Viscoelastic rheological property of different types of polymer solutions for enhanced oil recovery

The capability of hydrophobic association polymer(HAPAM) to displace oil is different from that of hydrolyzed polyacrylamide(HPAM) because they have different rheological properties.The viscoelasticity of five polymers was measured using Physica MCR301 rheometer and was compared.The five polymers include three HAPAMs with relative molecular mass of 1 248×104(TypeⅠ),750×104(TypeⅡ),and 571×104(Type Ⅲ) separately and two HPAMs with relative molecular mass of 1 200×104 and 3 800×104 respectively.The experiment results indicate that the viscoelasticity of HAPAM is better than that of HPAM.The storage modulus G' and the loss modulus G″ for HAPAM solutions are also larger than those for HPAM.Comparing the rheological curves of different HAPAM types,it is found that the viscosity of typeⅡ and type Ⅲ is almost same at different shear rates while the viscosity of type I is the lower than that of Types Ⅱ and Ⅲ.The storage modulus G' and the loss modulus G″ for three types of HAPAM were measured in low oscillation frequency range,and the results show that G' is greater than G″ for all three different types of HAPAM,but their loss modulus is almost same,and the G' is in the order of type Ⅱ>type Ⅲ>type I.In addition,the G' and G″ increase with aging time for all three HAPAM solutions were stayed at different days.The viscoelasticity of type Ⅰ reaches the highest value when aging time is 9 d at 45 ℃,but it is 7 d for type Ⅱ and type Ⅲ.The different viscoelasticity properties can be attributed to self-organization supermolecule networks which is formed by hydrophobic association of HAPAM molecular and molecular chain entanglement.

The Rheological and Extrusion Behaviour of Blends Based on Phenolphthalein Poly(ether-ether-sulfone)and Thermotropic Liquid Crystalline Polymer

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｔｈｅｌａｓｔｔｗｏｄｅｃａｄｅｓ，ｐａｒｔｉｃｕｌａｒａｔｅｎｔｉｏｎｈａｓｂｅｅｎｄｅｖｏｔｅｄｔｏｕｓｉｎｇｔｈｅｔｈｅｒｍｏｔｒｏｐｉｃｌｉｑｕｉｄｃｒｙｓｔａｌｉｎｅｐｏｌｙｍｅｒｓ（ＴＬＣＰ）ａｓａｒｅｉｎｆｏ...

Rheological Study of Polymers Used as Viscosity Index Improvers for Automotive Lubricant Oils

In this work, a rheological study of automotive lubricant oils, neutral light paraffinic (NLP) and neutral medium paraffinic (NMP), additivated with two commercial viscosity index improvers-VIIs, based on hydrogenated poly (isoprene-co-styrene), at different concentrations, was carried out. The study included the determination of the kinematic viscosity of the mixtures, the calculation of the viscosity indexes and their behavior when subjected to various rheometric experiments, including stress sweep, steady state flow, creep and recovery, and temperature ramp oscillatory tests. The obtained results showed the efficacy of the additives as viscosity index improvers, enabling a significant increase in the viscosity index of the pure oils at relatively low concentrations. The determination of the storage (G’) and of the loss (G”) moduli for the mixtures oil/VII additives showed a large predominance of the viscous effect over the elastic one. Except when under low shear stress, the mixtures showed a pseudoplastic behavior, with the flow curves being adjusted to fit the Ostwald-de-Waele model (Power Law), with negative flow behavior indexes.

Visualization of adaptive polymer flow and displacement in medium-permeable 3D core-on-a-chip

Polymer flooding has been witnessed an effective technology for enhancing oil recovery from medium-to low-permeability reservoirs;however, direct visualization of polymer solution flow in such reservoir condition is still lacking. In this work, a three-dimensional (3D) core-on-a-chip device with a permeability of around 200 mD was prepared and employed to visualize the pore-scale flow and displacement of a self-adaptive polymer (SAP, 8.7 × 106 g·mol−1)−whose microscopic association structure and macroscopic viscosity can reversibly change in response to shear action−versus partially hydrolyzed polyacrylamide (HPAM), by recording their flow curves, monitoring dynamic transportation process via particle imaging velocimetry, and building 3D structure of remaining oil. The results show that, in single-phase flow, all polymer solutions exhibit flow thinning and then thickening regions as flow rate increases, but the transition between two regimes occurs at a small Weissenberg number (10−3−10−1) in this medium-permeable condition. In contrast to HPAM-1 with close weight-average molecular weight (Mw), the adaptive character not only extends SAP's shear-govern region, allowing SAP to propagate piece by piece and achieve higher accessible pore volume, but it also enhances the elastic resistibility of polymer in the extension-dominated regime, increasing the microscopic displacement efficiency. These two effects result in 1.5–3 times more oil recovery factor for SAP than for HPAM-1. Regarding ultra-high-Mw HPAM-2 (25 × 106 g·mol−1), plugging and chain degradation do occur, thus producing lower oil recovery than SAP. This work provides a direct approach for in-situ assessment of polymer-based displacing system under a more authentic condition of practical reservoirs.

Rheological Behaviors of Polymers with Nanoparticles Tethered at Each End

The polymer with nanoparticles tethered at each end is a unique model for unraveling the effect of chain ends on the polymer dynamics. We investigated the rheological behavior of this kind of polymer by using nonequilibrium molecular dynamics simulation. The effect of polymer lengths and nanoparticle radii on the complex moduli and viscosity was examined. The dependence of complex moduli on the frequency becomes less pronounced as the polymer is short or the nanoparticle is large. The shear thinning behavior was revealed for these systems, and the scaling exponent of complex viscosity with respect to the frequency was found to change from-1/2 to-3/4 as the polymer shortens or the nanoparticle enlarges. The rheological behavior was further explained by analyzing the mean square distance of nanoparticles. The simulation results were compared with the existing experimental finding, showing an agreement. The work provides information for understanding the chain end effect on polymer rheology.

Rheological Properties of Hydrophobically Associating Polyacrylamide Solution

A temperature-resistant, salt-tolerant polyacrylamide, hydrophobically associating polymer （HAP）, was synthesized in the State Key Laboratory of Heavy Oil Processing. The rheological behavior of HAP solution was investigated by means of flow experiments in porous media and by using a HAAKE RS600 rheometer. The results of Nuclepore membrane filtration showed that filtration time increased sharply when the critical association concentration was reached. Shear rate had a greater impact on viscosity and shear stress with increasing HAP concentration. The HAP solution with a concentration of 100 mg/L （salinity 32,868 mg/L） exhibited negative thixotropy. However, at the same salinity the HAP solution showed thixotropy and its viscosity became greater when the polymer concentration increased to 1,500 mg/L. The flow experiments in cemented core samples indicated that the resistance factor and residual resistance factor of the HAP solution were 31.8 and 12 when polymer concentration and salinity were 1,500 mg/L, 32,868 mg/L at 85℃ respectively, which is favorable for flooding application. Such factors of partially hydrolyzed polyaerylamide 3530S were merely 3.14 and 1.71, so it could not be applied to polymer flooding in the oilfield with high temperature and high salinity.

Rheology of rock salt for salt tectonics modeling

Numerical modeling of salt tectonics is a rapidly evolving field; however, the constitutive equations to model long-term rock salt rheology in nature still remain controversial. Firstly, we built a database about the strain rate versus the differential stress through collecting the data from salt creep experiments at a range of temperatures（20–200 ℃） in laboratories. The aim is to collect data about salt deformation in nature, and the flow properties can be extracted from the data in laboratory experiments.Moreover, as an important preparation for salt tectonics modeling, a numerical model based on creep experiments of rock salt was developed in order to verify the specific model using the Abaqus package. Finally, under the condition of low differential stresses, the deformation mechanism would be extrapolated and discussed according to microstructure research. Since the studies of salt deformation in nature are the reliable extrapolation of laboratory data, we simplified the rock salt rheology to dislocation creep corresponding to power law creep（n = 5） with the appropriate material parameters in the salt tectonic modeling.

How Polymers Behave as Viscosity Index Improvers in Lubricating Oils

One of the requirements of engine lubricating oil is that it must have a low enough viscosity at low temperatures to assist in cold starting and a high enough viscosity at high temperatures to maintain its load-bearing characteristics. Viscosity Index (VI) is one approach used widely in the lubricating field to assess the variation of viscosity with temperature. The VI of both mineral and synthetic base oils can be improved by the addition of polymeric viscosity modifiers (VMs). VI improvement by VMs is widely attributed to the polymer coil size expanding with increasing temperature. However, there is very little physical data supporting this generally accepted mechanism. To address this issue, intrinsic viscosity measurements and Small-Angle Neutron Scattering (SANS) have been used to study the variation of polymer coil size with changing temperature and concentration in a selection of solvents. The results will show that coil size expansion with temperature is not necessary to achieve significant elevation of viscosity index.

Slipping Phenomenon in Polymeric Fluids Flow between Parallel Planes

At this article studies of nonlinear viscoelastic fluid with one internal tensor parameter flow between parallel planes under a constant pressure gradient, taking into account the slipping phenomenon on the boundary. Numerically depending found on the components of the stress tensor and the flow velocity of the pressure gradient and the distance to the wall, enabled us to explain the emergence of non-parabolic profile of the flow velocity of the polymeric melt.

Morphological, Rheological and Mechanical Properties of Pla-Typha Based Biocomposites

Due to the demand from society for the consumption of ecological polymeric materials, one of the polymers that have satisfied this request is the poly (lactic acid) (PLA). This polymer is derived from renewable resources, it is recyclable and biodegradable. It presents a good understanding between the promising properties and the cost. However, a route to increase the mechanical properties and reduce the cost of PLA is the elaboration of PLA based biocomposites by using fillers from natural waste. In this work, The effect of Typha content on the morphological, rheological, thermal and mechanical properties of PLA matrix was studied. Four formulations were produced with different mass concentrations. The results showed an increase in the viscoelastic properties, as a function of the Typha stem powder concentration. The DSC analysis showed an increase in the crystallinity rate of the various composites confirming the nucleating effect provided by the filler. TGA analysis indicated a decrease in the decomposition temperature of the composites. Mechanical tensile tests have shown a significant improvement in the mechanical properties mainly for the samples containing 45% (w/w) of Typha powder.

RHEOLOGICAL PROPERTIES OF LIQUID CRYSTALLINE COPOLY (ρ-HYDR0XYBENZ0ATE/BISPHENOL A TEREPHTHALATE)

Various aspects of the rheological behaviour of liquid crystalline copolyesters, i.e.,samples of copoly (p-hydroxybenzoate / bisphenol A terephthalate), were explored by usingInstron capillary rheometer. The experimental results indicated that the apparent viscositywas affected significantly by shear rate, melt temperature and p-hydroxybenzoate unit con-tent. The flow activation energies △E_η are in the range of 205.1 to 74.5 kJ/mol, dependingon the shear rate of 10-1000 s^(-1), at temperature 568-603K. These copolyesters exhibit ayield phenomenon in the shear flow, and the values of yield stress decrease with increasingtemperature. It is quite unusual that the extrudate of the copolyester shows the smallerswelling ratio even than unity at the lower temperature and lower shear rates.

The Mesoscopic Constitutive Equations for Polymeric Fluids and Some Examples of Viscometric Flows

Constitutive equations for melts and concentrated solutions of linear polymers are derived as consequences of dynamics of a separate macromolecule. The model is investigated for viscometric flows. It was shown that the model gives a good description of non-linear effects of simple shear polymer flows: viscosity anomalies, first and second normal stresses, non-steady shear stresses.

外掺料对C40透水混凝土性能的影响及机理分析

通过研究聚丙烯酸酯乳液掺量对透水混凝土抗压、抗折强度及透水系数的影响,确定其最佳掺量;采用SEM和XRD分析了透水混凝土的微观形貌和物相组成。研究了2种促凝剂对透水混凝土抗压强度、切片孔隙率的影响,并得出不同促凝剂的增强机理。研究了新型纳米材料(CNFs)对透水混凝土浆体流变性能及综合性能的影响。结果表明:聚合物乳液能在水泥浆体内部形成聚合物膜,对透水混凝土力学性能及透水功能均有改善;B组、C组促凝剂掺入后透水混凝土的7 d抗压强度明显提高,较未掺时最高分别提高了65.4%、77.0%;CNFs的掺入可使浆体呈剪切稀化现象,可用于调节浆体的触变性能,同时可显著提高透水混凝土的抗压强度,掺量0.15%时28 d抗压强度最高,较未掺时提高了56.8%。

井地过渡带对聚合物驱油剂性能影响研究

利用井地过渡带剪切模拟实验装置,以疏水缔合聚合物AP-P4为研究对象,研究不同吸水强度条件下,剪切后聚合物溶液的表观黏度、流变性、阻力和残余阻力系数、微观结构以及水动力学半径的变化情况。结果表明,经井地过渡带剪切后,随着吸水强度的增大,聚合物AP-P4溶液的黏度损失率高达61.4%,建立阻力系数和残余阻力系数的能力降低40.0%以上,但其建立残余阻力系数能力的降低幅度要比建立阻力系数能力的降低幅度小。聚合物溶液的储能模量和损耗模量降低,微观结构被破坏的越严重,水动力学半径越小。

POE溶液聚合反应器内混合与反应过程的CFD研究

聚烯烃弹性体(POE)具有优异的性能而应用广泛,其工业生产通常采用溶液聚合方法。POE反应介质流变行为复杂,受温度、剪切速率、聚合物浓度等诸多因素影响。同时,反应介质的流变行为是决定混合效果的重要因素,进而影响反应进程。由于反应、流变和流场的相互作用,POE溶液聚合反应器的设计和生产过程控制面临着挑战。基于实测的动力学和流变数据,针对POE溶液聚合反应器建立了一个耦合计算流体力学(CFD)模型,综合考虑了流动、混合效率、反应动力学和流变特性等方面的影响,探究了不同工艺条件(搅拌转速、停留时间、进料温度)对速度场、温度场、浓度场、流变特性等参数的影响规律,为优化实际工业过程提供参考。

偏高岭土对聚合物改性水泥浆体流变的影响

研究了偏高岭土掺量对不同水胶比的聚合物改性水泥浆体流动度、流变参数、触变性和粘弹性的影响.结果表明:掺入偏高岭土的复合浆体在新拌阶段的流变性能符合H-B模型,并且所有浆体均呈剪切稀化的流变特性.随着偏高岭土掺量的增大,浆体流动度、屈服应力和塑性黏度均增大.掺入20%偏高岭土后,水泥浆体的触变环面积由原来的1502 Pa·s^(-1)增加至6672.63 Pa·s^(-1),并且水胶比更低的浆体对应更大的触变面积.所有的复合浆体均存在明显的粘弹特性,并且当偏高岭土掺量越大时,浆体的临界点振幅和线性区的储能模量值均越大.

书评

对<Nonlinear Polymer Rheology:Macroscopic Phenomenology and Molecular Foundation>(高分子非线性流变学:宏观唯象学及其分子基础)流变学专著进行了全面深入的分析与评价.著者通过深入浅出的语言、生动形象的图解、严密深邃的辩证逻辑和极为简洁的数学表述,对高分子非线性流变学中的基本概念和模型(例如:屈服、有限内聚力和解缠结等),以及高分子非线性流变学中的典型现象(例如:应力过冲、非静态松弛、剪切带和应变硬化等),进行了系统地分析与探索.在我国推介此书,对年轻学者快速了解该领域的前沿工作有重要的指导作用,即使对从事本领域研究的学者,在启发创新思维和提高品判能力方面仍有相当的帮助.

Rheo-NMR: A versatile hyphenated technique for capturing molecular dynamics and structure under flow

The general development of Rheo-NMR during the last four decades as well as selective hyphenated apparatuses is presented.Based on different magnet types,the current review is divided into two categories,namely low-field and high-field NMR,while the timedomain NMR is normally applied in the former case and the frequency-domain NMR is adopted in the latter one.Depending on different rheometer cells,it can be further divided into tensile and shear mode Rheo-NMR.The combination of various rheometer cells and NMR facility guarantees our acquisition of molecular level structure and dynamics information under flow conditions,which is crucial for our understanding of the molecular origin of complex fluids.A personal perspective is also presented at last to highlight possible development in this direction.

聚合物表面活性剂在水泥基材料气泡调控中的应用现状

水泥基材料中的气泡调控一直以来都是学科难题,通过多因素提高水泥基材料中气泡的稳定性和可控性,对提高水泥基材料的流变性能和耐久性能具有十分重要的意义。在众多影响因素中,气泡调控型聚合物表面活性剂在水泥基材料气泡调控中起到十分关键的作用。文中首先对新拌混凝土中气泡的形成和破灭过程进行了简单介绍,综述了影响气泡稳定性的主要因素,如引气型外加剂、减水剂及纳米颗粒等对气泡稳定性的影响,同时介绍了近年来引气型外加剂的合成研究进展。最后,讨论了水泥基材料中气泡对混凝土性能的重要意义。