooding does not consider the elasticity of polymer, and the predictive result differs a lot from the field test value. The authors build a new polymer flooding model considering the viscoelasticity of polymer and the effect of shear rate on resistance coefficient. The elastic viscosity is considered by defining a ratio of elastic viscosity and viscous viscosity. The experiments show that the exponent law model is well characterized the rheological behavior of polymer solutions, as the polymer concentration increases, the power law index n decreases, and the consistency coefficient H increases. There is a logarithmic relationship between residual resistance factor and equivalent shear rate, and the residual resistance factor and the polymer concentration also show a good linear relationship. Those new features are added in chemical flooding software UTCHEM (University of Texas at Austin, Austin, TX) to simulate polymer flooding. The results show that the ultimate recovery of polymer flooding when considering the shear rate and the elastic property is higher than that not considering it.

Rheological behavior of polymer solutions during fabric coating

AbstractThe overall performance of coated products is determined by the intrinsic material properties in solution and processing conditions. To characterize the behavior of these materials, the viscosity of polymers in solution at various concentrations was measured and the experimental data were fitted with the Carreau model. The results describe the rheological behavior of coating materials, and provide a basis for the modeling of polymer flow during the coating process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Two-phase flow in microchannels with surface modifications

Two-phase flows in microchannels with surface modifications are experimentally investigated. First, we investigate the shape of static and moving bubbles in microchannels with square cross-sections for different contact angles. Water and air are mixed on-chip in a cross-shaped mixing chamber. This mixing geometry allows for the production of monodisperse bubbles, the size of which can be controlled with the flow rates. We study the flow morphologies of mixtures made of pure water and air, and made of water with surfactant and air (aqueous foam), in both hydrophilic and hydrophobic microchannels. Second, we investigate the transient rheological behavior of polymer solutions when the length of the polymers is comparable to the height of the channel. The measured viscosity of the solution is several times larger than the expected value, and does not show the typical shear-thinning behavior. These experiments highlight the importance of wall properties for two-phase flows in microfluidic devices.

Contact mechanics studies with the quartz crystal microbalance: origins of the contrast factor for polymer gels and solutions.

A contact mechanics methodology utilizing the quartz crystal microbalance (QCM) has been applied to study the spreading behavior of polymer solutions and gels. Changes in the resonant frequency and in the dissipation are monitored as these materials are brought into contact with the electrode surface of the QCM. The primary application is in studies of elastic polymer gels, where spreading over the surface of the QCM is limited by the elasticity of the gel. Simultaneous measurement of the applied loads and displacements, along with measurement of the QCM/gel contact area, the frequency shift, and the dissipation, enable us to calibrate the QCM as a contact sensor. While changes in the frequency and dissipation both depend linearly on the contact area, measurements of the dissipation provide a more reliable indicator. The relationship between the dissipation and the contact area is determined by the solvent viscosity and by the high-frequency intrinsic viscosity of the system of interest. This result is consistent with previous results on the high-frequency rheological behavior of polymer solutions.

Influence of solvent and polymer sort on anomalous rheological behavior of polymer solution at high dilution

The rheological behavior of polyvinyl acetate (PVAc) in N,N′=dimethylformamide (DMF), methyl ethyl ketone (MEK), 1,2-dichloroethane (DCE), tetrahydrofuran (THF) and toluene (TOL), polystyrene (PS) in DMF, MEK, DCE, THF and cyclohexane (CYH), and random ethylene-vinyl acetate (EVA) copolymer in DCE, TOL, CYH with and without surfactant of Span80 and in the DCE/CYH solvent mixtures with surfactant of Span80 was examined at high dilution. It was shown that the extent and type of the upsweep or downsweep (anomalous rheological behavior) of the reduced viscosity-concentration curves of these different polymers at high dilution are markedly dependent on the dielectric constant of the solvent and the polarity of the polymer used. The experimental results indicated that the anomalous rheological behavior of EVA copolymer, widely used as a flow improver, is related to its efficiency in reducing viscosity and depressing pour point of crude oil and waxy solvents.

Influence of solvent and polymer sort on anomalous rheological behavior of polymer solution at high dilution

Influence of solvent and polymer sort on anomalous rheological behavior of polymer solution at high dilution

Structure and Dynamics of Dilute Polymer Solutions under Shear Flow via Nonequilibrium Molecular Dynamics

We present and discuss results obtained by an extensive nonequilibrium molecular dynamics computer simulation study of polymer solutions under shear, where the chain consists of N beads connected by a finitely extendable nonlinear elastic (FENE) spring force and the solvent is explicitly taken into account. Various scaling laws are extracted from the data which allow one to predict the qualitativeand to certain extent also quantitativestructural and rheological behavior of polymer solutions under good solvent conditions. For most quantities, the results drawn from simulation are compared with experimental data and theoretical predictions which are based on similar models (e.g., harmonic bond potentials or Brownian dynamics methods). Specifically, and in contrast to common theoretical approaches, the simulation yield information about a set of different but characteristic relaxation times, which determine the rheological and structural behavior (for example, flow birefringence, structure factor, rotational dynamics) separately, the difference either resulting from the underlying static or dynamic nature or from relaxation processes which act on different length scales.

Rheooptical Studies of Polydiacetylene Solutions

This work describes a rheooptical experiment with the ability to distinguish between orientation and deformation of polymers while quantifying the degree of deformation in shear using a polymeric chromophore. The chromophore used is poly(4-butoxycarbonylmethylurethane)diacetylene, referred to as 4BCMU, which is known to display varying optical properties that are attributed to conformational changes in the polymer backbone. The orientation may be measured by changes in the extinction coefficient both perpendicular and parallel to the shear field. The results obtained for dilute solutions of 4BCMU under shear are explained by an ellipsoidal random coil polymer in the quiescent state orientating in the shear field. In apparent contradiction to earlier theoretical models, no deformation of the polymer is observed within the range of shear fields used in this work. Extant theories have attributed the rheological behavior of polymer solutions to deformation of the spherical random polymer coils under shear.

1D Simulation of Polymer Flooding Including the Viscoelastic Effect of Polymer Solution

SummarySimple simulation models are constructed to predict the performance of 1D polymer flooding. In the models, two phases of oil and polymer solution were assumed to be immiscible with each other. Because the displacing fluid was non-Newtonian, the BucldeyLeverett equation could be modified and a new approach developed to calculate fractional-flow curves. The rheological behavior of polymer solution was modeled with an Ellis type model and a viscoelastic model. To verify the models, two 1D flooding experiments were carried out on 2.8-cm-diameter, 47-cm-long, unconsolidated cores packed with glass beads (70/100 mesh). Porosities of the cores are about 37% and permeabilities are around 26 μm2. Two white mineral oils of viscosities 25 and 60 mPa·s and a 200-ppm polyacrylamide solution were used. In each experiment, polymer flooding was done after waterflooding. Initial water saturation was controlled to be almost the same at the start of each flood. The calculated polymer-flooding performances were compared with experimental data. The Ellis model predicted earlier breakthrough of polymer solution and lower oil recoveries than the experimental data. On the other hand, the viscoelastic model predicted fractional-flow curves, oil recovery performances, and breakthrough times of the experiments very well. The viscoelastic effect of polymer solution is thought to play an important role in the improvement of oil recovery.

Experimental Determination of the Elongational Viscosity of Polymer Solutions

A comparative study is performed between elongational flow data obtained from fiber spinning and a numerical scheme based on the expressions derived from an anisotropic FENE dumbbell model, with conformation-dependent hydrodynamic friction, coupled with a differential momentum balance made along the spinning filament. Extensional flow data was obtained by using the Gupta-Sridhar extensional viscometer. The test fluid was an aqueous solution of a copolymer of sodium acrylate and acrylamide (Alcomer 120). From the information obtained by this comparison, we assess the influence of preshearing and other factors on the rheological behavior of polymer solutions using this technique.