The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
John M Dealy - One of the best experts on this subject based on the ideXlab platform.
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use of a sliding Plate Rheometer to measure the first normal stress difference at high shear rates
Rheologica Acta, 2007Co-Authors: Junke Xu, John M Dealy, Stephane Costeux, Mark N De DeckerAbstract:The use of a sliding Plate Rheometer (SPR) to determine the first normal stress difference of molten polymers and elastomers at high shear rates is demonstrated. The simple shear flow in this instrument is not subject to the flow instabilities that limit the use of rotational Rheometers to shear rates often below 1 s−1. However, issues of secondary flow and wall slip must be addressed to obtain reliable data using an SPR. A highly entangled, monodisperse polybutadiene and a commercial polystyrene were the polymers studied. The inclusion of the polystyrene made it possible to compare data with those obtained by Lodge using a stressmeter, which is an instrument based on the measurement of the hole pressure. The data from the two instruments are in good agreement and are also close to the predictions of an empirical equation of Laun based on the storage and loss moduli.
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a high pressure sliding Plate Rheometer for polymer melts
Journal of Rheology, 1999Co-Authors: Francois Koran, John M DealyAbstract:A high-pressure sliding Plate Rheometer has been developed to investigate the effect of pressure on the rheological behavior of molten polymers and elastomers. The new Rheometer operates at pressures up to 70 MPa and temperatures up to 225 °C. The sample is subjected to simple shear, and the resulting shear stress is measured locally using a shear stress transducer. This design eliminates the inhomogeneities in pressure and shear rate that occur in high pressure capillary and slit Rheometers. Preliminary evaluation of the new instrument was carried out using a linear low density polyethylene. Viscosity curves were generated at pressures ranging from atmospheric pressure to 70 MPa, and the pressure coefficient of viscosity was determined. Experiments were also carried out in step strain and large amplitude oscillatory shear, demonstrating the new Rheometer’s use to study the nonlinear viscoelastic behavior of molten polymers. Finally, this instrument was used to study strain-induced crystallization.
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frequency response of a shear stress transducer installed in a sliding Plate Rheometer
Journal of Rheology, 1998Co-Authors: John M Dealy, Ranjit S JeyaseelanAbstract:A number of laboratories are currently using sliding Plate Rheometers equipped with shear stress transducers to study the nonlinear viscoelasticity and slip of molten polymers. In making such measurements, it is sometimes essential to know to what degree the dynamic response of the shear stress transducer itself is influencing the output signal. Experiments should be designed to minimize this effect, but some attenuation and phase shift is inevitable because of the presence of polymer inside the transducer. We have measured the dynamic response of a shear stress transducer in situ in a sliding Plate Rheometer for two molten polyethylenes. We have also developed a model for the transducer response. In oscillatory shear experiments above a frequency of 1 Hz, the amplitude ratio and phase lead are significant for both materials studied.
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sliding Plate Rheometer studies of concentrated polystyrene solutions nonlinear viscoelasticity and wall slip of two high molecular weight polymers in tricresyl phosphate
Journal of Rheology, 1998Co-Authors: Michael J Reimers, John M DealyAbstract:Two high molecular weight, narrow distribution polystyrenes dissolved in tricresyl phosphate were studied using a sliding Plate Rheometer. Shear stress and birefringence measurements in step strain allowed the determination of N3 for both solutions. Start-up of steady simple shear and large amplitude oscillatory shear measurements revealed that the critical shear stress for slip for both solutions is around 2500 Pa and that slip is dynamic in nature, allowing rheological measurements above the critical stress to be made at sufficiently high frequencies. The critical stress value was used in conjunction with data from the literature to develop a relationship between critical stress and concentration. Large-amplitude oscillatory shear stress measurements revealed that the solutions exhibit a limiting behavior at high strain rate amplitudes in the intermediate frequency range when the dependence on strain rate amplitude becomes small. Birefringence measurements showed that at high frequencies, where the time scale of the deformation is short, the oscillatory component of N3 vanished. This was found to occur at lower frequencies for the lower molecular weight solution. In contrast, the average value of the third normal stress difference, reflected in the zeroth harmonic, was found to vary little between the two solutions.Two high molecular weight, narrow distribution polystyrenes dissolved in tricresyl phosphate were studied using a sliding Plate Rheometer. Shear stress and birefringence measurements in step strain allowed the determination of N3 for both solutions. Start-up of steady simple shear and large amplitude oscillatory shear measurements revealed that the critical shear stress for slip for both solutions is around 2500 Pa and that slip is dynamic in nature, allowing rheological measurements above the critical stress to be made at sufficiently high frequencies. The critical stress value was used in conjunction with data from the literature to develop a relationship between critical stress and concentration. Large-amplitude oscillatory shear stress measurements revealed that the solutions exhibit a limiting behavior at high strain rate amplitudes in the intermediate frequency range when the dependence on strain rate amplitude becomes small. Birefringence measurements showed that at high frequencies, where the time...
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sliding Plate Rheometer studies of concentrated polystyrene solutions large amplitude oscillatory shear of a very high molecular weight polymer in diethyl phthalate
Journal of Rheology, 1996Co-Authors: Michael J Reimers, John M DealyAbstract:A very high molecular weight, narrow molecular weight distribution polystyrene, having a molecular weight of 8.42×106, was investigated using a sliding Plate Rheometer. The solvent was diethyl phthalate. The solution exhibited wall slip during steady shear, even at very low shear rates and exhibited a marked normal‐stress‐driven secondary flow at high shear rates. However, there was no evidence of slip during the oscillatory shear tests. Using fast Fourier transform analysis, the results of the oscillatory shear tests on this solution are presented in terms of response surfaces in a space based on a Pipkin diagram (strain‐rate amplitude versus frequency). These reveal the linear and nonlinear regimes and the approach to a purely elastic regime at high frequencies. Wagner’s constitutive equation predicts the major trends in the experimental data but does not provide quantitative predictions over the entire range of experimental parameters.
Jyhhorng Wang - One of the best experts on this subject based on the ideXlab platform.
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Characterization of UHMWPE sol–gel transition by parallel Plate Rheometer and pulsed NMR
Polymer, 1999Co-Authors: Hsientang Chiu, Jyhhorng WangAbstract:Abstract The gel point and characterization of sol–gel transition of UHMWPE/decalin systems were investigated. In this study rheological method and DSC method were used to measure the gel point of UHMWPE gel at various concentrations. The result showed that the gel point increased with increasing gel concentration. Meanwhile pulsed NMR was also utilized to investigate 6 wt% UHMWPE gel. It was found that when sol–gel transition temperature was approximately 100°C, large amount of UHMWPE gel turned into solution state. Therefore, it produced re-entanglement and increased the random region within the UHMWPE molecular chain, which led to the decrease of interaction force among the polymer.
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characterization of uhmwpe sol gel transition by parallel Plate Rheometer and pulsed nmr
Polymer, 1999Co-Authors: Hsientang Chiu, Jyhhorng WangAbstract:Abstract The gel point and characterization of sol–gel transition of UHMWPE/decalin systems were investigated. In this study rheological method and DSC method were used to measure the gel point of UHMWPE gel at various concentrations. The result showed that the gel point increased with increasing gel concentration. Meanwhile pulsed NMR was also utilized to investigate 6 wt% UHMWPE gel. It was found that when sol–gel transition temperature was approximately 100°C, large amount of UHMWPE gel turned into solution state. Therefore, it produced re-entanglement and increased the random region within the UHMWPE molecular chain, which led to the decrease of interaction force among the polymer.
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a study of rheological behavior of a polypyrrole modified uhmwpe gel using a parallel Plate Rheometer
Polymer Engineering and Science, 1999Co-Authors: Hsientang Chiu, Jyhhorng WangAbstract:Polypyrrole powder was added to a 6% UHMWPE decalin solution as an interfacial modifier. Rheological properties and dynamic viscoelastic properties, including shear viscosity, shear storage modulus (G′), and shear loss modulus (G″), were measured with a parallel Plate Rheometer using rotation and oscillation modes. The results show that these properties increase with the PPy content. In addition, the gelation temperature decreased with increasing PPy content. This suggests that the presence of PPy enhanced the entanglement network in the solution, which is similar to the role of filler in rubber.
Ranjit S Jeyaseelan - One of the best experts on this subject based on the ideXlab platform.
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frequency response of a shear stress transducer installed in a sliding Plate Rheometer
Journal of Rheology, 1998Co-Authors: John M Dealy, Ranjit S JeyaseelanAbstract:A number of laboratories are currently using sliding Plate Rheometers equipped with shear stress transducers to study the nonlinear viscoelasticity and slip of molten polymers. In making such measurements, it is sometimes essential to know to what degree the dynamic response of the shear stress transducer itself is influencing the output signal. Experiments should be designed to minimize this effect, but some attenuation and phase shift is inevitable because of the presence of polymer inside the transducer. We have measured the dynamic response of a shear stress transducer in situ in a sliding Plate Rheometer for two molten polyethylenes. We have also developed a model for the transducer response. In oscillatory shear experiments above a frequency of 1 Hz, the amplitude ratio and phase lead are significant for both materials studied.
Hsientang Chiu - One of the best experts on this subject based on the ideXlab platform.
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Characterization of UHMWPE sol–gel transition by parallel Plate Rheometer and pulsed NMR
Polymer, 1999Co-Authors: Hsientang Chiu, Jyhhorng WangAbstract:Abstract The gel point and characterization of sol–gel transition of UHMWPE/decalin systems were investigated. In this study rheological method and DSC method were used to measure the gel point of UHMWPE gel at various concentrations. The result showed that the gel point increased with increasing gel concentration. Meanwhile pulsed NMR was also utilized to investigate 6 wt% UHMWPE gel. It was found that when sol–gel transition temperature was approximately 100°C, large amount of UHMWPE gel turned into solution state. Therefore, it produced re-entanglement and increased the random region within the UHMWPE molecular chain, which led to the decrease of interaction force among the polymer.
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characterization of uhmwpe sol gel transition by parallel Plate Rheometer and pulsed nmr
Polymer, 1999Co-Authors: Hsientang Chiu, Jyhhorng WangAbstract:Abstract The gel point and characterization of sol–gel transition of UHMWPE/decalin systems were investigated. In this study rheological method and DSC method were used to measure the gel point of UHMWPE gel at various concentrations. The result showed that the gel point increased with increasing gel concentration. Meanwhile pulsed NMR was also utilized to investigate 6 wt% UHMWPE gel. It was found that when sol–gel transition temperature was approximately 100°C, large amount of UHMWPE gel turned into solution state. Therefore, it produced re-entanglement and increased the random region within the UHMWPE molecular chain, which led to the decrease of interaction force among the polymer.
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a study of rheological behavior of a polypyrrole modified uhmwpe gel using a parallel Plate Rheometer
Polymer Engineering and Science, 1999Co-Authors: Hsientang Chiu, Jyhhorng WangAbstract:Polypyrrole powder was added to a 6% UHMWPE decalin solution as an interfacial modifier. Rheological properties and dynamic viscoelastic properties, including shear viscosity, shear storage modulus (G′), and shear loss modulus (G″), were measured with a parallel Plate Rheometer using rotation and oscillation modes. The results show that these properties increase with the PPy content. In addition, the gelation temperature decreased with increasing PPy content. This suggests that the presence of PPy enhanced the entanglement network in the solution, which is similar to the role of filler in rubber.
Jeanmarie Aubry - One of the best experts on this subject based on the ideXlab platform.
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cone Plate Rheometer as reactor and viscosity probe for the detection of transitional phase inversion of brij30 isopropyl myristate water model emulsion
Industrial & Engineering Chemistry Research, 2016Co-Authors: Christel Pierlot, Jesus F Ontiveros, Marianne Catte, Jeanlouis Salager, Jeanmarie AubryAbstract:Brij30/isopropyl myristate/water model emulsions were used to study the inversion morphology change from O/W to W/O. The transitional phase inversion was detected by monitoring the electrical conductivity during a heating–cooling cycle while the viscosity of the emulsion was followed under constant shear rate with a cone–Plate Rheometer equipment. The two methods provide similar values of phase inversion temperature. However, different rheological profiles are observed depending on the surfactant concentration and water fraction. Viscosity maps of formulation-composition maps (specifically temperature–surfactant concentration and temperature–water fraction) pointed to the occurrence of both transitional and catastrophic inversion processes. A complete formulation–composition map with all different emulsion morphologies and isoviscosities contours for the 9% Brij30/IPM/water is presented. The use of a commercial cone–Plate Rheometer exhibits several advantages over the classical conductivity measurement; i...
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Cone–Plate Rheometer as Reactor and Viscosity Probe for the Detection of Transitional Phase Inversion of Brij30–Isopropyl Myristate–Water Model Emulsion
Industrial & Engineering Chemistry Research, 2016Co-Authors: Christel Pierlot, Jesus F Ontiveros, Marianne Catte, Jeanlouis Salager, Jeanmarie AubryAbstract:Brij30/isopropyl myristate/water model emulsions were used to study the inversion morphology change from O/W to W/O. The transitional phase inversion was detected by monitoring the electrical conductivity during a heating–cooling cycle while the viscosity of the emulsion was followed under constant shear rate with a cone–Plate Rheometer equipment. The two methods provide similar values of phase inversion temperature. However, different rheological profiles are observed depending on the surfactant concentration and water fraction. Viscosity maps of formulation-composition maps (specifically temperature–surfactant concentration and temperature–water fraction) pointed to the occurrence of both transitional and catastrophic inversion processes. A complete formulation–composition map with all different emulsion morphologies and isoviscosities contours for the 9% Brij30/IPM/water is presented. The use of a commercial cone–Plate Rheometer exhibits several advantages over the classical conductivity measurement; i...