Polymer Stability in Multiviscosity Engine Oils

Lubricating oil composition for diesel engines with improved fuel consumption and shear stability. The composition contains two comb polymers with different molecular weights. One comb polymer has a lower weight average molecular weight (Mw < 300,000) and the other has a higher Mw (Mw > 400,000). The ratio of these comb polymers in the oil is 0.25 or more. This balance of lower and higher weight comb polymers provides better fuel consumption and shear stability compared to using just one comb polymer. The oil also contains a base oil, other additives like detergents and dispersants, and may further contain pour point depressants, rust inhibitors, extreme pressure additives, and defoamers.

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Enhanced oil recovery (EOR) methods are generally employed in depleted reservoirs to increase the recovery factor beyond that of water flooding. Polymer flooding is one of the major EOR methods. EOR polymer solutions (especially the synthetic ones characterized by flexible chains) that flow through porous media are not only subjected to shearing forces but also extensional deformation, and therefore, they exhibit not only Newtonian and shear thinning behavior but also shear thickening behavior at a certain porous media shear rate/velocity. Shear rheometry has been widely used to characterize the rheological properties of EOR polymer systems. This paper aims to investigate the effect of the polymers concentrations, ranging from 25 ppm to 2500 ppm, on the viscous, linear, and non-linear viscoelastic properties of hydrolyzed polyacrylamide (HPAM) in shear field and porous media. The results observed indicate that viscous properties such as Newtonian viscosity increase monotonically with the increase in concentration in both fields. However, linear viscoelastic properties, such as shear... Read More

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Polymer dynamics are special, in that they are always insensitive to the chemical details of the monomers. However, recent experiments show that the nonlinear extensional rheology of concentrated polymeric liquids has a nonuniversal feature. In this work, the variation of segmental frictional coefficient under flows, which is thought to be the critical factor in explaining the observed nonuniversality, is investigated in the coarse-grained (CG) molecular dynamics (MD) simulations of polymer melts. The frictional coefficients in the simulations are quantified from the expressions we proposed very recently [Jiang, N.; van Ruymbeke, E., Macromolecules 2023, 56 (8), 29112929], which are based on the analytical relationships between the frictional coefficients and the observable rheological and structural properties. After the validation of the simulations with experimental data and our expressions, it is shown that those frictional coefficients can be universally related to the projection areas of the polymer coils in the plane normal to the direction of elongation. Moreover, this proje... Read More

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Lubricating oil composition with high viscosity index, comprising a base oil with a kinematic viscosity of 2.0-7.0 mm2/s at 100°C and a polymer with a specific molecular structure, wherein the polymer has a ratio of peak integral values at 10.0-11.0 ppm to 13.5-14.5 ppm of 0.05 or more as determined by 13C-NMR analysis.

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Abstract This work presents a viscosity model based on the Giesekus equation. The model is shown to be more flexible than the Cross and Carreau models in representing the shear-thinning behavior of viscoelastic fluids. It has been investigated that the influence of the model parameters on the viscosity showed that the mobility parameter plays a distinctive role in adjusting the inflection shape of the viscosity curve. The results show that the new model is able to accurately capture the shear-thinning behavior of polystyrene data, while the Cross and Carreau models tend to underestimate and overestimate the viscosity at the inflection point, respectively. It has been also shown that the Yasuda-type modification is also applicable to the proposed model. Moreover, the viscosity model has been applied to simultaneously fitting a polymeric liquid system and a particulate slurry system. The new viscosity model is a promising tool for modeling the shear-thinning behavior of viscoelastic fluids in a wide range of applications.

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The research presented proposes a new methodology for measuring degradation of polyamide 11 (PA11), as an alternative to the classic criterion established by the American Petroleum Institute in API17TR2. PA11 flexible pipes may be subjected to different degradation conditions, being hydrolysis one of the main aging mechanisms. Aged PA11 pressure barriers coming from flexible pipelines were sliced into inner and outer parts, having a pristine PA11 as a reference. Rheological measurements were performed on air and inert (N2) atmospheres. Mark-Houwink Equation was used to correlate zero-shear viscosity with molecular weight (Mw) and corrected inherent viscosity (CIV). PA11 showed a shear thinning behavior, with higher zero-shear values with the increase in CIV. Cross and power law models were adopted for apparent viscosity behavior prediction purposes with over R2> 90 %. The shifting of the crossover points of elastic (G) and loss modulus (G) showed a correlation with molecular weight and molecular weight distribution (MWD). Based on ColeCole, real () and imaginary () components ... Read More

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Abstract The rheological properties of lubricating greases are determined by the viscosity of the base oil, the interaction between base oil and thickener, and the interaction between thickener particles. The contribution of the oilthickener interactions to the viscosity is well known, but the contribution of the thickenerthickener interactions has not yet been studied by employing theoretical or computational frameworks. In this paper, we use coarse-grained molecular dynamics to simulate a fibrous microstructure, and we show that the experimentally observed viscoelastic/plastic behaviour can be well reproduced. A parametric study shows that the apparent viscosity increases with increasing fibre length, fibre stiffness and thickener concentration. This is as expected, showing that this modelling approach is useful to study effects on grease rheology that are not accessible experimentally, such as impact of fibre entanglement or agglomeration.

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The aging of lubricants is a primary factor contributing to rolling bearing failures. The rolling stability test simulated the aging behavior of grease under shear and high-temperature circumstances. An investigation was conducted on how mechanical-thermal aging impacts the chemical and physical structures of polyurea grease, as well as how changes in thickener microstructure affect rheological and tribological properties. The results show that under shear and high temperature, structural changes in urea lead to a transformation of the thickener morphologies from the growth of entangled ribbon fiber to a large-diameter rod structure, with a significant decrease in the degree of entanglement. When a certain proportion of fibrous and rod structures coexist, the grease has good oil separation capacity, the structural stabilities of grease become weak, and the deformation resistance decreases. During this phase, the polyurea grease has the best tribological performance.

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This study employed Molecular Dynamics (MD) simulations to examine the tribological impact of polyalkylmethacrylate (PAMA), a polar lubricant additive known for its role as a Viscosity Index (VI) improver, when combined with the non-polar lubricant polyalphaolefin (PAO) 6. Examining the solid-lubricant interface in a confined liquid between iron surfaces with a Couette flow, the research delves into molecular interactions, emphasizing mechanisms governing wall slip for both non-polar and polar molecules.Notably, for non-polar molecules, a singularity in slip length is observed with a molecular-scale gap height resulting in an infinite slip length.However, the addition of polar additives eliminates slip, leading to increased friction.Furthermore, in terms of bulk shear, the introduction of polar additives reduces shear thinning as temperature increases.This dual observation highlights the substantial impact of polar additives on both wall slip behavior and bulk shear properties in the lubricant system.

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Under the parameters of normal engine operation, lubricating oil typically experience periodic shifts in its viscosity. Because of this, engine oils often include polymeric additives that are referred to as viscosity modifiers. The oil is able to give acceptable fluid lubrication at extreme temps due to these additives, which are oil-soluble polymers. The aim of present work to use polymers in form of nano-composites such as Styrene, Octadecyl-methacrylate (ODMC) and Dodecyle-methcrylate (DDMC) for lube oil viscosity index and pour point enhancement during copolymerization reaction. The benzoyl peroxide was used as an initiator. Solubilizes were made using SN-150 mineral base oil from the Al-Dorha refineries in Baghdad, which had a viscosity index of 128, and a viscosity range of 0 to 100C. Styrene and methacrylate monomer combinations were copolymerized in an SN-150 mineral base oil solution in a nitrogen atmosphere at 60-80C. A 200 mm3 oil glass reactor fitted with a magnetic stirrer and a reflux condenser was used to conduct the reactions. Five percent by weight of the total mon... Read More

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Addition of particles to a viscoelastic suspension dramatically alters the properties of the mixture, particularly when it is sheared or otherwise processed. Shear-induced stretching of the polymers results in elastic stress that causes a substantial increase in measured viscosity with increasing shear, and an attractive interaction between particles, leading to their chaining. At even higher shear rates, the flow becomes unstable, even in the absence of particles. This instability makes it very difficult to determine the properties of a particle suspension. Here, we use a fully immersed parallel plate geometry to measure the high-shear-rate behavior of a suspension of particles in a viscoelastic fluid. We find an unexpected separation of the particles within the suspension resulting in the formation of a layer of particles in the center of the cell. Remarkably, monodisperse particles form a crystalline layer which dramatically alters the shear instability. By combining measurements of the velocity field and torque fluctuations, we show that this solid layer disrupts the flow instabi... Read More

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Abstract Shear viscosity and elasticity have been identified as two of the most influential factors controlling the volume of drilling fluid invasion into reservoir and the resultant formation damage. Past studies were inconclusive regarding individual effects of fluid shear viscosity vs elasticity, as it was challenging to disintegrate and measure their impacts independently. Therefore, we investigated the relative contributions of the fluid shear viscosity and the elasticity on the fluid invasion and the resultant productivity impairment. 24 water-based drilling fluids were prepared using various blends of three different molecular weight PHPA polymers. Detailed rheological characterizations of these fluids were carried out by conducting amplitude sweep and controlled shear rate tests. Viscoelastic properties of the fluids were quantified in terms of energy dissipation, which physically signifies the amount of energy required per unit volume to cause an irreversible deformation in the fluids internal structure. Static filtration tests and core flooding experiments were conducted t... Read More

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In this paper, the two-dimensional KelvinHelmholtz (KH) instability occurring in the shear flow of polymer fluids is modeled by the dissipative particle dynamics (DPD) method at the coarse-grained molecular level. A revised FENE model is proposed to properly describe the polymer chains. In this revised model, the elastic repulsion and tension are both considered between the adjacent beads, the bond length of which is set as one segments equilibrium length. The entanglements between polymer chains are described with a bead repulsive potential. The characteristics of such a KH instability in polymer fluid shear flow can be successfully captured in the simulations by the use of the modified FENE model. The numerical results show that the waves and vortexes grow more slowly in the shear flow of the polymer fluids than in the Newtonian fluid case, these vortexes become flat, and the polymer impedes the mixing of fluids and inhibits the generation of turbulence. The effects of the polymer concentration, chain length, and extensibility are also investigated regarding the evolution of KH i... Read More

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The rheology problems of non-Newtonian oil, accompanied by the physical phenomena of formation and destruction of coagulation structures and aggregates, significantly affecting the flow are considered and analyzed. Also are considered issues of hydrodynamic interaction of particles leading to the formation of disordered structures, which significantly change the rheological properties of non-Newtonian oil. It has been noted that the formation of coagulation structures depends on energy dissipation, viscosity, stress or shear rate, and the size of the particles forming the structure. With increasing asphalt-resin content in the oil, the probability of particle collision increases, increasing the rate of formation of various disordered structures up to a framework that nullifies the rate of oil flow. Applied problems of rheology, including dissolution kinetics of asphalt-resinous substances in aromatic hydrocarbons and improving rheological properties of the oil, rheology of structured non-Newtonian oils in gas lift method of production, as well as possible ways to create new technolog... Read More

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In order to help one to judge the friction properties of lubricating oils without tests, this paper intends to establish the correlation between the characteristic parameters of lubricating oils and the friction properties. The elastohydrodynamic and boundary friction properties of poly alpha olefin (PAO) synthetic oil, polyol ester oil and paraffin-based mineral oil were tested using a Mini-Traction Machine. Fourier transform infrared microscopy is used to identify material changes before and after friction tests. The kinematic and dynamic viscosities of the three lubricating oils were measured using a petroleum product viscosity tester and a rotating rheometer. The results show that the kinematic viscosity does not directly determine the COF (coefficient of friction) of the lubricating oil, but the higher the dynamic viscosity, the higher the COF of the lubricating oil. The higher the viscosity-pressure coefficient, the lower the viscosity index (the worse the viscosity-temperature performance), and the higher the COF of the lubricating oil, which is related to the adaptability of ... Read More

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Viscous and elastic behaviors of the crude oil-polymer emulsions were studied experimentally through Creep-recovery investigation. Two different types of polymers of Alcoflood and Xanthan were investigated in this study to represent the synthetic and bio-polymers. A Rheostress RS100 in controlled stress CS-mode was utilized to carry out all the experimental results and assessments. The viscous and elastic investigations of the crude oil-polymer emulsions were examined for polymer concentrations of 0104 ppm, 075% by volume of crude oil, and two candidates of each polymer. This experimental study resulted that the polymer and crude oil concentrations exhibited significant impact on the compliance behavior. For polymer concentrations higher than 103 ppm, the crude oil-Xanthan emulsions exhibited higher recovery% than the oil-Alcoflood emulsions. The ability of the Xanthan gum to form elastic characteristic within the crude oil emulsion is higher than the Alcoflood polymer material.

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The shear rheology of particle suspensions in shear-thinning polymeric fluids is studied experimentally using parallel plate measurements and numerically using fully resolved, 3D finite volume simulations with the Giesekus fluid model. We show in our experiments that the steady shear viscosity and first normal stress difference coefficient of the suspension evolve from shear-thickening to substantially shear-thinning as the degree of shear-thinning of the suspending fluid increases. Moreover, in highly shear-thinning fluids, the suspension exhibits greater shear-thinning of the viscosity than the suspending fluid itself. Our dilute body-fitted simulations show that in the absence of hydrodynamic interactions, shear-thinning can arise from the particle-induced fluid stress (PIFS), which ceases to grow with increasing shear rate at low values of (solvent viscosity ratio) and finite values of (the Giesekus drag coefficient). In a Giesekus suspending fluid, the polymers surrounding the suspended particle are unable to stretch sufficiently at high Weissenberg numbers (Wi) and the redu... Read More

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This review is devoted to understanding the role of elasticity in the main flow modes of polymeric viscoelastic liquidsshearing and extension. The flow through short capillaries is the central topic for discussing the input of elasticity to the effects, which are especially interesting for shear. An analysis of the experimental data made it possible to show that the energy losses in such flows are determined by the Deborah and Weissenberg numbers. These criteria are responsible for abnormally high entrance effects, as well as for mechanical losses in short capillaries. In addition, the Weissenberg number determines the threshold of the flow instability due to the liquid-to-solid transition. In extension, this criterion shows whether deformation takes place as flow or as elastic strain. However, the stability of a free jet in extension depends not only on the viscoelastic properties of a polymeric substance but also on the driving forces: gravity, surface tension, etc. An analysis of the influence of different force combinations on the shape of the stretched jet is presented. The con... Read More

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Polymer flooding is one of the techniques used to enhance oil recovery from depleted hydrocarbon reservoirs. Although this technology is popular for this application, the shearing effect in the injection process causes poor performance, which is an obstacle to meeting the needs of the formation. An experimental evaluation of the rheological properties, viscoelasticity, hydrodynamic size, static adsorption, and seepage characteristics of the associated polymer solution before and after shearing was conducted to determine the influence of shearing on the polymer solution. The results show that the effect of shear on the polymer was irreversible, and the properties of the polymer solution damaged by shear were attenuated. After the critical associating concentration, the associated polymer can recover its solution properties through hydrophobic association, which can improve the shear resistance of the polymer solution and make its own rheological law and reduce the viscoelastic change. Although the hydrodynamic size, viscoelasticity, and adsorption capacity of the polymer solution afte... Read More

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Polymer additives in lubrication oils are known to play a role as viscosity index improvers that change the temperature dependence of viscosity. On the other hand, it is assumed that polymers adsorbed on surfaces contribute to low friction, and clarification of their mechanical properties and temperature dependence is essential for lubrication design. In our previous research, we have successfully measured the gap dependence of mechanical properties (shear viscoelasticity) of base oils by applying the fiber wobbling method (FWM), a nano-rheological measurement method that we originally developed. In this study, we developed a temperature-control stage for FWM to measure the temperature dependence of shear viscoelasticity in nano-gaps of polymer-added lubricants.

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Amphiphilic polymers represent significant ability in emulsifying crude oil during the displacement, enabling effective control the oil/water interface mobility and reduction of heavy oil viscosity. Herein, an amphiphilic polymer, named PMC16, was copolymerization using by hydrophobic monomer C16DMAAC, along with acrylamide and acrylic acid as comonomers. The structure of PMC16 was identified by 1H NMR, and FT-IR. The potential of PMC16 for oil recovery enhancement was evaluated through assessments of fluid viscoelasticity, reduction in oil viscosity, wettability alternation and interfacial activity between heavy oil and PMC16. The results reveal that PMC16 showed well shear resistance due to the hydrophobic association between its molecular chains. In addition, the PMC16 can effectively decrease the viscosity of the oil phase through emulsification. The viscosity reduction achieved by PMC16 for heavy oil surpasses 95% under the condition of 60 C, oilwater ratio of 3:7 and a concentration of 3000 mg/L. Additionally, PMC16 solution induces a shift in the wettability of solid surface... Read More

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We prove conditions for global nonlinear stability of Oldroyd-B viscoelatic fluid flows in the Couette shear flow geometry. Global stability is inferred by analysing a new functional, called a perturbation entropy, to quantify the magnitude of the polymer perturbations from their steady-state values. The conditions for global stability extend, in a physically natural manner, classical results on global stability of Newtonian Couette flow.

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In a confined simple shear flow, the macromolecules of a polymeric liquid reorient near the walls so that the measured viscosity decreases. For instance, in a small-amplitude oscillatory shear flow, the real part of the complex viscosity decreases with confinement, and macromolecular orientation explains this. These effects in oscillation have been explained analytically for a rigid dumbbell suspension and, for a confined small-amplitude oscillatory shear flow, the summation coefficients have been determined. By contrast, for the confined steady shear flow, the summation coefficients are undetermined. In this paper, we determine these coefficients and use them to evaluate the steady shear (i) viscosity and (ii) normal stress coefficients for a rigid dumbbell suspension. We find that the zero-shear viscosity and the zero-shear first normal stress coefficients decrease with confinement. We further find that the dimensionless (i) steady shear viscosity curve increases with confinement and (ii) first normal stress coefficient first decreases with light confinement and then increases with... Read More

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Understanding the nonequilibrium dynamics of topologically entangled polymers under strong external deformation has been a grand challenge in polymer science for more than half a century. Important deformation-induced single-polymer structural changes have been identified, such as chain orientation and stretching. But how these changes impact the physical entanglement network and bulk viscoelasticity remains largely elusive in the fast flow regime that involves highly oriented and stretched polymer chains. Here, through new experimental and theoretical developments, we establish a unified understanding of the steady-state shear viscosity, , of entangled polymer melts at high Rouse Weissenberg numbers, WiR > 1. New capillary rheometry measurements in the absence of flow instabilities reveal a dramatic change in shear-thinning scaling from 0.7 0.1 at WiR < 1 to (N/)0.50 at WiR > 1, where N is the degree of polymerization and is the shear rate. Moreover, the viscosity scaling exponent with polymer molecular weight decreases with applied shear stress, and a remarkable ... Read More

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In the study of polymer flooding, researchers usually ignore the genetic stress properties of viscoelastic fluids. In this paper, we investigate the process of viscoelastic fluid flooding the remaining oil in the dead end. This work uses the fractional-order Maxwell in the traditional momentum equation. Furthermore, a semi-analytic solution of the flow control equation for fractional-order viscoelastic fluids is derived, and the oil-repelling process of viscoelastic fluids is simulated by a secondary development of OpenFOAM. The results show that velocity fractional-order derivative significantly affects polymer solution characteristics, and increasing the elasticity of the fluid can significantly improve the oil repelling efficiency. Compared to the Newtonian fluid flow model, the fractional order derivative a and relaxation time b in the two-parameter instanton equation can accurately characterize the degree of elasticity of the fluid. The smaller the a, the more elastic the fluid is and the higher the oil-repelling efficiency. The larger the b, the less elastic the fluid is and ... Read More

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To study the migration conditions of film-like microscopic residual oil, microscopic visualization flooding experiments and Polyflow numerical simulations were conducted. Furthermore, we calculated the adhesion work of oil displacement systems and cores under different conditions. The results revealed that polymer flooding relies on an increase in the horizontal stress differential for systems with film-like residual oil. The results also indicated that a higher viscosity of the polymer corresponds to a larger contact angle with the core and a smaller amount of adhesion work. Additionally, with a lower interfacial tension of the alkalisurfactantpolymer (ASP) system, the contact angle with the core is smaller, and the amount of adhesion work is larger. Under the same viscosity conditions, weaker interfacial tension corresponds to a larger deformation amplitude, larger advancing angle, and smaller receding angle. Under the same interfacial tension conditions, as the viscosity of the displacement fluid increases, the deformation amplitude of the oil film increases, the advancing angle... Read More

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Summary Polymer degradation is detrimental to enhanced oil recovery (EOR) because it ultimately leads to solution viscosity loss. Molecular breakage during flow owing to high stresses, known as mechanical degradation, can occur in numerous stages during field polymer injection. One of the reasons biopolymers are promising for EOR is their enhanced mechanical stability compared to their polyacrylamide counterparts. This study presents a comparative investigation of the mechanical degradation of biopolymers with potential applications in EOR. The mechanical degradation was evaluated by flowing the solutions through a short-length capillary (internal diameter of 0.127 mm and length of 10 mm) and then testing their viscosity loss through a rheometer. Nine flow velocities were tested between 0.13 and 66 m/s (shear rates between 8.29 103 and 1.66 107 s1) in addition to the undegraded baseline. Four biopolymers were evaluated [xanthan gum (XG), scleroglucan (SCLG), schizophyllan (SCP), and guar gum (GG)] and compared to two polyacrylamides [hydrolyzed polyacrylamide (HPAM) and HPAM-AMP... Read More

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Abstract Drilling fluids for oilfield use consist of complex mixtures of natural and synthetic materials. The viscous properties along with the particle size distribution of the applied weight materials are vital in controlling the stability of the microstructure and density of the drilling fluid. Typical oil-based drilling fluids made for North Sea oilfield drilling application with oilwater ratios (OWRs) of 80/20 and 60/40 are examined with respect to their density stability. The stability was analyzed at both rest and dynamic conditions using flow and viscosity tests, oscillatory sweep tests, creep tests, and time-dependent oscillatory sweep tests using a scientific rheometer with a measuring system applying a grooved bob at atmospheric conditions. The quantities used in ranking the stability of the fluids include the yield stress, flow transition index, mechanical storage stability index, and dynamic sag index. We observed that the drilling fluid sample with OWR = 60/40 showed a more stable dispersion with a stronger structure having higher yield stress and flow transition index... Read More

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Oil undergoes temporary viscosity changes under operating conditions in engines. Therefore, engine oils usually contain polymeric additives called viscosity modifiers. These additives are oil soluble polymers; enable the oil to provide adequate hydrodynamic lubrication at high temperatures and good starting/pumping performance at low temperatures. Pour point depressants are additives which add to engine oil to lower/decrease the probability of wax argument formation under lower temperature conditions. The aim of this chapter is to present the historical synthesis of different types of acrylic polymers, there effect as lubricating oil additives (viscosity index improvers and pour point depressants). In addition, the mechanisms by which viscosity modifiers and pour point depressants work, and method of evaluation.

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The structure and flow behavior of lubricating greases depend on the base oil and the type and concentration of the dissolved thickener. In this study, the linear viscoelastic properties of greases were characterized by combining oscillatory shear and squeeze flow covering a broad frequency range (0.1105 rad s1). Multiple-particle tracking (MPT) microrheology and scanning electron microscopy (SEM) provided further insight into local viscoelastic properties and sample structure on a submicron-length scale. The type and viscosity of the base oil did not affect the absolute value of the complex viscosity and the filament shape formed by a given thickener. High-frequency shear modulus data, however, indicated that the thickener lithium 12-hydroxystearate formed stiffer networks/filaments in poly--olefins than in mineral oils. As expected, the viscosity increased with increased thickener concentrations, but microscopy and high-frequency rheometry revealed that the thickness, length, and stiffness of the individual filaments did not change. In mineral oil, the 12-hydroxystearate thicken... Read More

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Polymer viscosity is an important thing to study in rheology. Empirical and mathematical approaches must be carried out to determine the mechanism that occurs in the polymer when it enters the melting zone. We know that polymers are non-Newtonian materials when they enter the melting transition region. However, another unique characteristic related to the viscosity of the polymer makes the polymer a superior material according to its application. Therefore, in this paper, we will briefly review Newtonian and non-Newtonian approaches to polymer viscosity. Maybe this paper can help become a reference for further applications in materials that have flowing properties.Keywords: polymer, viscosity, non-Newtonian, Newtonian

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Nonlinear shear and elongational rheology of entangled poly(propylene carbonate) (PPC) melts having different molecular weights with relatively narrow molecular weight distribution are examined. In shear measurements, the PPCs exhibit a typical shear thinning behavior with stress overshoot at high shear rates. In the shear rate dependence of the steady-state viscosity, the PPCs do not violate the empirical Cox-Merz rule, which is known to be valid for many other entangled polymer melts. In uniaxial elongational measurements, the viscosity growth functions of the PPCs show a weak deviation from the linear viscoelastic (LVE) envelope to the higher side at the high Weissenberg number Wid (=d, where is the elongation rate and d is the characteristic disengagement time). The steady-state viscosity of the PPCs shows an elongational thinning as a function of 0.5 within an error. These results are similar to some other polymer melts such as polystyrene (PS). In addition, the normalized elongational viscosity growth functions of PPC and PS with a similar entanglement number Z, are com... Read More

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A lubricating oil composition for automobile transmissions that achieves excellent shear stability, temperature viscosity properties, and low-temperature viscosity properties. The composition comprises a lubricant base oil and a liquid random copolymer of ethylene and α-olefin prepared by solution polymerization under a specific catalyst system. The copolymer has a molecular weight distribution that balances shear stability with temperature viscosity properties, enabling the composition to maintain its viscosity and lubricating performance over a wide temperature range.

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Four commercial viscosity index improvers (VII) have been used to investigate the behavioral differences of these compounds in three types of universally applicable base oils. The used VIIs are structurally three types of co-polymer: ethylene-propylene, star isoprene, and two di-block styrene-isoprene. After dissolving of different amounts of VIIs in different base oils, the kinematic viscosities at two standard temperatures were determined and the intrinsic viscosities were calculated according to Huggins method, then the effects of changes in base oil and polymer type were investigated. Intrinsic viscosities as criteria for polymer molecules sizes were found to be higher at lower temperature than at higher temperature. Dependence of intrinsic viscosity on the polymer molecular weight was observed. In the previous works, one or two types of VIIs were studied in only one type of base oil and/or solvent, not different base oils. Furthermore, different ranges of temperatures and concentrations not necessarily applied ranges were selected, but in this work, common base oils and most com... Read More

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This article discusses the pecularities of chemistry and architecture of polymers modern viscosity modifiers of engine oils, the proposed mechanism of their action, influence the rheological, dispersing properties, energy- and resource saving propertiesof engine oils. The quality scores such as tightening efficiency and shear stability and concepts of permanent and temporary viscosity loss are considered. The short charachteristics of the bench test methods of polymers shear stability conserns.

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Amphiphilic polymers can emulsify with crude oil to form and stabilize oil in water emulsion due to existence of hydrophobic groups, so as to improve the dispersion effect of crude oil. Supramolecular system is constructed by electrostatic interaction between amphiphilic polymer and polybasic acid, which may affect the interaction between hydrophobic groups and crude oil. Whether stable emulsion can be formed, and effect of polybasic acid structure on the stability of crude oil emulsion needs to be further studied. The effect of polybasic acid on the stability of the emulsion was studied by bottle test and stability analyzer. Furthermore, particle size analysis, interfacial tension analysis, interfacial rheological analysis, dynamic rheological characteristics analysis and visual rheology test were used to study the emulsification law of supramolecular crude oil and the action mechanism of stable emulsion. The results show that emulsion stability of different amphiphilic polymer supramolecular systems is mainly affected by interfacial tension, external phase structure strength and dr... Read More

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Viscosity index (VI) and shear stability index (SSI) are standard methods used in the lubricant industry to determine temperature-viscosity dependency and resistance to product degradation, respectively.A variety of oil-soluble polymers, including poly(alkyl methacrylates) (PAMAs) are routinely used to control these properties in fully-formulated liquid lubricants.In this report, we use reversible addition-fragmentation chain transfer (RAFT) polymerization to precisely target identical degrees of polymerization in a family of PAMAs with varying lauryl, hexyl, butyl, ethyl, and methyl groups.Then, expanding on previous methodology reported in the literature, we establish structure property relationships for these PAMAs, specifically looking at how intrinsic viscosity [] and Martin interaction parameters K M relate to VI and SSI characteristics.While the intrinsic viscosity [] is associated with the volume of macromolecules at infinite dilution, the parameter K M reflects the hydrodynamic interactions of polymer chains at actual polymer concentrations in lubricating oils.In this pape... Read More

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The engine oil contains various performance additives along with polymer-based viscosity index improver, which are made from special types of flexible long chain polymers whose functionality is derived from their thickening efficiency, viscosity-temperature relationship, and shear stability. Olefin copolymers of the type ethylene/propylene copolymer are extensively used as viscosity index improver for engine oil formulations whose performance is a function of their composition, co-monomer sequence distribution and molar mass. Polymer coils interact with base oil and make it increasingly resistant to flow which accounts for substantial changes in viscosity parameters i.e. kinematic viscosities and viscosity index of blended base oils. Intrinsic viscosity of a polymeric solution is an important dilute solution viscosity parameter, which is easily measurable using Ubbelohde viscometer. In the present work, intrinsic viscosity of twenty samples of laboratory synthesized olefin copolymer in cyclohexane at 30 C were correlated with their thickening efficiencies, kinematic viscosities of... Read More

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Turbulent drag can be reduced by the use of anti-turbulent additives, which are often associated with significant economic benefits. For half a century turbulent drag reduction has become a hot research topic. However, under the strong hydrodynamic force of turbulent flow, chains of the polymers macromolecules may undergo significant mechanical degradation. In the present work, we investigated drag reduction and mechanical degradation characteristics of oil-soluble polymer-polyalphaolefin (PAO) in turbulent flows in a parallel-plate disk rheometer, cylindric rotational rheometer, and commercial oil pipeline. The influence of Reynolds number, temperature, polyalphaolefin composition, and concentration on polymer mechanical degradation have been analyzed. We revealed different degradation behaviors in turbulent flows for oil-soluble polymers in rheometer and pipeline. A degradation law for oil-soluble polymers in a rheometer and a general model of degradation in the pipeline have been derived, which can be used to predict drag reduction efficiency DR and effective polymer concentratio... Read More

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The Oldroyd-B model has been used extensively to predict a host of instabilities in shearing flows of viscoelastic fluids, often realized experimentally using polymer solutions. The present review, written on the occasion of the birth centenary of James Oldroyd, provides an overview of instabilities found across major classes of shearing flows. These comprise (i) the canonical rectilinear shearing flows including plane Couette, plane and pipe Poiseuille flows; (ii) viscometric shearing flows with curved streamlines such as those in the TaylorCouette, cone-and-plate and parallel-plate geometries; (iii) non-viscometric shearing flows with an underlying extensional flow topology such as the flow in a cross-slot device; and (iv) multilayer shearing flows. While the underlying focus in all these cases is on results obtained using the Oldroyd-B model, we also discuss their relation to the actual instability, and as to how the shortcomings of the Oldroyd-B model may be overcome by the use of more realistic constitutive models. All the three commonly used tools of stability analysis, viz., ... Read More

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It is generally understood that for entangled viscoelastic polymer solutions entanglement effects are significantly weakened under strong flow. In recent years, it has been observed that, despite quiescently being entangled at use concentrations, high molecular weight HPAM solutions are characterised by their Rouse time when transitioning to elastic turbulence in porous flow. Whereas this has been inferred, for these practically important solution polymers direct measurement of the apparent characteristic relaxation time under shear has not been reported. Here we use controlled-stress parallel-superposition background shear to assess the apparent characteristic relaxation time as a function of shear rate. Our results coincide with a recently reported calculation using Rolie-poly and Rolie-double-poly models.

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Poly-surfactant is a new type of oil displacing agent, which is grafted on polymer molecular chain and has special function group. Through the interaction of inter-molecular chain and intra-molecular chain, that can achieve the functions of emulsifying, increasing viscosity, washing oil, plugging water, etc. Laboratory study shows that poly-surfactant has EOR over 18% than water flooding. In this paper, the physical and chemical properties of the series of poly-surfactant were evaluated by laboratory test. The viscosity-increasing property of the poly-surfactant was much better than that of the common polymer and it was a shear-diluting fluid. The retention rate of viscosity in 60 days is higher than 100%, and the retention rate of viscosity in Profile Control and 70 mpa.s, and the water-out rate of emulsion is between 30% and 70%. It can provide a technical support for greatly EOR in thin and poor reservoirs in terrestrial multi-layered sandstone reservoir.

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High molecular polyacrylamides have been used widely in polymer flooding applications for improving oil production. The injected polymer is subjected to different shear rates and thus results in various performance. This paper integrates the behaviors of different laboratory experiments into a general workflow for evaluation of the impact of shear rate on oil production using numerical simulation. The impact of shear rates on the rheological property of a polymer solution was evaluated by injection of polymer solution into a core plug at different injection rates. The measured bulk viscosity and calculated apparent viscosity were fitted with different rheological models to identify flow behavior and the corresponding shear rate range. Shear rate at sand surface and shear rate profile from injector to deep formation were estimated using an inverted five-spot well pattern. Combination of the experimental results with the estimated shear rates was used to describe the flow behaviors of injected polymer solutions. The impact of shear-rate dependent viscosity on oil production was evaluat... Read More

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Enhanced oil processing aims to retrieve petroleum fluids from depleted reservoirs after traditional processing. Hydrogels and polymeric macromolecules are considered effective displacing agents in oil reservoirs. In the current work, the authors used hydrophilic hydrogels based on poly(ethylene glycol)/poly(propylene glycol) (PEG/PPG) surfmers for oil displacement processes. Statistical modeling of the rheological properties at 80 C for the two hydrogels indicates that the viscosity-shearing profile obeys the power-law model. Also, shear stress scanning follows the Herschel-Bulkley and the Bingham plastic models. The two hydrogels exhibit an initial yield stress owing to the formation of a three-dimensional (3D) structure at zero shearings. Furthermore, PEG and PPG hydrogels can retain the viscosity after a shear rate of 64.68 S

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A lubricating oil composition for automatic transmissions that balances performance and durability. The composition comprises a blend of low-viscosity base oils, including Fischer-Tropsch synthetic oils and other low-viscosity oils, and a high-viscosity base oil, typically an olefin copolymer. The blend is formulated to achieve a specific viscosity range, viscosity index, and flashpoint, while maintaining shear stability and minimizing evaporation. The composition is suitable for use in automatic transmissions, including torque converters, wet clutches, gear bearing mechanisms, and hydraulic mechanisms.

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In this work, the recently proposed frame-invariant Generalized Newtonian Fluid (GNF) constitutive equation [M. Zatloukal, Frame-invariant formulation of novel generalized Newtonian fluid constitutive equation for polymer melts, Phys. Fluids 32(9), 091705 (2020)] has been modified to provide uniaxial extensional viscosity at a high strain rate limit corresponding to molecular expression for a fully extended Fraenkel chain reported in Ianniruberto et al. [Melts of linear polymers in fast flows, Macromolecules 53(13), 50235033 (2020)]. It uses basic rheological and molecular parameters together with the ratio of monomeric friction coefficients for equilibrium and fully aligned chains. The modified GNF model was successfully tested by using steady-state uniaxial extensional viscosity data for well-characterized entangled polymer melts and solutions [namely, linear isotactic polypropylenes, poly(n-butyl acrylate), polyisoprenes, and polystyrenes] covering a wide range of strain rates, including those, at which the chain stretch occurs. Only two fitting parameters were sufficient to ... Read More

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A lubricating composition for internal combustion engines that provides improved fuel economy and wear protection. The composition comprises a low-viscosity base oil, a functionalized ethylene-alpha-olefin copolymer, and a poly(meth)acrylate polymer. The functionalized copolymer contains an acyl group grafted with a hydrocarbyl amine, and the poly(meth)acrylate polymer is a block or tapered block copolymer with a first block insoluble in the base oil and a second block soluble in the base oil. The composition maintains good high-temperature viscosity and exhibits excellent performance in the DW10 Lash Adjuster Test, a standard test for engine wear protection.

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Whereas much is known about the complex viscosity of polymeric liquids, far less is understood about the behavior of this material function when macromolecules are confined. By confined, we mean that the gap along the velocity gradient is small enough to reorient the polymers. We examine classical analytical solutions [O. O. Park and G. G. Fuller, Dynamics of rigid and flexible polymer chains in confined geometries. II. Time-dependent shear flow, J. Non-Newtonian Fluid Mech. 18, 111122 (1985)] for a confined rigid dumbbell suspension in small-amplitude oscillatory shear flow. We test these analytical solutions against the measured effects of confinement on both parts of the complex viscosity of a carbopol suspension and three polystyrene solutions. From these comparisons, we find that both parts of the complex viscosity decrease with confinement and that macromolecular orientation explains this. We find the persistence length of macromolecular confinement, Lp, to be independent of both and 0.

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To describe the viscosity of oil, the author proposed a theory based on a new physical model, which takes into account the interaction of individual colloidal particles and their aggregates of fractal structure. This process is accompanied by the addition of individual particles to aggregates and by their separation under the action of shear stress, which is reflected in the energy consumption of the fluid movement and manifests itself as a dependence of the viscosity on the shear rate. The purpose of the review is to demonstrate the application of fractal viscosity theory to interpret the results of known experimental studies. The review also contains the results of new experimental studies of a model sample of oil to illustrate a number of statements of the theory. The detailed parameters of the physical model are specified, on the basis of which a fractal theory of viscosity is proposed; a system of two equations is obtained that allows to describe the dependence of viscosity on the shear rate and time. It is demonstrated that the conclusions drawn from the theory correspond to th... Read More

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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... Read More

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