Adib Ahmadzadegan, H. Mitra, P. Vlachos, A. Ardekani
We present a novel approach to perform passive microrheology. A method to measure the rheological properties of fluids from the Brownian motion of suspended particles. Rheological properties are found from the particles' mean square displacements (MSDs) as a function of measurement time lag. Current state-of-the-art approaches find the MSD by tracking multiple particles' trajectories. However, particle tracking approaches face many limitations, including low accuracy and high computational cost, and they are only applicable to low particle seeding densities. Here, we present a novel method, termed particle image rheometry (PIR), for estimating the particle ensemble MSD from the temporal evolution of the probability density function of the displacement as a function of measurement time lag. First, the probability density function (PDF) of the particle displacements for each time lag is found using a generalized ensemble image cross-correlation approach that eliminates the need for particle tracking. Then, PDFs are used to calculate the MSD from which the complex viscosity of the solution is measured. We evaluate the performance of PIR using synthetic datasets and show that it can achieve an error of less than 1% in passive microrheology measurements, which corresponds to a twofold lower error than existing methods. Finally, we compare the measured complex viscosity from PIR with bulk rheometry for a polymeric solution and show agreement between the two measurements.
{"title":"Particle Image micro-Rheology (PIR) using displacement probability density function","authors":"Adib Ahmadzadegan, H. Mitra, P. Vlachos, A. Ardekani","doi":"10.1122/8.0000629","DOIUrl":"https://doi.org/10.1122/8.0000629","url":null,"abstract":"We present a novel approach to perform passive microrheology. A method to measure the rheological properties of fluids from the Brownian motion of suspended particles. Rheological properties are found from the particles' mean square displacements (MSDs) as a function of measurement time lag. Current state-of-the-art approaches find the MSD by tracking multiple particles' trajectories. However, particle tracking approaches face many limitations, including low accuracy and high computational cost, and they are only applicable to low particle seeding densities. Here, we present a novel method, termed particle image rheometry (PIR), for estimating the particle ensemble MSD from the temporal evolution of the probability density function of the displacement as a function of measurement time lag. First, the probability density function (PDF) of the particle displacements for each time lag is found using a generalized ensemble image cross-correlation approach that eliminates the need for particle tracking. Then, PDFs are used to calculate the MSD from which the complex viscosity of the solution is measured. We evaluate the performance of PIR using synthetic datasets and show that it can achieve an error of less than 1% in passive microrheology measurements, which corresponds to a twofold lower error than existing methods. Finally, we compare the measured complex viscosity from PIR with bulk rheometry for a polymeric solution and show agreement between the two measurements.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41703919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Angelini, D. Larobina, B. Ruzicka, F. Greco, R. Pastore
The occurrence of non-equilibrium transitions between arrested states has recently emerged as an intriguing issue in the field of soft glassy materials. The existence of one such transition has been suggested for aging colloidal clays (Laponite® suspensions) at a weight concentration of 3.0%, although further experimental evidences are necessary to validate this scenario. Here, we test the occurrence of this transition for spontaneously aged (non-rejuvenated) samples by exploiting the rheological tools of dynamical mechanical analysis. On imposing consecutive compression cycles to differently aged clay suspensions, we find that quite an abrupt change of rheological parameters occurs for ages around three days. For Young’s and elastic moduli, the change with the waiting time is essentially independent from the deformation rate, whereas other “fluid-like” properties, such as the loss modulus, do clearly display some rate dependence. We also show that the crossover identified by rheology coincides with deviations of the relaxation time (obtained through x-ray photon correlation spectroscopy) from its expected monotonic increase with aging. Thus, our results robustly support the existence of a glass-glass transition in aging colloidal clays, highlighting characteristic features of their viscoelastic behavior.
{"title":"Rheological signatures of a glass-glass transition in an aging colloidal clay","authors":"R. Angelini, D. Larobina, B. Ruzicka, F. Greco, R. Pastore","doi":"10.1122/8.0000592","DOIUrl":"https://doi.org/10.1122/8.0000592","url":null,"abstract":"The occurrence of non-equilibrium transitions between arrested states has recently emerged as an intriguing issue in the field of soft glassy materials. The existence of one such transition has been suggested for aging colloidal clays (Laponite® suspensions) at a weight concentration of 3.0%, although further experimental evidences are necessary to validate this scenario. Here, we test the occurrence of this transition for spontaneously aged (non-rejuvenated) samples by exploiting the rheological tools of dynamical mechanical analysis. On imposing consecutive compression cycles to differently aged clay suspensions, we find that quite an abrupt change of rheological parameters occurs for ages around three days. For Young’s and elastic moduli, the change with the waiting time is essentially independent from the deformation rate, whereas other “fluid-like” properties, such as the loss modulus, do clearly display some rate dependence. We also show that the crossover identified by rheology coincides with deviations of the relaxation time (obtained through x-ray photon correlation spectroscopy) from its expected monotonic increase with aging. Thus, our results robustly support the existence of a glass-glass transition in aging colloidal clays, highlighting characteristic features of their viscoelastic behavior.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44420073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Liu, M. Hildner, Omkar Roy, William A. Van den Bogert, James H. Lorenz, Maude Desroches, K. Koppi, A. Shih, Ronald G. Larson
Direct ink writing is used to print multiple polydimethylsiloxane (PDMS) mixtures with fumed silica or as a two-part commercial liquid silicone rubber (LSR) mixed with polyethylene glycol (PEG) or as a two-part commercial vulcanizing (RTV) silicone. We correlate their printability into a hollow slump cone with rheological measurements, including (1) a shear rate up-ramp followed by (2) a down-ramp in the shear rate, (3) creep tests, and (4) large-amplitude oscillatory shear (LAOS) with increasing amplitude. The PDMS-fumed silica mixtures fail to print even at the highest fumed silica loading used (9 wt. %), while LSR-PEG with 4 or 6 wt. % PEG prints well, and one of the two RTV silicone components is printable, as is the mixture due in part to its rapid chemical curing. The large differences in printability of these materials do not correlate well with any single rheological test. They do correlate with a combination of a measure of material strength, given by either the yield stress σycr from creep tests or the “flow stress” σf at which G′ and G″ cross-over in LAOS, and of material recoverability given by the dynamic yield stress σy− in test 2. The latter is measured during a down-ramp in the shear rate after reaching a maximum shear rate of 1000 s−1, the highest shear rate in the print nozzle.
{"title":"On the selection of rheological tests for the prediction of 3D printability","authors":"Y. Liu, M. Hildner, Omkar Roy, William A. Van den Bogert, James H. Lorenz, Maude Desroches, K. Koppi, A. Shih, Ronald G. Larson","doi":"10.1122/8.0000612","DOIUrl":"https://doi.org/10.1122/8.0000612","url":null,"abstract":"Direct ink writing is used to print multiple polydimethylsiloxane (PDMS) mixtures with fumed silica or as a two-part commercial liquid silicone rubber (LSR) mixed with polyethylene glycol (PEG) or as a two-part commercial vulcanizing (RTV) silicone. We correlate their printability into a hollow slump cone with rheological measurements, including (1) a shear rate up-ramp followed by (2) a down-ramp in the shear rate, (3) creep tests, and (4) large-amplitude oscillatory shear (LAOS) with increasing amplitude. The PDMS-fumed silica mixtures fail to print even at the highest fumed silica loading used (9 wt. %), while LSR-PEG with 4 or 6 wt. % PEG prints well, and one of the two RTV silicone components is printable, as is the mixture due in part to its rapid chemical curing. The large differences in printability of these materials do not correlate well with any single rheological test. They do correlate with a combination of a measure of material strength, given by either the yield stress σycr from creep tests or the “flow stress” σf at which G′ and G″ cross-over in LAOS, and of material recoverability given by the dynamic yield stress σy− in test 2. The latter is measured during a down-ramp in the shear rate after reaching a maximum shear rate of 1000 s−1, the highest shear rate in the print nozzle.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43588654","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rheological properties of poly(ethylene oxide) containing graphene nanoplatelets (GNPs) having different specific surface areas (SSAs) are studied using steady shear and small amplitude oscillatory shear experiments. A series of GNPs having SSAs ranging from 175 ± 5 to 430 ± 13 m2/g was prepared using a thermomechanical exfoliation process. The complex viscosity, moduli, and yield stress of the composites increase with SSA, whereas electrical and rheological percolation threshold concentrations decrease, suggesting that higher SSAs promote filler network formation. Modeling of small amplitude oscillatory shear data using a two-phase model confirms that hydrodynamic effects dominate at low concentrations below 8 wt. %, where the particles are noninteracting. At higher concentrations, the response is dominated by filler-phase contributions. We demonstrate that the two-phase model parameters can be used to track the exfoliation of graphite into GNPs. Fitting of rheological percolation curves using Utracki and Lyngaae–Jørgensen models at low concentrations (noninteracting regime) resulted in aspect ratios between 19 and 76. At high concentrations (interacting particles), the aspect ratios determined by the Krieger–Daugherty model ranged between 5 and 24 due to aggregation. The highest aspect ratios (defined as the ratio of major dimension to minor dimension) were associated with GNPs that had the highest SSA of 430 m2/g. Strain sweeps revealed that the critical strain for the onset of nonlinear viscoelasticity scaled with SSA above the percolation threshold. The scaling relationships of the critical strain and storage modulus with volume fraction were used to infer the fractal dimensions of filler networks.
{"title":"Effect of specific surface area on the rheological properties of graphene nanoplatelet/poly(ethylene oxide) composites","authors":"Haritha Haridas, M. Kontopoulou","doi":"10.1122/8.0000531","DOIUrl":"https://doi.org/10.1122/8.0000531","url":null,"abstract":"The rheological properties of poly(ethylene oxide) containing graphene nanoplatelets (GNPs) having different specific surface areas (SSAs) are studied using steady shear and small amplitude oscillatory shear experiments. A series of GNPs having SSAs ranging from 175 ± 5 to 430 ± 13 m2/g was prepared using a thermomechanical exfoliation process. The complex viscosity, moduli, and yield stress of the composites increase with SSA, whereas electrical and rheological percolation threshold concentrations decrease, suggesting that higher SSAs promote filler network formation. Modeling of small amplitude oscillatory shear data using a two-phase model confirms that hydrodynamic effects dominate at low concentrations below 8 wt. %, where the particles are noninteracting. At higher concentrations, the response is dominated by filler-phase contributions. We demonstrate that the two-phase model parameters can be used to track the exfoliation of graphite into GNPs. Fitting of rheological percolation curves using Utracki and Lyngaae–Jørgensen models at low concentrations (noninteracting regime) resulted in aspect ratios between 19 and 76. At high concentrations (interacting particles), the aspect ratios determined by the Krieger–Daugherty model ranged between 5 and 24 due to aggregation. The highest aspect ratios (defined as the ratio of major dimension to minor dimension) were associated with GNPs that had the highest SSA of 430 m2/g. Strain sweeps revealed that the critical strain for the onset of nonlinear viscoelasticity scaled with SSA above the percolation threshold. The scaling relationships of the critical strain and storage modulus with volume fraction were used to infer the fractal dimensions of filler networks.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47432831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rheology of suspensions of rings (tori) rotating in an unbounded low Reynolds number simple shear flow is calculated using numerical simulations at dilute particle number densities [Formula: see text]. Suspensions of non-Brownian rings are studied by computing pair interactions that include hydrodynamic interactions modeled using slender body theory and particle collisions modeled using a short-range repulsive force. Particle contact and hydrodynamic interactions were found to have comparable influences on the steady-state Jeffery orbit distribution. The average tilt of the ring away from the flow-vorticity plane increased during pairwise interactions compared to the tilt associated with Jeffery rotation and the steady-state orbit distribution. Particle stresses associated with the increased tilt during the interaction were found to be comparable to the stresses induced directly by particle contact forces and the hydrodynamic velocity disturbances of other particles. The hydrodynamic diffusivity coefficients in the gradient and vorticity directions were also obtained and were found to be two orders of magnitude larger than the corresponding values in fiber suspensions at the same particle concentrations. Rotary Brownian dynamics simulations of isolated Brownian rings were used to understand the shear rate dependence of suspension rheology. The orbit distribution observed in the regime of weak Brownian motion, [Formula: see text], was surprisingly similar to that obtained from pairwise interaction calculations of non-Brownian rings. Here, the Peclet number [Formula: see text] is the ratio of the shear rate and the rotary diffusivity of the particle and [Formula: see text] is the effective inverse-aspect ratio of the particle (approximately equal to [Formula: see text] times the inverse of its non-dimensional Jeffery time period). Thus, the rheology results obtained from pairwise interactions should retain accuracy even for weakly Brownian rings [Formula: see text].
{"title":"Shear rheology of a dilute suspension of thin rings","authors":"Neeraj S. Borker, D. Koch","doi":"10.1122/8.0000628","DOIUrl":"https://doi.org/10.1122/8.0000628","url":null,"abstract":"The rheology of suspensions of rings (tori) rotating in an unbounded low Reynolds number simple shear flow is calculated using numerical simulations at dilute particle number densities [Formula: see text]. Suspensions of non-Brownian rings are studied by computing pair interactions that include hydrodynamic interactions modeled using slender body theory and particle collisions modeled using a short-range repulsive force. Particle contact and hydrodynamic interactions were found to have comparable influences on the steady-state Jeffery orbit distribution. The average tilt of the ring away from the flow-vorticity plane increased during pairwise interactions compared to the tilt associated with Jeffery rotation and the steady-state orbit distribution. Particle stresses associated with the increased tilt during the interaction were found to be comparable to the stresses induced directly by particle contact forces and the hydrodynamic velocity disturbances of other particles. The hydrodynamic diffusivity coefficients in the gradient and vorticity directions were also obtained and were found to be two orders of magnitude larger than the corresponding values in fiber suspensions at the same particle concentrations. Rotary Brownian dynamics simulations of isolated Brownian rings were used to understand the shear rate dependence of suspension rheology. The orbit distribution observed in the regime of weak Brownian motion, [Formula: see text], was surprisingly similar to that obtained from pairwise interaction calculations of non-Brownian rings. Here, the Peclet number [Formula: see text] is the ratio of the shear rate and the rotary diffusivity of the particle and [Formula: see text] is the effective inverse-aspect ratio of the particle (approximately equal to [Formula: see text] times the inverse of its non-dimensional Jeffery time period). Thus, the rheology results obtained from pairwise interactions should retain accuracy even for weakly Brownian rings [Formula: see text].","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47676407","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Negahban, Wenlong Li, J. Saiter, L. Delbreilh, K. Strabala, Z. Li
We follow the assumption that the dilatational response of glassy polymers can be characterized by a back-stress type analog that includes a thermal expansion for each elastic component and with a viscosity that is dependent on the expansion of the elastic back-stress component. To this, we add the assumption of an unloaded equilibrium temperature that correlates to the past processing through the viscous flow. After setting this in a thermodynamically consistent structure, elastic, elastic back-stress, thermal expansion, back-stress thermal expansion, heat capacity, and viscous damping are evaluated using existing experiments for the response of polycarbonate over the glassy and rubbery ranges. For the demonstration, this is done entirely using a WLF shift factor that is augmented to include, in addition, back strain superposition. We then examine the resulting model under different thermal and mechanical loadings that have the material passing through the glass transition.
{"title":"Traversing with quantitative fidelity through the glass transition of amorphous polymers: Modeling the thermodynamic dilatational flow of polycarbonate","authors":"M. Negahban, Wenlong Li, J. Saiter, L. Delbreilh, K. Strabala, Z. Li","doi":"10.1122/8.0000607","DOIUrl":"https://doi.org/10.1122/8.0000607","url":null,"abstract":"We follow the assumption that the dilatational response of glassy polymers can be characterized by a back-stress type analog that includes a thermal expansion for each elastic component and with a viscosity that is dependent on the expansion of the elastic back-stress component. To this, we add the assumption of an unloaded equilibrium temperature that correlates to the past processing through the viscous flow. After setting this in a thermodynamically consistent structure, elastic, elastic back-stress, thermal expansion, back-stress thermal expansion, heat capacity, and viscous damping are evaluated using existing experiments for the response of polycarbonate over the glassy and rubbery ranges. For the demonstration, this is done entirely using a WLF shift factor that is augmented to include, in addition, back strain superposition. We then examine the resulting model under different thermal and mechanical loadings that have the material passing through the glass transition.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43806033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stamatina Mitrou, S. Migliozzi, P. Angeli, L. Mazzei
In this work, we examine the steady shear rheology of semidilute polydisperse bubble suspensions to elucidate the role of polydispersity on the viscosity of these systems. We prove theoretically that the effect of polydispersity on suspension viscosity becomes apparent only if the bubble size distribution is bimodal, with very small and very large bubbles having similar volume fractions. In any other case, we can consider the polydisperse suspension as monodisperse, with the average bubble diameter equal to the De Brouckere mean diameter ([Formula: see text]). To confirm the theoretical results, we carried out steady shear rheological tests. Our measurements revealed an unexpected double power-law decay of the suspension relative viscosity at average capillary numbers between 0.01 and 1. To investigate this behavior further, we visualized the produced bubble suspensions under shear. The visualization experiments revealed that bubbles started forming clusters and threads at an average capillary number around 0.01, where we observed the first decay of viscosity. Clustering and alignment have been associated with shear-thinning behavior in particle suspensions. We believe that the same holds for bubble suspensions, where bubble clusters and threads align with the imposed shear flow, reducing the streamline distortions and, in turn, resulting in a decrease in the suspension viscosity. Consequently, we can attribute the first decay of the relative viscosity to the formation of bubble clusters and threads, proving that the novel shear-thinning behavior we observed is due to a combination of bubble clustering and deformation.
{"title":"Effect of polydispersity and bubble clustering on the steady shear viscosity of semidilute bubble suspensions in Newtonian media","authors":"Stamatina Mitrou, S. Migliozzi, P. Angeli, L. Mazzei","doi":"10.1122/8.0000585","DOIUrl":"https://doi.org/10.1122/8.0000585","url":null,"abstract":"In this work, we examine the steady shear rheology of semidilute polydisperse bubble suspensions to elucidate the role of polydispersity on the viscosity of these systems. We prove theoretically that the effect of polydispersity on suspension viscosity becomes apparent only if the bubble size distribution is bimodal, with very small and very large bubbles having similar volume fractions. In any other case, we can consider the polydisperse suspension as monodisperse, with the average bubble diameter equal to the De Brouckere mean diameter ([Formula: see text]). To confirm the theoretical results, we carried out steady shear rheological tests. Our measurements revealed an unexpected double power-law decay of the suspension relative viscosity at average capillary numbers between 0.01 and 1. To investigate this behavior further, we visualized the produced bubble suspensions under shear. The visualization experiments revealed that bubbles started forming clusters and threads at an average capillary number around 0.01, where we observed the first decay of viscosity. Clustering and alignment have been associated with shear-thinning behavior in particle suspensions. We believe that the same holds for bubble suspensions, where bubble clusters and threads align with the imposed shear flow, reducing the streamline distortions and, in turn, resulting in a decrease in the suspension viscosity. Consequently, we can attribute the first decay of the relative viscosity to the formation of bubble clusters and threads, proving that the novel shear-thinning behavior we observed is due to a combination of bubble clustering and deformation.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41493248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hyota Hozumi, Yuki Nohara, Yoshiki Horikawa, T. Shikata
A systematic study was performed on the dynamic viscoelastic properties of N-methylpyrrolidone (NMP) solutions of poly(vinylidene fluoride) (PVDF) samples with a wide range of weight average molar masses ( Mw) from 140 to 3300 kg mol−1 over a temperature range of −24 to 35 °C in the dilute to semidilute concentration ( c) regime in this study. In previous studies under extremely dilute conditions, it was confirmed that PVDF molecules behave as isolated highly elongated rigid rods, and the average particle length (⟨ L⟩) and diameter (⟨ d⟩) for different PVDF samples were precisely determined. The fundamental viscoelastic parameters used to analyze the dynamics of PVDF molecules dissolved in NMP were precisely determined, including the zero-shear shear viscosity ( η0), the steady state compliance ( Je), the average relaxation time ( τw), and the activation energy ( E*v) of τw in this study. E*v increased stepwise above c values corresponding to the reciprocal of the intrinsic viscosity ([ η]−1) for different solutions, independent of Mw, showing that contact or the formation of entanglements between PVDF molecules causes the increase in E*v. Je−1 was found to be proportional to the number density of PVDF molecules (ν = cNA Mw−1, where NA denotes the Avogadro constant) over the entire investigated v range, irrespective of Mw and the presence of entanglements between PVDF molecules. The reduced specific viscosities, ηsp NA⟨ L⟩3( Mw[ η])−1, were reasonably described as a universal function in the parameter ν⟨ L⟩3 over the entire investigated range, and ηsp NA⟨ L⟩3( Mw[ η])−1 ∝ ( ν⟨ L⟩3)3 was found over the region 102 < ν⟨ L⟩3 < 103, irrespective of Mw.
{"title":"Rigid rod particle like viscoelastic responses of poly(vinylidene fluoride) in N-methylpyrrolidone solution","authors":"Hyota Hozumi, Yuki Nohara, Yoshiki Horikawa, T. Shikata","doi":"10.1122/8.0000610","DOIUrl":"https://doi.org/10.1122/8.0000610","url":null,"abstract":"A systematic study was performed on the dynamic viscoelastic properties of N-methylpyrrolidone (NMP) solutions of poly(vinylidene fluoride) (PVDF) samples with a wide range of weight average molar masses ( Mw) from 140 to 3300 kg mol−1 over a temperature range of −24 to 35 °C in the dilute to semidilute concentration ( c) regime in this study. In previous studies under extremely dilute conditions, it was confirmed that PVDF molecules behave as isolated highly elongated rigid rods, and the average particle length (⟨ L⟩) and diameter (⟨ d⟩) for different PVDF samples were precisely determined. The fundamental viscoelastic parameters used to analyze the dynamics of PVDF molecules dissolved in NMP were precisely determined, including the zero-shear shear viscosity ( η0), the steady state compliance ( Je), the average relaxation time ( τw), and the activation energy ( E*v) of τw in this study. E*v increased stepwise above c values corresponding to the reciprocal of the intrinsic viscosity ([ η]−1) for different solutions, independent of Mw, showing that contact or the formation of entanglements between PVDF molecules causes the increase in E*v. Je−1 was found to be proportional to the number density of PVDF molecules (ν = cNA Mw−1, where NA denotes the Avogadro constant) over the entire investigated v range, irrespective of Mw and the presence of entanglements between PVDF molecules. The reduced specific viscosities, ηsp NA⟨ L⟩3( Mw[ η])−1, were reasonably described as a universal function in the parameter ν⟨ L⟩3 over the entire investigated range, and ηsp NA⟨ L⟩3( Mw[ η])−1 ∝ ( ν⟨ L⟩3)3 was found over the region 102 < ν⟨ L⟩3 < 103, irrespective of Mw.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46638262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Owen Watts Moore, T. Waigh, Cesar Mendoza, A. Kowalski
Lamellar gel networks based on mixtures of cetostearyl alcohol and a cationic surfactant, cetyl-trimethylammonium chloride, were studied using a combination of rheometry and optical coherence tomography (OCT) velocimetry. Experiments were conducted in a stress-controlled rheometer with a parallel plate geometry. Each formulation was found to exhibit a yield stress and thixotropy. The shear start-up behavior in response to a constant stress was directly observed using OCT velocimetry. Close to the yield stress, the velocity had a power law behavior with time after an initial period of transience. At larger stresses, the velocity undergoes two successive increases in power law scaling with time. When sheared at low, constant, shear rates 1–5 s−1, the fluids exhibit plug flow with strong wall slip at both rheometer plates. At rates of 10–150 s−1, the fluids separate into a distinctive three shear band morphology while the wall slip reduces. These rheological properties can be explained by a multilamellar vesicle to planar lamellae transition.
{"title":"Characterizing the rheology of lamellar gel networks with optical coherence tomography velocimetry","authors":"Owen Watts Moore, T. Waigh, Cesar Mendoza, A. Kowalski","doi":"10.1122/8.0000599","DOIUrl":"https://doi.org/10.1122/8.0000599","url":null,"abstract":"Lamellar gel networks based on mixtures of cetostearyl alcohol and a cationic surfactant, cetyl-trimethylammonium chloride, were studied using a combination of rheometry and optical coherence tomography (OCT) velocimetry. Experiments were conducted in a stress-controlled rheometer with a parallel plate geometry. Each formulation was found to exhibit a yield stress and thixotropy. The shear start-up behavior in response to a constant stress was directly observed using OCT velocimetry. Close to the yield stress, the velocity had a power law behavior with time after an initial period of transience. At larger stresses, the velocity undergoes two successive increases in power law scaling with time. When sheared at low, constant, shear rates 1–5 s−1, the fluids exhibit plug flow with strong wall slip at both rheometer plates. At rates of 10–150 s−1, the fluids separate into a distinctive three shear band morphology while the wall slip reduces. These rheological properties can be explained by a multilamellar vesicle to planar lamellae transition.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43506589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Armstrong, Andre Pincot, S. Jariwala, Jeffrey S. Horner, Norman Wagner, A. Beris
{"title":"Erratum: “Tensorial formulations for improved thixotropic\u0000 viscoelastic modeling of human blood” [J. Rheol. 66, 327 (2022)]","authors":"M. Armstrong, Andre Pincot, S. Jariwala, Jeffrey S. Horner, Norman Wagner, A. Beris","doi":"10.1122/8.0000662","DOIUrl":"https://doi.org/10.1122/8.0000662","url":null,"abstract":"","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42463384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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