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1
Harper, B. D. "Influence of Polymer Viscoelasticity on a Bending Bilayer". Journal of Electronic Packaging 116, nr 3 (1.09.1994): 191–97. http://dx.doi.org/10.1115/1.2905685.
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The bending bilayer technique is commonly employed to provide an empirical assessment of the often significant thermal stresses that develop in thin polymer films used in microelectronic packaging. Polymers are known to exhibit time-dependent (viscoelastic) behavior that is greatly accelerated at elevated temperatures. The solution for a bilayer beam with a linear viscoelastic, thermorheologically simple film bonded to a linear elastic substrate is developed. A wide variety of assumed viscoelastic material properties are considered along with properties for several specific electronic polymers in order to illustrate the general effects of polymer viscoelasticity upon the thermal stress in a polymer film. Practical methods for deducing the relative significance of polymer viscoelasticity from empirical bending bilayer results are emphasized. Comparisons with experimental data for two polymides and one epoxy molding compound are also provided.
2
Clarke, A., A. M. Howe, J. Mitchell, J. Staniland i L. A. Hawkes. "How Viscoelastic-Polymer Flooding Enhances Displacement Efficiency". SPE Journal 21, nr 03 (15.06.2016): 0675–87. http://dx.doi.org/10.2118/174654-pa.
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Summary Increasing flooding-solution viscosity with polymers provides a favorable mobility ratio compared with brine flooding and hence improves volumetric sweep efficiency. Flooding with a polymer solution exhibiting elastic properties has been reported to increase displacement efficiency, resulting in a sustained doubling of the recovery enhancement compared with the use of conventional viscous-polymer flooding (Wang et al. 2011). Flooding with viscoelastic-polymer solutions is claimed also to increase recovery more than expected from changes in capillary number alone (Wang et al. 2010). This increase in displacement efficiency by viscoelastic polymers is reported to occur because of changes in the steady-state-flow profile and enhancements in oil stripping and thread formation. However, within the industry there are doubts that a genuine effect is observed, or that improvements in displacement efficiency occur with field-applicable flow regimes (Vermolen et al. 2014). In this study, we demonstrate that flooding with viscoelastic-polymer solutions can indeed increase recovery more than expected from changes in capillary number. We show a mechanism of fluctuations in flow at low Reynolds number by which viscoelastic-polymer solutions provide improvements in displacement efficiency. The mechanism, known as elastic turbulence, is an effect previously unrecognized in this context. We demonstrate that the effect may be obtained at field-relevant flow rates. Furthermore, this underlying mechanism explains both the enhanced capillary-desaturation curves and the observation of apparent flow thickening (Delshad et al. 2008; Seright et al. 2011) for these viscoelastic solutions in porous media. The work contrasts experiments on flow and recovery by use of viscous and viscoelastic-polymer solutions. The circumstances under which viscoelasticity is beneficial are demonstrated. The findings are applicable to the design of formulations for enhanced oil recovery (EOR) by polymer flooding. A combination of coreflooding, micromodel flow, and rheometric studies is presented. The results include single-phase and multiphase floods in sandstone cores. Polymer solutions are viscoelastic [partially hydrolyzed polyacrylamide (HPAM)] or viscous (xanthan). The effects of molecular weight, flow rate, and concentration of the HPAMs are described. The data lead us to suggest a mechanism that may be used to explain the observations of improved displacement efficiency and why the improvement is not seen for all viscoelastic-polymer floods.
3
Negmatov, Soyibjon, T. Ulmasov, Farxod Navruzov i S. Jovliyev. "Vibration damping composition polymer materials and coatings for engineering purpose". E3S Web of Conferences 264 (2021): 05034. http://dx.doi.org/10.1051/e3sconf/202126405034.
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To develop and create effective vibration-damping composite polymer materials (VDСPM) with high viscoelastic and strength properties, the choice of research objects to increase durability reduces vibration of parts and structures of machines consequently, the noise level in industrial premises is stated and substantiated. A method is described for studying the viscoelastic properties, adhesive strength, microhardness, impact strength of polymer coatings, and compositions based on them, filled with organomineral ingredients. The results of studies of the viscoelastic and physicomechanical properties of polymer composite materials based on epoxy polymers and an organomineral filler - rubber powder are presented. Based on complex analyzes and the obtained results of the study of the physicomechanical and viscoelastic properties of materials, several effective compositions of vibration-damping polymer materials using rubber powder have been developed.
4
Ashrafi, Hosein, M. R. Bahadori i M. Shariyat. "Modeling of Viscoelastic Solid Polymers Using a Boundary Element Formulation with Considering a Body Load". Advanced Materials Research 463-464 (luty 2012): 499–504. http://dx.doi.org/10.4028/www.scientific.net/amr.463-464.499.
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In this work, a boundary element formulation for 2D linear viscoelastic solid polymers subjected to body force of gravity has been presented. Structural analysis of solid polymers is one of the most important subjects in advanced engineering structures. From basic assumptions of the viscoelastic constitutive equations and the weighted residual techniques, a simple but effective boundary element formulation is implemented for standard linear solid (SLS) model. The SLS model provides an approximate representation of observed behavior of a real advanced polymer in its viscoelastic range. This approach avoids the use of relaxation functions and mathematical transformations, and it is able to solve quasistatic viscoelastic problems with any load time-dependence and boundary conditions. Problem of pressurization of thick-walled viscoelastic tanks made of PMMA polymer, which subjected to a body force, is completely analyzed.
5
Tahir, Muhammad, Rafael E. Hincapie i Leonhard Ganzer. "An Elongational and Shear Evaluation of Polymer Viscoelasticity during Flow in Porous Media". Applied Sciences 10, nr 12 (17.06.2020): 4152. http://dx.doi.org/10.3390/app10124152.
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This paper uses a combination of approaches to evaluate the viscoelastic phenomenon in high-molecular-weight polymers (24–28 M Daltons) used for enhanced oil recovery (EOR) applications. Rheological data were cross-analyzed with single- and two-phase polymer flooding experiments in outcrop cores and micromodels, respectively. First, the impact of semi-harsh conditions (salinity, hardness, and temperature) was evaluated. Second, the impact of polymer degradation (sand face flow), focusing on the viscoelastic properties, was investigated. Finally, polymer viscoelastic properties were characterized, proposing a threefold rheological approach of rotational, oscillatory, and elongational behavior. Data from the rheological approaches were cross-analyzed with core flooding experiments and performed at a room temperature of 22 °C and at a higher temperature of 55 °C. The change in polymer viscoelastic properties were analyzed by investigating the effluents from core flooding experiments. Oil recovery experiments in micromodel helped our understanding of whether salinity or hardness has a dominating impact on in situ viscoelastic polymer response. These approaches were used to study the impact of mechanical degradation on polymer viscoelasticity. The brines showed notable loss in polymer viscoelastic properties, specifically with the hard brine and at higher temperature. However, the same polymer solution diluted in deionized water exhibited stronger viscoelastic properties. Multiple flow-behaviors, such as Newtonian, shear thinning, and thickening dominated flow, were confirmed through pressure drop analysis against interstitial velocity as already reported by other peer researchers. Turbulence-dominated excessive pressure drop in porous media was calculated by comparing core flood pressure drop data against pressure data in extensional viscometer–rheometer on a chip (eVROC®). In addition, a significant reduction in elastic-dominated flow was confirmed through the mechanical degradation that happened during core flood experiments, using various approaches. Finally, reservoir harsh conditions (high temperature, hardness, and salinity) resulted in a significant reduction in polymer viscoelastic behavior for all approaches.
6
Brostow, Witold, Hanna Fałtynowicz, Osman Gencel, Andrei Grigoriev, Haley E. Hagg Lobland i Danny Zhang. "Mechanical and Tribological Properties of Polymers and Polymer-Based Composites". Chemistry & Chemical Technology 14, nr 4 (15.12.2020): 514–20. http://dx.doi.org/10.23939/chcht14.04.514.
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A definition of rigidity of polymers and polymer-based composites (PBCs) by an equation is formulated. We also discuss tribological properties of polymers and PBCs including frictions (static, sliding and rolling) and wear. We discuss connections between viscoelastic recovery in scratch resistance testing with brittleness B, as well as Charpy and Izod impact strengths relations with B. Flexibility Y is related to a dynamic friction. A thermophysical property, namely linear thermal expansivity, is also related to the brittleness B. A discussion of equipment needed to measure a variety of properties is included.
7
Kubo, Takao, Shiro Ota, Masatoshi Oda, Kenichi Hashishita i Yasuhiro Kakinuma. "Evaluation of Polished Surface for Viscoelastic Polymer". Advanced Materials Research 126-128 (sierpień 2010): 493–98. http://dx.doi.org/10.4028/www.scientific.net/amr.126-128.493.
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Viscoelastic polymers are used as one of coating materials for protecting the products from scratches. Presently, the repair of the coating surface for removing dust or extraneous matters has been performed through several polishing processes. However, it becomes increasingly difficult to polish its surface by only applying good skill and experience of skilled worker because a leading-edge viscoelastic polymer for coating is further scratch-resistant. Thus, based on quantitative evaluation of relation between polishing process and finished surface, it is necessary to make the polishing process appropriate for the leading-edge viscoelastic polymers. In this study, we attempt to establish the evaluation method of the polished surface and clarify the surface condition with invisible scratches.
8
Azad, Madhar S., i Japan J. Trivedi. "Extensional Effects during Viscoelastic Polymer Flooding: Understanding Unresolved Challenges". SPE Journal 25, nr 04 (27.04.2020): 1827–41. http://dx.doi.org/10.2118/201112-pa.
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Summary Several studies have tried to relate polymers’ enhanced oil recovery (EOR) potential to their viscoelastic characteristics such as onset, rheo thickening, extensional viscosity, and Deborah number (De). Contradictions prevail when it comes to reduction in residual oil saturation (Sor) during polymer flooding and the role of extensional properties. De calculated using the oscillatory relaxation time fails to explain the different pressure profiles exhibited by the viscous and viscoelastic polymers. Extensional viscosity has been ignored in many studies as the reason for additional Sor reduction based on the core-scale apparent viscosity and core-scale capillary number (Nc). In recent studies, a significant oil mobilization was shown by the viscoelastic polymers even before the critical Nc, which indicates that the capillary theory breaks out under specific conditions during polymer flooding. Moreover, the additional residual oil recovery caused by the high-salinity polymer solutions cannot be explained by the oscillatory De. In this paper, we compile and examine many such unresolved challenges from various literature with rheological and petrophysical insights. The uniaxial bulk extensional rheology is performed on the relevant polymers using a capillary breakup extensional rheometer to measure the extensional relaxation time, maximum extensional viscosity at the critical De, and strain hardening index. A detailed analysis signifies the role of extensional rheology on the viscoelastic onset, rheo thickening, and Sor reduction even under varying salinity conditions. The results also highlight the advantages of extensional rheology over oscillatory rheology and validate the capillary theory using modified capillary number.
9
Li, Can-Qi, Horst Henning Winter, Yuan-Qi Fan, Geng-Xin Xu i Xue-Feng Yuan. "Time–Concentration Superposition for Linear Viscoelasticity of Polymer Solutions". Polymers 15, nr 7 (6.04.2023): 1807. http://dx.doi.org/10.3390/polym15071807.
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The concentration dependence of linear viscoelastic properties of polymer solutions is a well-studied topic in polymer physics. Dynamic scaling theories allow qualitative predictions of polymer solution rheology, but quantitative predictions are still limited to model polymers. Meanwhile, the scaling properties of non-model polymer solutions must be determined experimentally. In present paper, the time–concentration superposition (TCS) of experimental data is shown to be a robust procedure for studying the concentration scaling properties of binary and ternary polymer solutions. TCS can not only identify whether power law scaling may exist or not, and over which concentration range, but also unambiguously estimate the concentration scaling exponents of linear viscoelastic properties for a range of non-model polymer solutions.
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Kim, Taehyung, Kyoungsei Choi i Won Ho Jo. "A Stochastic Dynamics Simulation of Viscoelastic Properties of Polymer Blends: Intermolecular Interaction Effects". Journal of Polymer Engineering 18, nr 1-2 (1.03.1998): 1–16. http://dx.doi.org/10.1515/polyeng-1998-1-203.
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Abstract Stochastic dynamics simulations were performed to investigate the viscoelastic properties of polymer blends. In this simulation, three model systems with different intermolecular interactions are used to examine the effect of intermolecular interaction on the viscoelastic properties of polymer blends. Structural information such as the radius of gyration, orientation factor and radial distribution function of polymers is calculated from computer simulations as a function of shear rate and then is related to simulated viscoelastic properties of polymer blends. The effect of intermolecular interaction on the viscosity becomes different depending upon the magnitude of shear rate. At lower shear rate regions, more attractive intermolecular interaction results in lower viscosity due to chain stretching. But, at higher shear rate regions, more attractive interaction results in higher viscosity due to more dense packing of chains induced by the intermolecular attraction.
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Anderson, Patrick D., Joseph Dooley i Han E. H. Meijer. "Viscoelastic Effects in Multilayer Polymer Extrusion". Applied Rheology 16, nr 4 (1.08.2006): 198–205. http://dx.doi.org/10.1515/arh-2006-0014.
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Abstract The effect of viscoelasticity on multilayer polymer extrusion is discussed. In these coextrusion processes predetermined patterns are created with a remarkable breadth of complexity even in geometrically simple dies via elastic rearrangements caused by the second-normal stress differences. A computational method is offered, based on the mapping method, which quantitatively describes the flow-induced patterns. Besides that the results are esthetically beautiful, they are also relevant for practice, since process and die design optimization is now possible. Not only to minimize interface distortion, but potentially also to deliberately create new processes and products based on this flow-induced patterning of polymers.
12
Shinohara, Akira, Chengjun Pan, Zhenfeng Guo, Liyang Zhou, Zhonghua Liu, Lei Du, Zhichao Yan, Florian J. Stadler, Lei Wang i Takashi Nakanishi. "Viscoelastic Conjugated Polymer Fluids". Angewandte Chemie International Edition 58, nr 28 (8.07.2019): 9581–85. http://dx.doi.org/10.1002/anie.201903148.
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Goswami, Shubham, i Arman Hemmati. "Response of Viscoelastic Turbulent Pipeflow Past Square Bar Roughness: The Effect on Mean Flow". Computation 9, nr 8 (30.07.2021): 85. http://dx.doi.org/10.3390/computation9080085.
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The influence of viscoelastic polymer additives on response and recovery of turbulent pipeflow over square bar roughness elements was examined using Direct Numerical Simulations at a Reynolds number of 5×103. Two different bar heights for the square bar roughness elements were examined, h/D=0.05 and 0.1. A Finitely Extensible Non-linear Elastic-Peterlin (FENE-P) rheological model was employed for modeling viscoelastic fluid features. The rheological parameters for the simulation corresponded to a high concentration polymer of 160 ppm. Recirculation regions formed behind the bar elements by the viscoelastic fluid were shorter than those associated with Newtonian fluid, which was attributed to mixed effects of viscous and elastic forces due to the added polymers. The recovery of the mean viscoelastic flow was faster. The pressure losses on the surface of the roughness were larger compared to the Newtonian fluid, and the overall contribution to local drag was reduced due to viscoelastic effects.
14
Spathis, G., i E. Kontou. "A viscoelastic model for predicting viscoelastic functions of polymer and polymer nanocomposites". International Journal of Solids and Structures 141-142 (czerwiec 2018): 102–9. http://dx.doi.org/10.1016/j.ijsolstr.2018.02.015.
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Younes, Basel. "Simple Rheological Analysis Method of Spinnable-Polymer Flow Properties Using MFI Tester". Indian Journal of Materials Science 2015 (5.07.2015): 1–8. http://dx.doi.org/10.1155/2015/790107.
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Rheological characterization of polymers explains the flow behaviour and viscoelastic properties and tests fibre-forming ability. The current method investigates the viscoelastic properties and morphology of polymers and finds the rheological data and the right polymer viscosity, which is determining the best processing temperature. The right processing temperature saves the power, the material, and the time needed for production. After calculating polymers viscosity by using MFI tester, the method investigates rheological properties and surface shape at different temperatures and loads. The method could apply to other polymers to find the viscosity-temperature change and to set the best processing temperature.
16
Qi, Pengpeng, Daniel H. Ehrenfried, Heesong Koh i Matthew T. Balhoff. "Reduction of Residual Oil Saturation in Sandstone Cores by Use of Viscoelastic Polymers". SPE Journal 22, nr 02 (25.10.2016): 447–58. http://dx.doi.org/10.2118/179689-pa.
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Summary Water-based polymers are often used to improve oil recovery by increasing sweep efficiency. However, recent laboratory and field work have suggested these polymers, which are often viscoelastic, may also reduce residual oil saturation (ROS). The objective of this work is to investigate the effect of viscoelastic polymers on ROS in Bentheimer sandstones and identify conditions and mechanisms for the improved recovery. Bentheimer sandstones were saturated with a heavy oil (120 cp) and then waterflooded to ROS with brine followed by an inelastic Newtonian fluid (diluted glycerin). These floods were followed by injection of a viscoelastic polymer, hydrolyzed polyacrylamide (HPAM). Significant reduction in residual oil was observed for all corefloods performed at constant pressure drop when the polymer had significant elasticity (determined by the dimensionless Deborah number, NDe). An average residual-oil reduction of 5% original oil in place (OOIP) was found during HPAM polymer floods for NDe of 0.6 to 25. HPAM floods with very-low elasticity (NDe < 0.6) did not result in observable reduction in ROS; however, another 10% OOIP residual oil was reduced when the flow rate was increased (NDe > 25). All experiments at constant pressure drop indicate that polymer viscoelasticity reduces the ROS. Results from computed-tomography (CT) scans further support these observations. A correlation between Deborah number and ROS is also presented.
17
Lionetto, Francesca, Francesco Montagna i Alfonso Maffezzoli. "Ultrasonic Dynamic Mechanical Analysis of Polymers". Applied Rheology 15, nr 5 (1.10.2005): 326–35. http://dx.doi.org/10.1515/arh-2005-0016.
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Abstract The propagation of ultrasonic waves in polymers depends on their viscoelastic behaviour and density, resulting significantly affected by phase transitions occurring with changing temperature and pressure or during chemical reactions. Therefore, the application of low intensity ultrasound, acting as a high frequency dynamic mechanical deformation applied to a polymer, can monitor the changes of viscoelastic properties associated with the glass transition, the crystallization, the physical or chemical gelation, the crosslinking. Thanks to the non-destructive character (due to the very small deformation amplitude), low intensity ultrasound can be successfully used for polymer characterization. Moreover, this technique has a big potential as a sensor for on-line and in-situ monitoring of production processes for polymers or polymer matrix composites. Recently, in the laboratory of Polymeric Materials of Lecce University a custom made ultrasonic set-up for the characterization of polymeric material, even at high temperatures, has been developed. The ultrasonic equipment is coupled with a rotational rheometer. Ultrasonic waves and shear oscillations at low frequency can be applied simultaneously on the sample, getting information on its viscoelastic behaviour over a wide frequency range. The aim of this paper is to present the potential and reliability of the ultrasonic equipment for the ultrasonic dynamic mechanical analysis (UDMA) of both thermosetting and thermoplastic polymers. Three applications of UDMA to different polymeric systems will be reviewed, concerning the cross-linking of a thermosetting resin, the crystallisation from melt of a semicrystalline polymer and the water sorption in a dry hydrogel film. From the ultrasonic velocity and attenuation measurements, the viscoelastic properties of the tested polymers are evaluated in terms of complex longitudinal modulus and compared with the results of conventional dynamic mechanical analysis, carried out at low frequency.
18
Roy, S., W. X. Xu, S. J. Park i K. M. Liechti. "Anomalous Moisture Diffusion in Viscoelastic Polymers: Modeling and Testing". Journal of Applied Mechanics 67, nr 2 (29.10.1999): 391–96. http://dx.doi.org/10.1115/1.1304912.
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It is now well known that Fick’s Law is frequently inadequate for describing moisture diffusion in polymers or polymer composites. Non-Fickian or anomalous diffusion typically occurs when the rates of diffusion and viscoelastic relaxation in a polymer are comparable, and the ambient temperature is below the glass transition temperature Tg of the polymer. As a result, it is necessary to take into account the time-dependent response of a polymer, analogous to viscoelastic relaxation of mechanical properties, in constructing such a model. In this paper, a simple yet robust methodology is proposed that would allow characterization of non-Fickian diffusion coefficients from moisture weight gain data for a polymer below its Tg. Subsequently, these diffusion coefficients are used for predicting moisture concentration profiles through the thickness of a polymer. Moisture weight gain data at different temperatures for an epoxy adhesive is employed to calibrate the model. Specimen thickness independence of the modeling parameters is established through comparison with test data. A finite element procedure that extends this methodology to more complex shapes and boundary conditions is also validated. [S0021-8936(00)02402-8]
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Ahola, Susanna, Petri Myllytie, Monika Österberg, Tuija Teerinen i Janne Laine. "Effect of polymer adsorption on cellulose nanofibril water binding capacity and aggregation". BioResources 3, nr 4 (20.10.2008): 1315–28. http://dx.doi.org/10.15376/biores.3.4.1315-1328.
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Polymer adsorption on cellulose nanofibrils and the effect on nanofibril water binding capacity were studied using cellulose nanofibril films together with quartz crystal microbalance with dissipation (QCM-D) and surface plasmon resonance (SPR). The experiments were performed in the immersed state, and special attention was paid to the effect of polymer properties on the water content and viscoelastic properties of the polymer/fibril layer. The dry mass of the adsorbed polymers was determined using SPR. The type of the adsorbed polymer strongly affected the water content and viscoelastic properties of the nanofibril film. The adsorption of a highly charged flocculating polymer, PDADMAC, caused dehydration of the film, which was also detected as nanofibril film stiffening. The adsorption of xyloglucan introduced a dispersing effect to the nanofibril film, which was detected as a loosening and softening of the nanofibril/polymer layer. A dispersing effect was also achieved with carboxymethyl cellulose (CMC), but CMC did not adsorb irreversibly on the nanofibril surfaces. In addition to the nanofibril film studies, the effect of polymer adsorption on cellulose nanofibril suspension aggregation was demonstrated using confocal laser scanning microscopy (CLSM). Xyloglucan was shown to open the nanofibril aggregate structures and act as a dispersing agent, whereas the other polymers studied did not have as significant an effect on aggregation.
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Yi, Sung, Nakyung Oh, Kyung-Eun Min, Je-Sik Shin i Cheolhee Kim. "Thermo-Viscoelastic Characterization of 3D Printing Polymers". Applied Sciences 13, nr 5 (23.02.2023): 2876. http://dx.doi.org/10.3390/app13052876.
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Polymer materials used in 3D printing exhibit degradation of material mechanical properties when exposed to thermal environments and thermal expansions can induce residual stresses in products or molds, which may result in dimensional instability and subsequent structural failures. In this study, based on linear thermo-viscoelastic principles, material degradation master curves, shift functions, and glass transition temperatures for four different polymers used for 3D printing techniques such as MultiJet Printing and Digital Lighting Process were measured by using a dynamic mechanical analyzer. Based on the single frequency test, the glass transition temperature was measured. In addition, dynamic measurements were carried out over a frequency range at isothermal condition and storage modulus vs. frequency curves were obtained. Then, the storage moduli curves measured at different temperatures were superposed into master curves using the frequency–temperature superposition principle and shift factors were calculated as a function of temperature. Subsequently, the complex moduli curves that were measured in the frequency were curve-fitted onto generalized Maxwell models by using the least squares method and the master curves of relaxation moduli at reference temperature were obtained. The effects of temperature, frequency, and time on dynamic moduli and relaxation behaviors of four polymers used for 3D printing were evaluated. Experimental results showed that Polymers C and D could be suitable to use at the service temperature above 100 °C and Polymer C was highly crosslinked and showed low modulus reduction after about a year. The master relaxation curves obtained through this process can be utilized to predict the long-term performance of polymer molds made by 3D printing at a given environmental condition.
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Zhong, Huiying, Qiuyuan Zang, Hongjun Yin i Huifen Xia. "Experimental Study on Medium Viscosity Oil Displacement Using Viscoelastic Polymer". Geofluids 2018 (29.11.2018): 1–11. http://dx.doi.org/10.1155/2018/4321380.
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With the growing demand for oil energy and a decrease in the recoverable reserves of conventional oil, the development of viscous oil, bitumen, and shale oil is playing an important role in the oil industry. Bohai Bay in China is an offshore oilfield that was developed through polymer flooding process. This study investigated the pore-scale displacement of medium viscosity oil by hydrophobically associating water-soluble polymers and purely viscous glycerin solutions. The role and contribution of elasticity on medium oil recovery were revealed and determined. Comparing the residual oil distribution after polymer flooding with that after glycerin flooding at a dead end, the results showed that the residual oil interface exhibited an asymmetrical “U” shape owing to the elasticity behavior of the polymer. This phenomenon revealed the key of elasticity enhancing oil recovery. Comparing the results of polymer flooding with that of glycerin flooding at different water flooding sweep efficiency levels, it was shown that the ratio of elastic contribution on the oil displacement efficiency increased as the water flooding sweep efficiency decreased. Additionally, the experiments on polymers, glycerin solutions, and brines displacement medium viscosity oil based on a constant pressure gradient at the core scale were carried out. The results indicated that the elasticity of the polymer can further reduce the saturation of medium viscosity oil with the same number of capillaries. In this study, the elasticity effect on the medium viscosity oil interface and the elasticity contribution on the medium viscosity oil were specified and clarified. The results of this study are promising with regard to the design and optimum polymers applied in an oilfield and to an improvement in the recovery of medium viscosity oil.
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WEERAPOL, Yotsanan, i Pornsak SRIAMORNSAK. "Differences in Viscoelasticity of Ophthalmic Polymer Solution after Sterilization". Walailak Journal of Science and Technology (WJST) 17, nr 7 (1.07.2020): 686–97. http://dx.doi.org/10.48048/wjst.2020.6341.
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Polymer solution has been used for increasing viscosity of ophthalmic solution in order to prolong the retention of active drug in the eye. The ophthalmic solution must be sterilized, which may affect the rheology properties of viscosity-inducing polymers. The aim of this study was to investigate the effect of sterilization treatment on viscosity-inducing agents (i.e., poloxamer, polyvinyl alcohol; (PVA), methyl cellulose (MC), polyvinylpyrrolidone (PVP) and carbomer). The effect of membrane filtration and steam sterilization or autoclaving (121 °C, 15 Ib/inch2, 15 min) were determined. A rheometer was used to investigate the viscosity and viscoelastic properties between treated and untreated polymer solutions. The power law model, consistency index (k), and power law index (n) of polymer solution viscosity were compared. For viscoelastic properties, storage modulus and loss modulus were examined. The results demonstrated that, viscosity of carbomer and MC solution (1 and 2 %) were changed after steam sterilization. No difference in viscosity was observed for PVP, PVA and poloxamer solution, between untreated and treated samples. The storage and loss moduli of PVA solution after autoclaving were not different when comparing with the untreated polymer solution. From this study, it could be concluded that the sterilization treatment influenced the viscosity behavior and viscoelastic properties of polymer solution used as viscosity-inducing agent in ophthalmic solution. Therefore, the selection of polymer and sterilization method should be carefully considered.
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Scotti, Andrea, Monia Brugnoni, Carlos G. Lopez, Steffen Bochenek, Jérôme J. Crassous i Walter Richtering. "Flow properties reveal the particle-to-polymer transition of ultra-low crosslinked microgels". Soft Matter 16, nr 3 (2020): 668–78. http://dx.doi.org/10.1039/c9sm01451a.
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Solutions of ultra-low crosslinked microgels show viscoelastic properties in between rigid particles and flexible polymers. The dominance of particle-like and polymer-like behavior depends on the concentration of microgel in solution.
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Echeverría, Coro, Miguel Rubio i Daniel López. "Thermo-Reversible Hybrid Gels Formed from the Combination of Isotactic Polystyrene and [Fe(II) (4-Octadecyl-1,2,4-Triazole)3(ClO4)2]n Metallo-Organic Polymer: Thermal and Viscoelastic Properties". Polymers 11, nr 6 (1.06.2019): 957. http://dx.doi.org/10.3390/polym11060957.
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Nano-sized one-dimensional metallo-organic polymers, characterized by the phenomenon of spin transition, are excellent candidates for advanced technological applications such as optical sensors, storage, and information processing devices. However, the main drawback of this type of polymers is their fragile mechanical properties, which hinders its processing and handling, and makes their practical use unfeasible. To overcome this problem, in this work, hybrid thermo-reversible gels are synthesized by combination of a metallo-organic polymer and isotactic polystyrene (iPS) in cis-decaline. A detailed investigation of the thermal and viscoelastic properties of the hybrid gels, in terms of iPS and metallo-organic polymer concentration is performed by means of differential scanning calorimetry and oscillatory rheology, respectively. From the analysis of the thermal properties, three transitions have been determined upon heating: Monotectic transition of the iPS gel, melting of the iPS gel, and melting of the metal-organic polymer gel, which suggest that the gels of the two polymers are formed independently in the hybrid gel, as long as the two polymers are in concentrations above the corresponding critical gelation concentrations. Results regarding viscoelastic properties and morphology confirmed that hybrid gels consisted of an interpenetrated network of polymer gels, formed by iPS and metallo-organic poymer gels growing independently.
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Ngai, K. L., i D. J. Plazek. "Identification of Different Modes of Molecular Motion in Polymers That Cause Thermorheological Complexity". Rubber Chemistry and Technology 68, nr 3 (1.07.1995): 376–434. http://dx.doi.org/10.5254/1.3538749.
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Abstract The viscoelastic properties of amorphous polymers are reviewed with emphasis on the glass to rubber dispersion (often referred to as the transition zone). Deviations from thermorheologieal simplicity (where molecular retardation and relaxation mechanisms have the same temperature dependence) are identified. Most theories and models of polymer chain dynamics do not address or acknowledge thermorheological complexities and correlations, such as that between the temperature dependence and the breadth of viscoelastic and dielectric dispersions of the local segmental motion. Without successful theories of these phenomena the understanding of polymer chain dynamics must be considered incomplete. In this review, old and new experimental data are used to identify the different modes of molecular motions and the domains of their contributions to the time and frequency dependence of the mechanical response of amorphous polymers. The different modes are then shown generally to have their own dependence on temperature. Thus the viscoelastic spectrum, including local segmental motions which dominate the onset of glassy behavior and largely determine the glass temperature, Tg, the glass to rubber softening dispersion, the rubbery plateau and the terminal zone, is thermorheologically complex. A coupling theory, with the physics of intermolecular interactions and cooperativity built into it, describes well the many-body dynamics of densely packed molecular systems such as polymers. The many predictions of the coupling theory are applied to the different viscoeleatic modes to explain the observed anomalous experimental facts and established correlations. The theoretical understanding has been improved to the extent that now a connection can be made between the chemical structure of the monomer and the viscoelastic properties of the polymer.
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Ellyin, Fernand, i Zihui Xia. "Nonlinear Viscoelastic Constitutive Model for Thermoset Polymers". Journal of Engineering Materials and Technology 128, nr 4 (9.05.2006): 579–85. http://dx.doi.org/10.1115/1.2345450.
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A nonlinear viscoelastic constitutive model, in differential form, is presented based on the deformation characteristics of thermoset polymers under complex loadings. This rheological model includes a criterion to delineate loading and unloading in multiaxial stress states, and different moduli for loading and unloading behaviors. The material constants and functions of this model are calibrated in accordance with a well-defined procedure. The model predictions are compared with the experimental data of an epoxy polymer subjected to uniaxial and biaxial stress states with monotonic and cyclic loading. The agreement is very good for various loading regimes. The constitutive model is further implemented in a finite element code and the residual stresses arising from the curing process of polymer reinforced composites is determined for two different epoxy resins.
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Utracki, L. A. "Viscoelastic behavior of polymer blends". Polymer Engineering and Science 28, nr 21 (listopad 1988): 1401–4. http://dx.doi.org/10.1002/pen.760282109.
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Chow, T. S. "Viscoelastic scaling in polymer gels". Macromolecular Theory and Simulations 7, nr 2 (1.03.1998): 257–61. http://dx.doi.org/10.1002/(sici)1521-3919(19980301)7:2<257::aid-mats257>3.0.co;2-7.
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OGAWA, F., J. KOYANAGI i H. KAWADA. "PMC-13: Characteristic of Nonlinear Viscoelastic Behavior in Vinylester Resin(PMC-II: POLYMERS AND POLYMER MATRIX COMPOSITES)". Proceedings of the JSME Materials and Processing Conference (M&P) 2005 (2005): 6. http://dx.doi.org/10.1299/jsmeintmp.2005.6_3.
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Amri, Nedjla, Djamila Ghemati, Nadia Bouguettaya i Djamel Aliouche. "Swelling Kinetics and Rheological Behavior of Chitosan-PVA / Montmorillonite Hybrid Polymers". Periodica Polytechnica Chemical Engineering 63, nr 1 (2.08.2018): 179–89. http://dx.doi.org/10.3311/ppch.12227.
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This study involved preparation of hybrid polymer systems based on chitosan-poly(vinyl alcohol) (PVA) blends and modified Montmorillonite. These structures were characterized through microscopy and infrared spectroscopy; swelling measurements were performed to explore polymer absorbency. The behavior of polymer systems was studied through steady and oscillatory shear rheology. Results showed that more stable blend membranes were formed due to the strong interaction between chitosan and PVA. The membranes exhibited appreciable water uptake and were sensitive to saline solution with a slight shrinking.Shear viscosity was described by Cross model to characterize non-Newtonian behavior of all polymer solutions, the shear thinning increases with PVA content, while viscosity increases with chitosan extent. In oscillatory experiments, it was observed that all measured viscoelastic properties were influenced by blends composition and clay content. For all samples, results show a typical behavior of an entangled system in the case of semi-dilute macromolecular viscoelastic fluids. The dynamic moduli exhibited higher values for blends, compared with values of neat polymers, which are an indication of a good stability and a tendency of gel formation. Therefore, the prepared chitosan-PVA systems, which exhibited high swelling degrees and suitable viscoelastic properties, have promising applications in tissue engineering and membrane processes.
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Matsumiya, Yumi, i Hiroshi Watanabe. "ENTANGLEMENT-LOOSENING DYNAMICS RESOLVED THROUGH COMPARISON OF DIELECTRIC AND VISCOELASTIC DATA OF TYPE-A POLYMERS: A REVIEW". Rubber Chemistry and Technology 93, nr 1 (1.01.2020): 22–62. http://dx.doi.org/10.5254/rct.19.80388.
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ABSTRACT For so-called type-A polymer chains having electrical dipoles aligned parallel along their backbone, the large-scale chain motion over the end-to-end distance results in not only viscoelastic but also dielectric relaxation. These two relaxation processes detect the same motion but with different averaging moments, which enables us to experimentally resolve some details of the chain dynamics through comparison of viscoelastic and dielectric data of type-A polymers. For a typical type-A polymer, high-cis polyisoprene (PI), results of such an experimental approach are summarized to discuss characteristic features of an entanglement-loosening process (constraint release and/or dynamic tube dilation process) resolved from the data comparison.
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Jingwei, Zhang, Li Jia, Huang Chuhao i Chen Shuo. "Study on dynamic viscoelastic constitutive model of nonwater reacted polyurethane grouting materials based on DMA". REVIEWS ON ADVANCED MATERIALS SCIENCE 61, nr 1 (1.01.2022): 238–49. http://dx.doi.org/10.1515/rams-2022-0004.
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Abstract Nonwater reacted polyurethane grouting materials are new materials developed to make up for the shortcomings of water-reactive materials in emergency rescue. However, its viscoelastic properties and constitutive model under dynamic loads have not been systematically studied. Based on dynamic thermal mechanical analysis (DMA), the dynamic viscoelastic indexes such as storage modulus, loss modulus, and loss factor of nonwater reacted polymer grouting material were obtained, and the frequency spectrum of polymer with different densities were analyzed. In addition, comparing and analyzing the classical viscoelastic constitutive models such as Maxewell model, Kelvin model, and Fractional model, the fourth-order generalized Maxwell model (GMM) was selected to construct the viscoelastic constitutive model of polyurethane grounding materials. Then, the parameters of the viscoelastic constitutive model of polyurethane grounding materials were obtained by using multi-objective shared parameter fitting method, and dynamic viscoelastic constitutive model of nonwater reacted polyurethane grouting materials was established. Furthermore, the viscoelastic constitutive model with different densities was verified by the DMA test. The results show that the dynamic viscoelastic constitutive model of nonwater reacted polyurethane grouting materials in the article can accurately and efficiently describe the dynamic viscoelastic properties of polyurethane grounding materials, which lays a foundation for the dynamic response analysis of polymer structures.
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Zhang, Jia, Shiqing Cheng, Jie Zhan i Qi Han. "The Effect of Rheology of Viscoelastic Polymer on Pressure Transient Response in Near-Wellbore Regions". Geofluids 2021 (7.06.2021): 1–12. http://dx.doi.org/10.1155/2021/5568336.
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Viscoelastic polymer solution shows shear thinning behavior at low shear rates and shear thickening behavior at high shear rates in reservoirs. However, models that ignored shear thickening behavior were commonly employed to interpret transient pressure data derived from tested wells in viscoelastic polymer flooding systems; although, viscoelastic polymer solutions show shear thickening behavior in the near-wellbore region due to high shear rate. To better characterize the oilfield with pressure transient analysis in viscoelastic polymer flooding systems, we developed a numerical model that takes into account both shear thinning behavior and shear thickening behavior. A finite volume method was employed to discretize partially differential flow equations in a hybrid grid system including PEBI mesh and Cartesian grid, and the Newton-Raphson method was used to solve the fully implicit nonlinear system. To illustrate the significance of our model, we compared our model with a model that ignores the shear thickening behavior by graphing their solutions on log-log plots. In the flow regime of near-wellbore damage, the pressure derivative computed by our model is distinctly larger than that computed by the model ignoring shear thickening behavior. Furthermore, the effect of shear thickening behavior on pressure derivative differs from that of near-wellbore damage. We then investigated the influence of shear thickening behavior on pressure derivative with different polymer injection rates, injection rates, and permeabilities. The results can provide a benchmark to better estimate near-wellbore damage in viscoelastic polymer flooding systems. Besides, we demonstrated the applicability and accuracy of our model by interpreting transient pressure data from a field case in an oilfield with viscoelastic polymer flooding treatments.
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Gbadamosi, Afeez, Shirish Patil, Muhammad Shahzad Kamal, Ahmad A. Adewunmi, Adeyinka S. Yusuff, Augustine Agi i Jeffrey Oseh. "Application of Polymers for Chemical Enhanced Oil Recovery: A Review". Polymers 14, nr 7 (31.03.2022): 1433. http://dx.doi.org/10.3390/polym14071433.
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Polymers play a significant role in enhanced oil recovery (EOR) due to their viscoelastic properties and macromolecular structure. Herein, the mechanisms of the application of polymeric materials for enhanced oil recovery are elucidated. Subsequently, the polymer types used for EOR, namely synthetic polymers and natural polymers (biopolymers), and their properties are discussed. Moreover, the numerous applications for EOR such as polymer flooding, polymer foam flooding, alkali–polymer flooding, surfactant–polymer flooding, alkali–surfactant–polymer flooding, and polymeric nanofluid flooding are appraised and evaluated. Most of the polymers exhibit pseudoplastic behavior in the presence of shear forces. The biopolymers exhibit better salt tolerance and thermal stability but are susceptible to plugging and biodegradation. As for associative synthetic polyacrylamide, several complexities are involved in unlocking its full potential. Hence, hydrolyzed polyacrylamide remains the most coveted polymer for field application of polymer floods. Finally, alkali–surfactant–polymer flooding shows good efficiency at pilot and field scales, while a recently devised polymeric nanofluid shows good potential for field application of polymer flooding for EOR.
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Lebahn, Kerstin, Thomas Kleine, Nicklas Fiedler, Daniela Arbeiter i Niels Grabow. "Evaluation of a nonlinear viscoelastic-plastic constitutive model in numerical simulation of thermoplastic polymers for stent application". Current Directions in Biomedical Engineering 8, nr 2 (1.08.2022): 470–73. http://dx.doi.org/10.1515/cdbme-2022-1120.
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Abstract To simulate the specific material properties of thermoplastic polymers a suitable constitutive model is essential. The parallel rheological framework (PRF) model was calibrated and evaluated in this study as potential constitutive model for polymer stent application. Tensile as well as recovery tests with different loading rates were performed using PLLA specimens. In order to calibrate the constitutive model, the conducted material tests were simulated accordingly. The parameters of the model were iteratively varied to obtain good accordance of the simulation with the material tests. In contrast to elastic plastic material models, viscoelastic material behavior can be represented with the nonlinear viscoelastic-plastic PRF model. The generated and possibly further refined model can be used for the simulation of polymer stents.
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Raghavan, Sathyanarayanan, Raphael I. Okereke i Suresh K. Sitaraman. "An Efficient Implementation of Polymer Viscoelastic Behavior Through a Pseudo Viscoelastic Model". Journal of Microelectronics and Electronic Packaging 8, nr 2 (1.04.2011): 83–87. http://dx.doi.org/10.4071/imaps.285.
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Modeling of viscoelastic relaxation of polymer materials is important to understand the thermo-mechanical behavior of organic microelectronic systems. However, incorporation of viscoelastic behavior into numerical models makes the models compute-intensive. This paper presents a different technique to incorporate the polymer viscoelastic behavior into the numerical models such that the computation time is not adversely affected without compromising the accuracy of the results obtained. In the proposed “pseudo viscoelastic” modeling technique, the modulus of the viscoelastic material is computed as a function of time and temperature loading history outside of the finite-element simulation, and is then input into the simulation as a thermo-elastic material incorporating the viscoelastic relaxation of the material. This paper compares the warpage results obtained through the proposed technique against a complete viscoelastic simulation model and experimental data, and it is seen that the maximum warpage predicted using the proposed technique agree within 10% compared with the results obtained from a “full” viscoelastic model. Also, it is shown through some of our simulations that the proposed technique could result in a computational time saving of more than 50% and hard disk space saving of 65%.
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Badagliacco, Dionisio, i Antonino Valenza. "Viscoelastic Behavior of an Epoxy Resin Modified with Recycled Waste Particles Analyzed through a Fractional Model". Processes 9, nr 10 (14.10.2021): 1826. http://dx.doi.org/10.3390/pr9101826.
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It is well-known that the addition of randomly dispersed particles in polymers influences their linear viscoelastic behavior and dynamic mechanical properties. The aim of this study was to describe the viscoelastic behavior of an epoxy resin modified by waste glass and rubber particles using the linear fractional spring-pot model. Unlike complex classical exponential models, fractional models, being only two-parameter dependent, make it easier to characterize the viscoelastic behavior of materials. Isothermal relaxation and single frequency sweep temperature dynamic tests were carried out in a dynamic mechanical analyzer DMA150 by varying the content of the particles from 0 to 20% by weight. Overall, the results of this study evidence that using waste materials as additives for polymer compounds is a practical and sustainable possibility when it comes to modifying their viscoelastic properties.
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Zhong, Huiying, Weidong Zhang, Hongjun Yin i Haoyang Liu. "Study on Mechanism of Viscoelastic Polymer Transient Flow in Porous Media". Geofluids 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/8763951.
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Oil recovery, including conventional and viscous oil, can be improved significantly by flooding with polymer solutions. This chemical flooding method can increase oil production, and it can improve the macrodisplacement efficiency and microsweep efficiencies. In this study, we establish physical models that include the dead-end and complex models based on the pore-network pattern etched into glass, using the snappyHexMesh solver in OpenFOAM. These models capture the complexity and topology of porous media geometry. We establish a mathematical model for transient flows of viscoelastic polymers using computational fluid dynamics simulations, and we study the distributions of pressure and velocity for different elasticity scenarios and different flooding process. The results demonstrate that the pressure difference increases as the relaxation time decreases, before the flow reaches its steady state. For a steady flow, elasticity can give rise to an additional pressure difference, which increases with increasing elasticity. Thus, the characteristics of pressure difference vary before and after the flow becomes steady; this phenomenon is very important. Velocity contours become more widely spaced with elasticity increase. This suggests that elasticity of the polymer solutions contributes to the microsweep efficiency. The results of the study provide the necessary theoretical foundation for laboratory experiments and development of methods for polymer flooding and can be helpful for the design and selection of polymers for polymer flooding.
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Ahmad, Daniel, Nahiene Hamila, Khalid Lamnawar i Philippe Boisse. "Mechanical Analysis and Simulation of the Thermoforming Process of Thin Polymer Sheets". Key Engineering Materials 504-506 (luty 2012): 1111–16. http://dx.doi.org/10.4028/www.scientific.net/kem.504-506.1111.
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Most of industrial processes (thermoforming, injection moulding...) require the understanding of thermo-mechanical behaviour of polymeric sheets. Furthermore, the mastery of the deformation of the polymers becomes an important stake. In order to improve and complete the understanding of the deformation of thermoplastic polymer materials during their forming processes, the problem of modelling the thermoforming process for viscoelastic sheet under large strains is considered. The first step of the process that consists in heating the sheet using infrared lamps is taken into account by included a temperature field in viscoelastic behaviour laws under integral forms. The finite element simulation of the different steps will be presented
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Niedziela, D., A. Latz i O. Iliev. "Simulations of Viscoelastic Polymer Solution Flows". NAFEMS International Journal of CFD Case Studies 6 (marzec 2007): 15–25. http://dx.doi.org/10.59972/d8hd7bkp.
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Many natural and synthetic fluids are viscoelastic materials i.e. the stress at a certain fluid particle depends upon the history of the deformation experienced by that particle. Polymer melts and most polymer solutions are examples of such liquids. Simulation of the flow of these fluids is therefore of great interest for the plastic industry. Viscoelastic fluids are examples of non - Newtonian fluids. While the Newtonian fluids are characterised by a constant viscosity (i.e., constant ratio between shear stress and the rate of strain), the non-Newtonian fluids require more complicated constitutive relations in order to close the governing system of equations...
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Losi, Giancarlo U., i Wolfgang G. Knauss. "Thermal Stresses in Nonlinearly Viscoelastic Solids". Journal of Applied Mechanics 59, nr 2S (1.06.1992): S43—S49. http://dx.doi.org/10.1115/1.2899506.
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Three different rheological models are applied to the study of transient and residual thermal stresses in amorphous polymers cooled across the glass transition. The models differ mainly in their treatments of the nonequilibrium (time-dependent) portion of the morphological changes in the polymer and their influence on the relaxation process. The interstitial volume between polymer chains (free volume) is found to play an important role in the residual stresses; they are affected by the relative time scale of thermal diffusion and thermoviscoelastic relaxation/creep. This result has implications for injection molded parts of different section dimensions and for extrusion products. This fact must also be accounted for in determining the thermomechanicalproperties in the glass transition range. The step cooling ofPVAc spheres (1 and 20 mm dia.) and a cylinder (20 mm dia.) have been considered; most of the results presented apply to the sphere(s). Residual stresses can vary by as much as 100percent depending on whether the interstitial molecular (free) volume is counted or not. It is also demonstrated that residual stresses can be higher than an elastic analysis based on the glassy properties would suggest; thus the “stressfree temperature” is found to be significantly above the glass transition.
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Liu, Jia-Jia, Li-Li Wu i Ting Chen. "Investigation on the Polymer Drawing Model of the Centrifugal Spinning". Recent Patents on Nanotechnology 14, nr 1 (24.04.2020): 21–26. http://dx.doi.org/10.2174/1872210513666190801110145.
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Background and Objective: Some patents have reported the centrifugal spinning method which utilizes the centrifugal force produced by a high speed rotating device to fabricate fibers from polymer melts or solutions. Recently, with the development of technologies, centrifugal spinning was employed to produce ultrafine fibers and nanofibers. In order to improve the equipment and technology of centrifugal spinning and obtain finer fibers, it is important to model the polymer drawing of the centrifugal spinning. Methods: The polymer drawing in the centrifugal spinning is modeled and simulated. The force balance equation and heat transfer balance equation are established after analyzing the motion and heat transfer of the polymer melts. These nonlinear equations are solved based on the least square method to obtain the radius of excircle and the shape of streamline. A fourth order Runge-Kutta method is utilized to obtain the diameter and temperature of the threadline because there are initial value problems of first order ordinary differential equations. Streamlines and diameter of polymer melts at different viscoelasticities and different spinning temperatures are obtained. The simulation results are compared with the measured results to verify the polymer drawing model. Results: The viscoelastic force in the centrifugal spinning changes constantly at a fixed rotation speed of the rotating spinneret. As the spinneret is rotating, the radius of excircle R1 increases slowly when the time passes, which means the viscoelastic force decreases slowly. The change of the viscoelastic force accelerates the increase of the radius vector. The simulation results show that the threadline diameter under the condition of changing viscoelastic forces is smaller than that under the condition of fixed visoelastic forces. The temperature of the polymer melts decreases faster under the condition of changing viscoelastic forces than that under the condition of fixed visoelastic forces. The threadline diameter decreases with the increase of the rotation speed. Higher initial polymer temperatures yield smaller fiber diameters. Conclusion: The polymer drawing in the centrifugal spinning is modeled and simulated. The simulation results tally with the measured results confirming the effectiveness of the polymer drawing model. The simulation results show that the change of the viscoelastic force is favorable to the polymer drawing and both larger rotation speeds and higher initial polymer temperatures can produce finer fibers, which lays a good foundation for the computer-assisted design of the centrifugal spinning.
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Gupta, V., S. Roy i L. R. Dharani. "Multi-Scale Modelling of Long-Term Mechanical Behaviour in Polymer Composite Laminates with Woven Fibre Architecture". Polymers and Polymer Composites 9, nr 5 (lipiec 2001): 297–317. http://dx.doi.org/10.1177/096739110100900501.
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A comprehensive analytical model for predicting the long-term durability of polymers and polymer matrix composites should in general take into account polymer viscoelastic/viscoplastic creep, hygrothermal effects, and the effects of physical and chemical ageing on material response. These effects, in turn are influenced by a multitude of factors such as polymer morphology, service temperature, ambient relative humidity, internal moisture concentrations, stacking sequence, fibre volume fraction, fibre architecture, applied stress level, degree of damage and ageing time. The primary objective of this paper is to present a multi-scale modelling methodology to simulate the long-term interlaminar properties in polymer matrix woven composites and then predict the critical regions where failure is most likely to occur. A micro-mechanics approach towards modelling the out-of-plane viscoelastic behaviour of a five-harness satin woven-fibre cross-ply composite laminate is presented, taking into consideration the weave architecture and time-dependent effects. In-plane properties are assumed to be dominated by the carbon fibres and are hence deemed elastic. The classical lamination theory model proposed by Raju and Wang is adapted to include the in-plane elastic behaviour of woven fibre composites. For the matrixdominated out-of-plane response, a viscoelastic creep model is employed to model the resin, based on Schapery's nonlinear viscoelastic constitutive law. In addition, physical ageing of the matrix has been included in the model, using the effective time theory proposed by Struik. Furthermore, the effect of large deflections and rotations on the time dependent out-of-plane behaviour is also investigated using the micro-mechanics model. The homogenized in-plane and out-of-plane compliance obtained using the proposed micro-mechanics methodology could be applied within the framework of a structural finite element code to model the macro-scale long-term behaviour of a woven fabric composite structure.
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Reinas Dos Santos André, José, i José Joaquim C. Cruz Pinto. "Creep Behaviour of Viscoelastic Polymer Materials". Materials Science Forum 455-456 (maj 2004): 759–62. http://dx.doi.org/10.4028/www.scientific.net/msf.455-456.759.
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Dewitt, Leilani, i Wayne T. Reader. "Viscoelastic polymer temperature‐frequency shift functions." Journal of the Acoustical Society of America 90, nr 4 (październik 1991): 2294. http://dx.doi.org/10.1121/1.401104.
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Harden, J. L., i H. Pleiner. "Hydrodynamic modes of viscoelastic polymer films". Physical Review E 49, nr 2 (1.02.1994): 1411–23. http://dx.doi.org/10.1103/physreve.49.1411.
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Srivastava, Iti, Zhong-Zhen Yu i NikhilA Koratkar. "Viscoelastic Properties of Graphene-Polymer Composites". Advanced Science, Engineering and Medicine 4, nr 1 (1.02.2012): 10–14. http://dx.doi.org/10.1166/asem.2012.1127.
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Luo, K., W. Gronski i C. Friedrich. "Viscoelastic phase separation in polymer blends". European Physical Journal E 15, nr 2 (październik 2004): 177–87. http://dx.doi.org/10.1140/epje/i2003-10158-7.
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Watanabe, Hiroshi. "Viscoelastic properties of concentrated polymer systems." Kobunshi 35, nr 12 (1986): 1110–13. http://dx.doi.org/10.1295/kobunshi.35.1110.
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Lesueur, Didier, Jean-François Gérard, Pierre Claudy, Jean-Marie Létoffé, Didier Martin i Jean-Pascal Planche. "Polymer modified asphalts as viscoelastic emulsions". Journal of Rheology 42, nr 5 (wrzesień 1998): 1059–74. http://dx.doi.org/10.1122/1.550918.
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