Flow Behavior Of Polymers Research Articles

Mechanical Properties and Flow Behavior of Polymers for Enhanced Oil Recovery

The mechanical properties and flow behavior in porous media of three different polymer systems including a hydrophobically modified acrylamide-based copolymer (HMSPAM), a partially hydrolyzed polyacrylamide (HPAM), and a polysaccharide (xanthan gum) were evaluated to establish their functional differentiation as mobility control agents in enhanced oil recovery (EOR). The rheological properties of the polymers were described by the power-law model to investigate their non-Newtonian behavior. The first normal stress difference (N1) and Weissenberg number (We) were also used to compare their elastic properties. The experimental results showed that, at comparable shear viscosity, HMSPAM exhibited significant elasticity compared to HPAM and xanthan gum. Shear resistance tests indicated that all of the polymers experienced an extra stress when converging into a capillary tube due to the “entrance effect.” Xanthan gum was the most mechanically stable polymer. Moreover, HMSPAM showed the superior reformability which was quantified by the regained viscosity with relaxation time. This could be explained by the rapid re-association of the hydrophobic interactions. Sandpack flood tests indicated that HMSPAM rendered extremely high mobility control ability during polymer flooding suggesting its potential in EOR. However, this polymer also experienced significant retention within the porous media (potential injectivity and plugging problems), which may be attributed to the formation of bulky associative polymer networks. In this work, UV spectrometry was employed to monitor the concentration of the produced polymer solutions and quantify the polymer retention within porous media. This analytical approach offers great reliability and simplicity. It was concluded that the use of a particular polymer system depends on the oil reservoir conditions and the target EOR application.

A novel method for the determination of steady-state torque of polymer melts by HAAKE MiniLab

HAAKE MiniLab is an apparatus specially designed for compounding polymer material and on-line testing of rheological properties. For the first time, it was used to establish a dynamic speed test method for the rapid determination of steady-state torque of polymer melts. The choices of sample feed quantity and screw rotation speed, as well as calibration for real torque, were carefully studied before torque measurements. The repeatability and reliability of torque data were also evaluated. Results showed that the torque could be calibrated by subtracting the torque without samples. Also, a feed quantity of ca. 6 g with a dynamic speed test range of 10–105 r/min was suitable for the determination of steady-state torque of polyolefin samples. The new method was quick, effective and reliable to correlate the steady-state torque with rotation speed. Therefore, MiniLab would be a very useful tool in exploring and characterizing polymer flow behavior through its torque measurements.

Mixing characteristics of different tracers in extrusion of polystyrene and polypropylene

To characterize the actual flow behavior of polymer, polystyrene (PS) and polypropylene (PP) macromolecular tracers were synthesized by copolymerization and graft routes. The two tracers were then used to obtain the residence time distribution (RTD) functions of PS and PP in a twin-screw extruder. The effect of temperature on RTD is discussed using different tracers. The mixing characteristics of different tracers in the extrusion of PS and PP were compared by measuring the overall and partial RTDs. The dependence of the overall and partial RTDs on the tracer types was investigated. The effects of mixing intensity, miscibility, and melting difference on the measured distribution were also discussed. POLYM. ENG. SCI., 54:310–316, 2014. © 2013 Society of Plastics Engineers

Influence of Mesh Discretization on the Prediction of Polymer Flow Behaviour in Microcavities

Microinjection moulding is one of the key technologies for the mass production of plastics microcomponents. Recently, significant effort has been made to test the limits of applicability of existent numerical codes for simulating the polymer flow at the microscale. However, the modelling precision in what concerns polymer flow in microimpressions depends on factors which may not be properly accounted for in the process simulation. In this study, a micropart with variable thickness was designed, and the moulding block fabricated and instrumented. Short shots and complete filling of the cavity were carried out and the flow front progress was subsequently evaluated. These data were also assessed numerically by 3D-finite element modelling. A flow simulation considering the polymer as incompressible was carried out to investigate how the mesh size and density affected the prediction of the flow field in the microimpression, using the same processing conditions of the experimental study. The reduction of the mesh size as well as the increase of the mesh density are consistent with better representativeness of the experimental flow front progress in the microimpression. Moreover, the weld line prediction also tends to be improved. This study suggests that the mesh adaption and domain discretization is important in numerical studies of the polymer flow at the microscale.

Technology Focus: EOR Performance and Modeling (January 2012)

Technology Focus In spite of continued investment and advances in exploiting alternative-energy sources, oil and natural gas will continue to be a significant portion of US and global energy portfolios for decades. Enhanced oil recovery (EOR) uses unconventional hydrocarbon-recovery methods that target the approximately two-thirds of the oil volume remaining in reservoirs after conventional-recovery methods have been exhausted. Though limited by high capital and operating costs, EOR techniques will have a substantial effect on the future supply of oil. In 2011, SPE hosted an EOR conference in Kuala Lumpur, and three workshops to address EOR technologies in Malaysia, Kuwait, and the Syrian Arab Republic. The Malaysia workshop focused on chemical-EOR methods, the Kuwait workshop addressed opportunities and for challenges of EOR methods in the Middle East, and the Syrian Arab Republic workshop discussed EOR in carbonate reservoirs. More than 300 EOR papers were published in SPE conferences, with many additional presentations in EOR workshops. These papers address important issues related to practical application of conventional EOR methods and the development of novel EOR technologies. The topics cover experience with, opportunities for, and challenges of EOR technologies; fundamental study of EOR mechanisms for different methods; feasibility study and improvement of an EOR method for a specific reservoir; EOR-screening criteria; reservoir surveillance, monitoring, and evaluation technologies; reservoir simulation and modeling; lessons learned from EOR pilot and field trials; and some novel EOR methods. Polymer flooding has been proved the most cost-effective chemical-EOR method in the laboratory and in the field. A recent focus on polymer flooding evaluated associative polymers because of their advantage over traditional hydrolyzed polyacrylamide (HPAM) polymers; thus, one paper about comparing the flow behavior of associative polymer and HPAM in porous media was selected for this feature. CO2 injection is a win/win strategy because it can enhance oil recovery and be used for CO2 storage in reservoirs to reduce greenhouse-gas levels in the atmosphere. However, CO2 EOR targets maximum oil recovery while CO2 sequestration targets maximum storage capacity without leakage. One paper featured here provides some guidance to balance the two technologies. Steamflooding has been applied successfully in heavy-oil reservoirs. However, one paper synopsized in this feature will describe successful steamflooding in a light-oil reservoir. Recommended additional reading at OnePetro: www.onepetro.org. SPE 142668 Enhanced Waterflood for Middle East Carbonate Cores—Impact of Injection-Water Composition. By Robin Gupta, ExxonMobil Upstream Research, et al. SPE 142105 A Simplified Model for Simulations of Alkaline/Surfactant/Polymer Floods. By Mojdeh Delshad, SPE, University of Texas at Austin, et al. SPE 144294 Large-Scale High-Viscous-Elastic-Fluid Flooding in the Field Achieves High Recoveries. By Wang Demin, SPE, Daqing Oil Company, et al. \ SPE 144599 A Combined Experimental and Simulation Workflow To Improve Predictability of In-Situ Combustion. By M. Bazargan, Stanford University, et al. SPE 147858 In-situ Combustion Using Sugar Dust, ‘Sweet Reservoirs’—A Smart and Better Alternative by Panchamlal, SPE, Maharashtra Institute of Technology, et al. SPE 147999 Lessons Learned From Nine Years of Immiscible-Gas-Injection Performance and Sector-Modeling Study of Two Pilots in a Heterogeneous Carbonate Reservoir by Lakshi Konwar, SPE, Zakum Development Company, et al.

1108 電場下における高分子液晶(poly-γ-benzyl L-glutamate/m-cresol溶液)の流動挙動(流体力学V)

1108 電場下における高分子液晶(poly-γ-benzyl L-glutamate/m-cresol溶液)の流動挙動(流体力学V)

A New Model of Polymers in Flow

Recent experimental evidence has shown that polymer chains compress in flow at semi-dilute concentrations. It has been assumed in all models of polymer flow behaviour that the chains extend in flow. A new model of polymers in flow in semi-dilute solution is presented where the chains compress. The chains are modeled as simple Hookean dumbbells exposed to compressive hydrodynamic forces. Equating the hydrodynamic and elastic forces predicts chain compression with shear rate. The model predicts both the power law behaviour observed for polymer shear thinning and the measured decrease in radius with shear rate with reasonable accuracy.

Rheological (visco-elastic behaviour) analysis of cyclic olefin copolymers with application to hot embossing for microfabrication

Transparent, amorphous cyclic olefin copolymers (COCs) have been frequently used for the fabrication of microfluidic devices using a hot embossing technique for numerous applications. In hot embossing, the polymer is deformed near its glass transition temperature (Tg), i.e. between Tg and Tg + 60 °C where the viscoelastic properties of the material are dominant. The proper characterization of the viscoelastic properties is of interest as this can lead to a better understanding of polymer flow behaviour during microfabrication. Furthermore, the ability to model its rheological behaviour will enable the prediction of the optimal hot embossing processing parameters. We performed small amplitude oscillatory shear experiments on four grades of COCs, TOPAS-8007, TOPAS-5013, TOPAS-6015 and TOPAS-6017, in order to characterize their flow behaviour. The experiments were conducted within the frequency range from 0.01 to 500 Hz at between Tg + 20 and Tg + 60 °C. The flow properties could be represented using a generalized Maxwell viscoelastic constitutive model with Williams–Landel–Ferry-type temperature dependence. Good fit of the experimental data was obtained over a wide range of temperatures. The model could be coupled with ABAQUS finite element software to predict the optimal conditions for fabricating a capillary electrophoresis micro-chip on a TOPAS-5013 substrate by hot embossing.

Determination of suspension viscosity from the flow velocity profile measured by Doppler Optical Coherence Tomography

In this paper we present, for the first time to our knowledge, the experimental results for determining suspension viscosity in a capillary type viscometer from flow velocity profiles measured by Doppler Optical Coherence Tomography. The suspension of 0.3?m polystyrene microspheres in a glycerol-water solution was used as a model fluid. The viscosity of the suspension was controlled by glycerol concentration. The shear rate and the shear stress at the capillary wall were measured at six flow rates. The corresponding viscosities were calculated. The comparison of the measured shear rates with the values calculated according to the flow rate of the syringe precision pump was performed. Additionally, the viscosities of the studied suspensions were measured by a rotational viscometer. Full Text: PDFReferences K.A. Hayes, M.R. buckley, I. Cohen, L.A. Archer, "High Resolution Shear Profile Measurements in Entangled Polymers", Phys. Rev. Lett. 101, 218301 (2008)[CrossRef] N. Willenbacher, H. Hanciogullari, H.G. Wagner, "High shear rheology of paper coating colors ? more than just viscosity", Chem. Eng. Technol. 20, 557 (1997)[CrossRef] M. Iotti, O.W. Gregersen, S. Moe, M. Lenes, "Rheological Studies of Microfibrillar Cellulose Water Dispersions", J. Polym. Environ. 19, 137 (2011)[CrossRef] M.T. Roberts, A. Mohraz, K.T. Christensen, J.A. Lewis, "Direct Flow Visualization of Colloidal Gels in Microfluidic Channels", Langmuir 23, 8726 (2007)[CrossRef] M. Schmidt, E. Wassner, H. Münstedt, "Setup and Test of a Laser Doppler Velocimeter for Investigations of Flow Behaviour of Polymer Melts", Mech. Time-Depend. Mater. 3, 371, (1999)[CrossRef] S. Schuberth, H. Münstedt, "Simultaneous measurements of velocity and stress distributions in polyisobutylenes using laser-Doppler velocimetry and flow induced birefringence", Rheol. Acta 47, 111 (2008)[CrossRef] Th. Wunderlich, P.O. Brunn, "A wall layer correction for ultrasound measurement in tube flow: comparison between theory and experiment", Flow Meas. Instrum. 11, 63 (2000)[CrossRef] J. Wiklund, I. Shahram, M. Stading, "Methodology for in-line rheology by ultrasound Doppler velocity profiling and pressure difference techniques", Chem. Eng. Sci. 62, 4277 (2007)[CrossRef] S. Yazdanfar, M.D. Kulkarni, J.A. Izatt, "High resolution imaging of in vivo cardiac dynamics using color Doppler optical coherence tomography", Opt. Express 1(13), 424 (1997)[CrossRef] Y. Zhao et al., "Phase-resolved optical coherence tomography and optical Doppler tomography for imaging blood flow in human skin with fast scanning speed and high velocity sensitivity", Opt. Lett. 25(2), 114 (2000)[CrossRef] J. Moger, S.J. Matcher C.P. Winlove, A. Shore, "Measuring red blood cell flow dynamics in a glass capillary using Doppler optical coherence tomography and Doppler amplitude optical coherence tomography", J. Biomed. Opt. 9(5), 982 (2004)[CrossRef] S. Tamborski et al., "Simultaneous analysis of flow velocity and spectroscopic properties of scattering media with the use of joint Spectral and Time domain OCT", Phot. Lett. Poland 1(2), 49 (2009) B. Povazay et al., "Submicrometer axial resolution optical coherence tomography", Opt. Lett. 27(20), 1800 (2002)[CrossRef] M. Harvey, T.A. Waigh, "Optical coherence tomography velocimetry in controlled shear flow", Phys. Rev. E 83, 031502 (2011)[CrossRef] J. Lauri, M. Wang, M. Kinnunen, R. Myllylä, "Measurement of microfluidic flow velocity profile with two Doppler optical coherence tomography systems", Proc. SPIE 6863, 68630F (2008)[CrossRef]

Numerical Simulation of Polymer Flows in Coat-Hanger Die Using Wagner Constitutive Model

An understanding of flow behavior of polymer melts through a slit die is extremely important for optimizing die design. In this paper numerical simulations have been undertaken for the flow of linear low-density polyethylene through Coat-hanger sheet dies. A new finite element method is proposed to simulate the flow in slit channel using Wagner constitutive model. This is one kind of finite element semi-analytical method by which the velocity distributions in thickness direction is approach by Fourier series. Numerical results of volumetric flow and pressure in coat-hanger dies are given to compare to the three-dimensional simulation using the finite element method. It appears that numerical solutions are as accurate as the complete 3D calculations and the computing time can be saved.

Flow behavior in a corotating twin‐screw extruder of pure polymers and blends: Characterization by fluorescence monitoring technique

AbstractThe objective of this work was to investigate the flow behavior of pure polymers and blends, especially miscible polymer/polymer systems, in a corotating twin‐screw extruder (TSE) using an online fluorescence monitoring device. An immiscible blend was also studied for the sake of comparison. The fluorescence signal was obtained by using synthesized fluorescence tracers added to the melt at very low concentrations. These tracers consisted of two styrene‐maleic anhydride copolymers (SMA) labeled with anthracene. The investigated blends were SMA8 (8 wt % of MA in SMA)/polystyrene (PS), SMA14 (14 wt % of MA in SMA)/styrene acrylonitrile copolymer (SAN), and poly(methyl methacrylate) (PMMA)/ethyl acrylate‐methyl methacrylate copolymer (PMMAEA). The residence time distribution (RTD), the mean residence time (t), the dimensionless variance (σθ2), the Peclet number (Pe) and the fluorescence peak intensity distribution of pure polymers and binary polymer systems were investigated and interpreted in terms of polymers rheological properties. It was observed that polymers presenting higher viscosity or higher pressure showed longer residence time. A difference in behavior was also observed for the RTD of miscible and immiscible blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Experimental and analytical study on filling of nano structures in micro injection molding

Nano technology is attracting more attention and has increasing applications in the recent years. Among the products with nano technology, many of them are made of polymer plastics. Micro injection molding is one of the critical processes for polymer plastics. In micro injection molding, the ability for the polymer melt to flow into the micro/nano structures is a crucial factor for successful molding. The flow behavior of polymer in nano structures needs to be explored further to facilitate the molding process. In this study, we investigated the effects of the processing parameters on the filling of nano structures analytically and experimentally. Firstly, mold inserts with nano channels were constructed by LIGA-Like process. Secondly, an analytical model was developed to model the filling of polymer melt in the nano channels. Molding experiments were performed to verify the analytical filling model. With this verified model, a theoretical penetration distance can be obtained, and the suitable processing parameters can be estimated for different product geometries.

Continuous roll-to-flat thermal imprinting process for large-area micro-pattern replication on polymer substrate

Conventional imprinting process in flat-pressing mode meets with the problem of limited efficiency as a discontinuous batch-wise process in many new applications that demand micro-/nano pattern replication over large area with low cost and high throughout in mass production manufacturing. To overcome such problem, alternative imprinting process in a continuous roller-pressing mode has been gaining more attention since it has many advantages. However, few studies have been reported on the investigation of filling mechanism in roller-pressing type imprinting process. In order to have a better understanding of polymer flow behavior in roller-pressing type imprinting process, it is necessary to establish a criterion of evaluation for roller-pressing type imprinting process. In this paper, an analytical model for the cavity-filling of polymer flow in roll-to-flat (R2F) imprinting process is derived based on Hertz contact pressure distribution and Navier–Stokes equation. The feasibility of the model is evaluated using a lab-scaled prototype of a R2F micro thermal imprint system for micro-pattern replication over large area on polymer substrate. Series of tests are conducted to investigate the effects of process control parameters on the replication ratio. In results, there is good agreement between the model prediction and experiments when pattern replication is examined according to the change of control parameters such as rolling speed and loading pressure.

Design basis and hydrodynamic performance analysis of single‐screw extruders. I – polymer flow behaviour

PurposeThe purpose of this paper is to investigate the hydrodynamic performance of a single‐screw extruder with special reference to metering region.Design/methodology/approachThe hydrodynamic analysis of a single screw extruder is carried out by dimensional and non‐dimensional parameters defining the polymer flow behaviour. The flow types formed in the extruder channel are defined and the relationship between the flow with the extruder geometry is examined.FindingsThe theoretical model developed is capable of estimating the hydrodynamic behaviour of extruder metering region. With the model developed, extruder geometry and polymer flow rate under different operating conditions can be predicted.Originality/valueThis paper offers a quick and easy opportunity to examine the hydrodynamic behaviour of extruder metering region. With the theoretical model developed, the behaviour of the flow in extruder can be modelled and estimated.

Steady state measurements in stress plateau region of entangled polymer solutions: Controlled-rate and controlled-stress modes

Despite decades of efforts, reliable measurements of nonlinear flow behavior of well-entangled polymers in continuous shear have been challenging to obtain. The present work attempts to accomplish three important tasks: (A) overcome this challenge by adopting a strategy of decoupling rheological measurements from the outer meniscus region in a cone-partitioned plate (C/PP) setup; (B) determine whether well-entangled solutions indeed undergo a flow transformation under creep that can be taken to phenomenologically define an entanglement-disentanglement transition (EDT); (C) provide the velocity profiles of such solutions undergoing either controlled-stress or controlled-rate shear by carrying out in situ particle-tracking velocimetric (PTV) measurements. Upon removing any influence of edge fracture and sample loss, we are able to reach steady state during continual shear and elucidate more reliably the nonlinear flow behavior of well entangled polymer solutions with little ambiguity. Three well-entangled s...

Analysis of the Isothermal Compression in Nanoimprint Lithography Assuming a Power-Law Fluid

Abstract One of the choices for defining a nano pattern in micro fabrication is to use the nanoimprint lithography. This method is also known as a hot embossing lithography due to its inherited process technique from the compression process. It is important to determine the appropriate conditions of pressure, temperature, and time in the nanoimprint lithography process. To determine the right conditions for nanoimprint lithography, one has to understand the polymer flow behavior during the imprinting process. In this study, a simplified analytical model was developed based on a power-law fluid to predict the polymer flow during the imprinting process. Under a constant imprint force, the imprint depth on a polymer film can be predicted using this model. Experimental tests were also conducted to verify the results. It was demonstrated that the model can provide reasonable results on the imprint depth.

Effect of hot embossing process parameters on polymer flow and microchannel accuracy produced without vacuum

To investigate the basic mechanism of hot embossing, a series of experiments were conducted by using male die with micro-features. With online and outline methods, the polymer flow behavior during microembossing was observed. A hot embossing method without vacuum to achieve high replication accuracy was presented. Orthogonal experiment was used to establish the relationship between hot embossing conditions and replication accuracy. The results of the present work implied that during hot embossing cycle, the increasing temperature and pressure stage will determine the replication accuracy of microchannel in depth, and the replication accuracy of width and shape was determined by maintaining temperature and pressure stage. The replication accuracy depends strongly on the processing conditions. By using new hot embossing method, the replication accuracy has reached about 99%.

Three-dimensional entrance flow of a low-density polyethylene (LDPE) and a linear low-density polyethylene (LLDPE) into a slit die

A common method to characterize polymer melts is the slit rheometry. With this technique the shear viscosity can be measured up to high shear rates. For the evaluation it is assumed that within the capillary a pure shear flow exists. This paper investigates the flow patterns within such a “black box” using laser-Doppler velocimetry (LDV) which allows the measurement of the velocity fields of molten polymer melts with high spatial and temporal resolution. Therefore, this method was applied to get a deeper insight into the flow behaviour of polymer melts into and in a slit die. The materials investigated are two polyethylenes, a linear low-density polyethylene (LLDPE) and a low-density polyethylene (LDPE). Differences between these two samples are that the LLDPE is less shear thinning than the LDPE and that the elasticity is higher for the LDPE. Furthermore, the LDPE is strain hardening, the LLDPE is not. For the LDPE a pronounced secondary flow in the corners of the flow channel was found which did not occur for the LLDPE. These vortices change their shape if characterized along the neutral direction giving rise to a distinct three-dimensionality of the flow field. In addition, it was observed that within the vortices a helical flow exists which is directed to the walls of the reservoir. Special attention is paid to the velocity distribution along the symmetry axis of the channel. It was found that the LDPE shows a velocity maximum directly behind the die entrance, which does not appear for the LLDPE under the same flow conditions. It could be shown that this velocity overshoot is due to the three-dimensionality of the flow field which was observed for the strain-hardening LDPE, but not for the LLDPE. The three-dimensionality of the flow of the LDPE is marked by a velocity component in the neutral direction ( z-direction), which does not appear for the LLDPE. This additional component effects a higher volume flow along the centreline in the die entrance plane. The time dependence of the rearrangement of the flow field within the slit can be related to the relaxation times of the material.

Intercomparison of slip flow velocity measurements of filled polymers by capillary extrusion rheometry

Slip flow can complicate both the measurement of the shear flow behaviour of polymers and the modelling of moulding processes. However, the understanding of the reliability of methods for measuring slip flow behaviour is limited. The results of an intercomparison on the measurement of slip flow behaviour by capillary extrusion rheometry of two polymer melts—a filled high-density polyethylene and a filled ethylene–vinyl acetate copolymer—are reported. Slip velocities were calculated, following the Mooney method, from the dependence of the shear stress–shear rate behaviour on the extrusion die diameter. Both compounds exhibited wall slip: in one case the slip velocity accounted for ≈ 80 % of the total flow rate. Slip velocity results were typically within ≈ ± 20 % of the average values for the materials, although scatter up to ≈ ± 40 % was obtained for one material at high shear stresses. An analysis of slip velocity measurements indicated that uncertainties of 40–50% are typical (95% confidence level) although significantly higher uncertainties could result if testing conditions (primarily die diameters) are not optimised.

Characterizing nanoimprint profile shape and polymer flow behavior using visible light angular scatterometry

The profile shape and the flow behavior of polymer nanoscale gratings made by a thermal nanoimprint process are precisely examined using visible light angular scatterometry. Nanoimprinted poly(methyl methacrylate) (PMMA) lines with 60–800nm width, 100–200nm height, and varied residual thicknesses of 70–400nm have been investigated using this optical approach, and insightful observations are made regarding residual stress buildup during thermal nanoimprint. In addition, a nonlinear profile model has been developed for scatterometry to monitor the “melting” behavior of PMMA gratings under annealing around its glass transition temperature. The polymer nanostructures were found to relax primarily at high stress regions.