Sylvain Fournier, Jérôme Chevalier, Saray Pérez-Robles, C. Carotenuto, M. Minale, H. Reveron, G. Baeza
We study the shear rheological behavior of a commercial stereolithography paste containing ≈50 vol. % of zirconia particles (diameter ≈ 100 nm) with the aim to clarify physical mechanisms occurring during the “scraping” step of this yield stress fluid. Beyond a flow curve characterized by a high zero-shear viscosity accompanied with an overall shear-thinning behavior, we investigate in a systematic way the transient regime through start-up experiments. We demonstrate that a structural transition occurs between 10−2 and 10−1 s−1, resulting in an apparent interruption of the shear-thinning. The corresponding transient response presents a pronounced extra-growth of the shear stress before to stabilize at high strain amplitude and a negative first normal stress difference peak, both effects become stronger at higher shear rates. These observations are rationalized based on the high interparticle friction owing to the polyhedral shape and the roughness of the particles. In addition, relaxation tests following the start-up experiments reveal that the samples submitted to shear rates higher than 10−1 s−1 cannot relax the shear stress to the same level as in low shear rate experiments, suggesting a durable structural modification likely to impact the quality of the parts prior to their debinding and densification. Finally, we utilize orthogonal superposition rheology to illustrate how the application of an oscillatory deformation during the scraping procedure could help to reduce the shear-thinning interruption and improve the stereolithography processing as already observed empirically during scraping.
{"title":"Spreading ceramic stereolithography pastes: Insights from shear- and orthogonal-rheology","authors":"Sylvain Fournier, Jérôme Chevalier, Saray Pérez-Robles, C. Carotenuto, M. Minale, H. Reveron, G. Baeza","doi":"10.1122/8.0000688","DOIUrl":"https://doi.org/10.1122/8.0000688","url":null,"abstract":"We study the shear rheological behavior of a commercial stereolithography paste containing ≈50 vol. % of zirconia particles (diameter ≈ 100 nm) with the aim to clarify physical mechanisms occurring during the “scraping” step of this yield stress fluid. Beyond a flow curve characterized by a high zero-shear viscosity accompanied with an overall shear-thinning behavior, we investigate in a systematic way the transient regime through start-up experiments. We demonstrate that a structural transition occurs between 10−2 and 10−1 s−1, resulting in an apparent interruption of the shear-thinning. The corresponding transient response presents a pronounced extra-growth of the shear stress before to stabilize at high strain amplitude and a negative first normal stress difference peak, both effects become stronger at higher shear rates. These observations are rationalized based on the high interparticle friction owing to the polyhedral shape and the roughness of the particles. In addition, relaxation tests following the start-up experiments reveal that the samples submitted to shear rates higher than 10−1 s−1 cannot relax the shear stress to the same level as in low shear rate experiments, suggesting a durable structural modification likely to impact the quality of the parts prior to their debinding and densification. Finally, we utilize orthogonal superposition rheology to illustrate how the application of an oscillatory deformation during the scraping procedure could help to reduce the shear-thinning interruption and improve the stereolithography processing as already observed empirically during scraping.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"12 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138949235","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}
We report on shear-stress relaxation of melts of poly(propyleneimine) (PPI) dendrimers of different generations (G2–G5). The aim of this study was to confirm our previous conclusion in Sheveleva et al. [Phys. Chem. Chem. Phys. 24, 13049–13056 (2022)] for carbosilane dendrimers that an impenetrable inner region leads to the manifestation of the crowded environment effect. The systems of PPI dendrimer melts are studied using atomistic molecular dynamics simulations. The time and frequency dependencies of the dynamic shear-stress modulus are investigated. The results are in good agreement with the available rheological experimental data for G2–G4 PPI. We have found that the crowded environment effect does not manifest itself in the mechanical relaxation of G4 PPI dendrimers in contrast to G4 carbosilane dendrimers. Despite their similar topology and close sizes, G4 PPI does not form an impenetrable core. The G5 PPI dendrimer has an impenetrable inner region, and the crowded environment effect is observed. As in carbosilane dendrimers, the maximal time of mechanical relaxation is increased due to the crowded environment effect. However, the opposite situation is for the rotational diffusion of the G5 PPI dendrimers. In contrast to carbosilane dendrimers, the rotational mobility of G5 PPI significantly slows down even taking into account the increase in the dendrimer size. The hydrogen bonding between PPI dendrimers affects the mechanical relaxation at high frequencies (short times) and enhances with growing G.
我们报告了不同世代（G2-G5）的聚（丙烯酰亚胺）（PPI）树枝状聚合物熔体的剪应力松弛。这项研究的目的是证实我们之前在 Sheveleva 等人的文章[Phys. Chem. Chem. Phys. 24, 13049-13056 (2022)]中针对碳硅烷树枝状聚合物得出的结论，即无法穿透的内部区域会导致拥挤环境效应的显现。我们利用原子分子动力学模拟研究了 PPI 树枝状聚合物熔体系统。研究了动态剪应力模量的时间和频率依赖性。研究结果与 G2-G4 PPI 的现有流变实验数据十分吻合。我们发现，与 G4 碳硅烷树枝状聚合物相比，拥挤环境效应在 G4 PPI 树枝状聚合物的机械松弛中并不明显。尽管拓扑结构相似且尺寸接近，但 G4 PPI 并未形成不可穿透的核心。G5 PPI 树枝状聚合物有一个无法穿透的内部区域，并观察到拥挤环境效应。与碳硅烷树枝状聚合物一样，由于拥挤环境效应，机械松弛的最长时间延长了。然而，G5 PPI 树枝状聚合物的旋转扩散情况恰恰相反。与碳硅烷树枝状聚合物相比，即使考虑到树枝状聚合物尺寸的增加，G5 PPI 的旋转流动性也会明显减慢。PPI 树枝状聚合物之间的氢键影响了高频率（短时间）的机械松弛，并随着 G 值的增加而增强。
{"title":"Molecular dynamics simulation of mechanical relaxation of poly(propyleneimine) dendrimers","authors":"N. Sheveleva, A. Komolkin, D. Markelov","doi":"10.1122/8.0000723","DOIUrl":"https://doi.org/10.1122/8.0000723","url":null,"abstract":"We report on shear-stress relaxation of melts of poly(propyleneimine) (PPI) dendrimers of different generations (G2–G5). The aim of this study was to confirm our previous conclusion in Sheveleva et al. [Phys. Chem. Chem. Phys. 24, 13049–13056 (2022)] for carbosilane dendrimers that an impenetrable inner region leads to the manifestation of the crowded environment effect. The systems of PPI dendrimer melts are studied using atomistic molecular dynamics simulations. The time and frequency dependencies of the dynamic shear-stress modulus are investigated. The results are in good agreement with the available rheological experimental data for G2–G4 PPI. We have found that the crowded environment effect does not manifest itself in the mechanical relaxation of G4 PPI dendrimers in contrast to G4 carbosilane dendrimers. Despite their similar topology and close sizes, G4 PPI does not form an impenetrable core. The G5 PPI dendrimer has an impenetrable inner region, and the crowded environment effect is observed. As in carbosilane dendrimers, the maximal time of mechanical relaxation is increased due to the crowded environment effect. However, the opposite situation is for the rotational diffusion of the G5 PPI dendrimers. In contrast to carbosilane dendrimers, the rotational mobility of G5 PPI significantly slows down even taking into account the increase in the dendrimer size. The hydrogen bonding between PPI dendrimers affects the mechanical relaxation at high frequencies (short times) and enhances with growing G.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"78 5","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138957830","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}
Shear-induced crystallization behavior was studied using a phase-separated blend comprising a polypropylene continuous phase and a low-density polyethylene (LDPE) dispersion, which is known to show strain hardening in transient elongation viscosity. In this study, crystallization behavior was mainly evaluated by the light intensity transmitted through a transparent parallel-plate geometry. It was found that shear-induced crystallization was greatly accelerated by the addition of LDPE, resulting in a high crystallization temperature and a highly oriented structure. When the sample was cooled slowly, however, shear-induced crystallization was not accelerated by LDPE. Furthermore, extrusion was performed using a capillary rheometer. The molecular orientation in the strands collected after cooling in the air was found to be enhanced by the LDPE addition, suggesting that flow-induced crystallization was accelerated even at capillary extrusion.
{"title":"Shear-induced crystallization of polypropylene/low-density polyethylene blend","authors":"Khunanya Janchai, Masayuki Yamaguchi","doi":"10.1122/8.0000742","DOIUrl":"https://doi.org/10.1122/8.0000742","url":null,"abstract":"Shear-induced crystallization behavior was studied using a phase-separated blend comprising a polypropylene continuous phase and a low-density polyethylene (LDPE) dispersion, which is known to show strain hardening in transient elongation viscosity. In this study, crystallization behavior was mainly evaluated by the light intensity transmitted through a transparent parallel-plate geometry. It was found that shear-induced crystallization was greatly accelerated by the addition of LDPE, resulting in a high crystallization temperature and a highly oriented structure. When the sample was cooled slowly, however, shear-induced crystallization was not accelerated by LDPE. Furthermore, extrusion was performed using a capillary rheometer. The molecular orientation in the strands collected after cooling in the air was found to be enhanced by the LDPE addition, suggesting that flow-induced crystallization was accelerated even at capillary extrusion.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":" 6","pages":""},"PeriodicalIF":3.3,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138994940","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}
Pub Date : 2023-12-01Epub Date: 2023-11-30DOI: 10.1089/env.2022.0053
Lariah Edwards, Lubna Ahmed, Leslie Martinez, Sophia Huda, Bhavna Shamasunder, Jasmine A McDonald, Robert Dubrow, Beaumont Morton, Ami R Zota
The disproportionate use of chemical straighteners and skin lighteners by women of color is a growing public health concern given the link between product use and adverse health effects. Prior studies examined product use as an individual choice but neglected social-structural factors, which influence beauty perceptions and personal decisions around product use. We used a community-based participatory research approach to characterize product use by demographics and investigated how racialized beauty norms impact use among 297 women and femme-identifying individuals in Northern Manhattan and the South Bronx. Product use varied by race/ethnicity, nativity, and messaging from family and peers. Black respondents were more likely to ever use chemical straighteners than non-Black respondents (OR = 2.0; 95% CI = 1.2-3.2), as were respondents who heard that family members express a preference for straight hair compared with respondents whose family members expressed mixed preferences about hairstyles (OR = 2.0; 95% CI = 1.1-3.7). Compared with non-Asian respondents and respondents born in the United States, Asian respondents and respondents born in other countries, respectively, had threefold higher odds of ever using skin lighteners (Asian: OR = 3.2; 95% CI = 1.4-7.0; born in other countries: OR = 3.4; 95% CI = 1.9-6.1). Respondents' perceptions that others believe straight hair or lighter skin confer benefits such as beauty, professionalism, or youth were associated with greater use of chemical straighteners and skin lighteners. These findings highlight the pervasiveness of racialized beauty norms and point to the need to reduce the demand for and sale of these products through community education, market-based strategies, and public policy.
鉴于产品使用与不良健康影响之间的联系，有色人种女性过多使用化学直发器和皮肤美白剂日益成为一个公共健康问题。之前的研究将产品的使用视为个人选择，但忽略了社会结构因素，而这些因素会影响人们对美的看法和个人对产品使用的决定。我们采用了一种基于社区的参与式研究方法，按人口统计学特征来描述产品的使用情况，并调查了种族化的美容规范如何影响曼哈顿北部和南布朗克斯区 297 名女性和女性身份认同者的产品使用情况。产品使用情况因种族/民族、出生地以及来自家庭和同龄人的信息而异。黑人受访者比非黑人受访者更有可能使用化学直发器（OR = 2.0；95% CI = 1.2-3.2），听说家人喜欢直发的受访者也比家人对发型喜好不一的受访者更有可能使用化学直发器（OR = 2.0；95% CI = 1.1-3.7）。与非亚裔受访者和在美国出生的受访者相比，亚裔受访者和在其他国家出生的受访者使用过美白剂的几率分别高出三倍（亚裔：OR = 3.2；95% CI = 1.1-3.7）：OR=3.2；95% CI=1.4-7.0；在其他国家出生的受访者：OR=3.4；95% CI=1.9-6.1）。受访者认为他人认为直发或浅色皮肤会带来美丽、专业或年轻等好处与更多使用化学直发器和皮肤美白剂有关。这些发现凸显了种族化美容规范的普遍性，并指出有必要通过社区教育、市场策略和公共政策来减少对这些产品的需求和销售。
{"title":"Beauty Inside Out: Examining Beauty Product Use Among Diverse Women and Femme-Identifying Individuals in Northern Manhattan and South Bronx Through an Environmental Justice Framework.","authors":"Lariah Edwards, Lubna Ahmed, Leslie Martinez, Sophia Huda, Bhavna Shamasunder, Jasmine A McDonald, Robert Dubrow, Beaumont Morton, Ami R Zota","doi":"10.1089/env.2022.0053","DOIUrl":"10.1089/env.2022.0053","url":null,"abstract":"<p><p>The disproportionate use of chemical straighteners and skin lighteners by women of color is a growing public health concern given the link between product use and adverse health effects. Prior studies examined product use as an individual choice but neglected social-structural factors, which influence beauty perceptions and personal decisions around product use. We used a community-based participatory research approach to characterize product use by demographics and investigated how racialized beauty norms impact use among 297 women and femme-identifying individuals in Northern Manhattan and the South Bronx. Product use varied by race/ethnicity, nativity, and messaging from family and peers. Black respondents were more likely to ever use chemical straighteners than non-Black respondents (OR = 2.0; 95% CI = 1.2-3.2), as were respondents who heard that family members express a preference for straight hair compared with respondents whose family members expressed mixed preferences about hairstyles (OR = 2.0; 95% CI = 1.1-3.7). Compared with non-Asian respondents and respondents born in the United States, Asian respondents and respondents born in other countries, respectively, had threefold higher odds of ever using skin lighteners (Asian: OR = 3.2; 95% CI = 1.4-7.0; born in other countries: OR = 3.4; 95% CI = 1.9-6.1). Respondents' perceptions that others believe straight hair or lighter skin confer benefits such as beauty, professionalism, or youth were associated with greater use of chemical straighteners and skin lighteners. These findings highlight the pervasiveness of racialized beauty norms and point to the need to reduce the demand for and sale of these products through community education, market-based strategies, and public policy.</p>","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"34 1","pages":"449-460"},"PeriodicalIF":2.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10704575/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85700443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The thinning of a cylinder of a polymer solution in a volatile solvent is argued to be controlled by solvent diffusion through a dense polymer layer at the cylinder surface. This naturally leads to the exponential time dependence of cylinder radius that is observed in experiments using a fast camera, such as capillary breakup extensional rheometry (CaBER). The relaxation time is controlled by the thickness of the dense (and often glassy) polymer layer and the diffusion coefficient of solvent through that layer. If correct, this means that while CaBER is very useful for understanding fiber spinning, the relaxation time does not yield a measure of the extensional viscosity of polymer solutions in volatile solvents.
{"title":"Fiber spinning from polymer solutions","authors":"Ralph H. Colby","doi":"10.1122/8.0000726","DOIUrl":"https://doi.org/10.1122/8.0000726","url":null,"abstract":"The thinning of a cylinder of a polymer solution in a volatile solvent is argued to be controlled by solvent diffusion through a dense polymer layer at the cylinder surface. This naturally leads to the exponential time dependence of cylinder radius that is observed in experiments using a fast camera, such as capillary breakup extensional rheometry (CaBER). The relaxation time is controlled by the thickness of the dense (and often glassy) polymer layer and the diffusion coefficient of solvent through that layer. If correct, this means that while CaBER is very useful for understanding fiber spinning, the relaxation time does not yield a measure of the extensional viscosity of polymer solutions in volatile solvents.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"37 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372164","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}
José Alberto Rodríguez Agudo, Jan Haeberle, Michael Müller-Pabel, Alexander Troiss, Abhishek Shetty, Joachim Kaschta, Christopher Giehl
This study discusses the feasibility of using a combined torsional-axial rheometer to indirectly measure the complex Poisson’s ratio based on shear and Young’s modulus. For this purpose, isothermal frequency sweeps in torsion and extension are performed sequentially on the same cylindrical specimen and under the same environmental conditions. The method is tested on two amorphous polymers, a semicrystalline polymer, a polymer blend, and a copolymer. The article includes an extensive literature review and an uncertainty assessment of the method to provide a basis for subsequent data comparison with existing research. The experimental data show a monotonic increase in the complex Poisson’s ratio up to 0.5 as the temperature approaches α-relaxation for all samples, except for the amorphous polymer. The latter shows a local minimum in the complex Poisson’s ratio observed near α-relaxation, which disappears after thermal annealing of the sample above the α-relaxation temperature. The real and imaginary parts of the complex Poisson’s ratio are additionally determined by evaluating both phase shift angles from torsional and extensional measurements. All polymers show a certain offset between the torsional and extensional phase shift angles in the glassy state, which gradually decreases as the temperature approaches α-relaxation. The complex Poisson’s ratio results are in good agreement with the literature data obtained by existing methods. This confirms that the method is applicable to polymers up to α-relaxation temperatures with significant time savings due to the nondestructive approach. This is of particular interest, given the limited availability of data in the literature.
{"title":"Characterization of the temperature and frequency dependency of the complex Poisson’s ratio using a novel combined torsional-axial rheometer","authors":"José Alberto Rodríguez Agudo, Jan Haeberle, Michael Müller-Pabel, Alexander Troiss, Abhishek Shetty, Joachim Kaschta, Christopher Giehl","doi":"10.1122/8.0000675","DOIUrl":"https://doi.org/10.1122/8.0000675","url":null,"abstract":"This study discusses the feasibility of using a combined torsional-axial rheometer to indirectly measure the complex Poisson’s ratio based on shear and Young’s modulus. For this purpose, isothermal frequency sweeps in torsion and extension are performed sequentially on the same cylindrical specimen and under the same environmental conditions. The method is tested on two amorphous polymers, a semicrystalline polymer, a polymer blend, and a copolymer. The article includes an extensive literature review and an uncertainty assessment of the method to provide a basis for subsequent data comparison with existing research. The experimental data show a monotonic increase in the complex Poisson’s ratio up to 0.5 as the temperature approaches α-relaxation for all samples, except for the amorphous polymer. The latter shows a local minimum in the complex Poisson’s ratio observed near α-relaxation, which disappears after thermal annealing of the sample above the α-relaxation temperature. The real and imaginary parts of the complex Poisson’s ratio are additionally determined by evaluating both phase shift angles from torsional and extensional measurements. All polymers show a certain offset between the torsional and extensional phase shift angles in the glassy state, which gradually decreases as the temperature approaches α-relaxation. The complex Poisson’s ratio results are in good agreement with the literature data obtained by existing methods. This confirms that the method is applicable to polymers up to α-relaxation temperatures with significant time savings due to the nondestructive approach. This is of particular interest, given the limited availability of data in the literature.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"34 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135372176","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}
Thixotropy, antithixotropy, and viscoelasticity are three types of time-dependent dynamics that involve fundamentally different underlying physical processes. Here, we show that the three dynamics exhibit different signatures in hysteresis by examining the fingerprints of the simplest thixotropic kinetic model, a new antithixotropic model that we introduce here, and the Giesekus model. We start by showing that a consistent protocol to generate hysteresis loops is a discrete shear-rate controlled ramp that begins and ends at high shear rates, rather than at low shear rates. Using this protocol, we identify two distinguishing features in the resulting stress versus shear rate loops. The first is the direction of the hysteresis loops: clockwise for thixotropy, but counterclockwise for viscoelasticity and antithixotropy. A second feature is achieved at high ramping rates where all responses lose hysteresis: the viscoelastic response shows a stress plateau at low shear rates due to lack of stress relaxation, whereas the thixotropic and antithixotropic responses are purely viscous with minimal shear thinning or thickening. We establish further evidence for these signatures by experimentally measuring the hysteresis of Laponite suspensions, carbon black suspensions, and poly(ethylene oxide) solutions, each representing a historically accepted example of each class of material behavior. The signatures measured in experiments are consistent with those predicted by the three models. This study reveals different fingerprints in hysteresis loops associated with thixotropy, antithixotropy, and viscoelasticity, which may be helpful in distinguishing the three time-dependent responses.
{"title":"Thixotropy, antithixotropy, and viscoelasticity in hysteresis","authors":"Yilin Wang, Randy H. Ewoldt","doi":"10.1122/8.0000620","DOIUrl":"https://doi.org/10.1122/8.0000620","url":null,"abstract":"Thixotropy, antithixotropy, and viscoelasticity are three types of time-dependent dynamics that involve fundamentally different underlying physical processes. Here, we show that the three dynamics exhibit different signatures in hysteresis by examining the fingerprints of the simplest thixotropic kinetic model, a new antithixotropic model that we introduce here, and the Giesekus model. We start by showing that a consistent protocol to generate hysteresis loops is a discrete shear-rate controlled ramp that begins and ends at high shear rates, rather than at low shear rates. Using this protocol, we identify two distinguishing features in the resulting stress versus shear rate loops. The first is the direction of the hysteresis loops: clockwise for thixotropy, but counterclockwise for viscoelasticity and antithixotropy. A second feature is achieved at high ramping rates where all responses lose hysteresis: the viscoelastic response shows a stress plateau at low shear rates due to lack of stress relaxation, whereas the thixotropic and antithixotropic responses are purely viscous with minimal shear thinning or thickening. We establish further evidence for these signatures by experimentally measuring the hysteresis of Laponite suspensions, carbon black suspensions, and poly(ethylene oxide) solutions, each representing a historically accepted example of each class of material behavior. The signatures measured in experiments are consistent with those predicted by the three models. This study reveals different fingerprints in hysteresis loops associated with thixotropy, antithixotropy, and viscoelasticity, which may be helpful in distinguishing the three time-dependent responses.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"23 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135870142","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}
Meera Ramaswamy, Itay Griniasty, Danilo B. Liarte, Abhishek Shetty, Eleni Katifori, Emanuela Del Gado, James P. Sethna, Bulbul Chakraborty, Itai Cohen
Nearly, all dense suspensions undergo dramatic and abrupt thickening transitions in their flow behavior when sheared at high stresses. Such transitions occur when the dominant interactions between the suspended particles shift from hydrodynamic to frictional. Here, we interpret abrupt shear thickening as a precursor to a rigidity transition and give a complete theory of the viscosity in terms of a universal crossover scaling function from the frictionless jamming point to a rigidity transition associated with friction, anisotropy, and shear. Strikingly, we find experimentally that for two different systems—cornstarch in glycerol and silica spheres in glycerol—the viscosity can be collapsed onto a single universal curve over a wide range of stresses and volume fractions. The collapse reveals two separate scaling regimes due to a crossover between frictionless isotropic jamming and frictional shear jamming, with different critical exponents. The material-specific behavior due to the microscale particle interactions is incorporated into a scaling variable governing the proximity to shear jamming, that depends on both stress and volume fraction. This reformulation opens the door to importing the vast theoretical machinery developed to understand equilibrium critical phenomena to elucidate fundamental physical aspects of the shear thickening transition.
{"title":"Universal scaling of shear thickening transitions","authors":"Meera Ramaswamy, Itay Griniasty, Danilo B. Liarte, Abhishek Shetty, Eleni Katifori, Emanuela Del Gado, James P. Sethna, Bulbul Chakraborty, Itai Cohen","doi":"10.1122/8.0000697","DOIUrl":"https://doi.org/10.1122/8.0000697","url":null,"abstract":"Nearly, all dense suspensions undergo dramatic and abrupt thickening transitions in their flow behavior when sheared at high stresses. Such transitions occur when the dominant interactions between the suspended particles shift from hydrodynamic to frictional. Here, we interpret abrupt shear thickening as a precursor to a rigidity transition and give a complete theory of the viscosity in terms of a universal crossover scaling function from the frictionless jamming point to a rigidity transition associated with friction, anisotropy, and shear. Strikingly, we find experimentally that for two different systems—cornstarch in glycerol and silica spheres in glycerol—the viscosity can be collapsed onto a single universal curve over a wide range of stresses and volume fractions. The collapse reveals two separate scaling regimes due to a crossover between frictionless isotropic jamming and frictional shear jamming, with different critical exponents. The material-specific behavior due to the microscale particle interactions is incorporated into a scaling variable governing the proximity to shear jamming, that depends on both stress and volume fraction. This reformulation opens the door to importing the vast theoretical machinery developed to understand equilibrium critical phenomena to elucidate fundamental physical aspects of the shear thickening transition.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135481366","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}
Adeniyi Ogunkeye, Rebecca E. Hudson, Daniel J. Curtis
In a recent paper [Hassager, J. Rheol. 64, 545–550 (2020)], Hassager performed an analysis of the start up of stress-controlled oscillatory flow based on the general theory of linear viscoelasticity. The analysis provided a theoretical basis for exploring the establishment of a steady strain offset that is inherent to stress controlled oscillatory rheometric protocols. However, the analysis neglected the impact of instrument inertia on the establishment of the steady periodic response. The inclusion of the inertia term in the framework is important since it (i) gives rise to inertio-elastic ringing and (ii) introduces an additional phase shift in the periodic part of the response. Herein, we modify the expressions to include an appropriate inertial contribution and demonstrate that the presence of the additional terms can have a substantial impact on the time scale required to attain the steady state periodic response. The analysis is then applied to an aqueous solution of wormlike micelles.
在最近的一篇论文[Hassager, J. Rheol. 64, 545-550(2020)]中，Hassager基于一般线性粘弹性理论对应力控制振荡流的启动进行了分析。该分析为探索建立应力控制振荡流变法固有的稳定应变偏移提供了理论基础。然而，该分析忽略了仪器惯性对建立稳定周期响应的影响。在框架中包含惯性项是很重要的，因为它(i)引起了惯性弹性环，(ii)在响应的周期部分引入了额外的相移。在此，我们修改表达式以包含适当的惯性贡献，并证明附加项的存在可以对获得稳态周期响应所需的时间尺度产生实质性影响。然后将分析应用于蠕虫状胶束的水溶液。
{"title":"The effect of instrument inertia on the initiation of oscillatory flow in stress controlled rheometry","authors":"Adeniyi Ogunkeye, Rebecca E. Hudson, Daniel J. Curtis","doi":"10.1122/8.0000665","DOIUrl":"https://doi.org/10.1122/8.0000665","url":null,"abstract":"In a recent paper [Hassager, J. Rheol. 64, 545–550 (2020)], Hassager performed an analysis of the start up of stress-controlled oscillatory flow based on the general theory of linear viscoelasticity. The analysis provided a theoretical basis for exploring the establishment of a steady strain offset that is inherent to stress controlled oscillatory rheometric protocols. However, the analysis neglected the impact of instrument inertia on the establishment of the steady periodic response. The inclusion of the inertia term in the framework is important since it (i) gives rise to inertio-elastic ringing and (ii) introduces an additional phase shift in the periodic part of the response. Herein, we modify the expressions to include an appropriate inertial contribution and demonstrate that the presence of the additional terms can have a substantial impact on the time scale required to attain the steady state periodic response. The analysis is then applied to an aqueous solution of wormlike micelles.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135590984","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}
Olivier Vergote, Inge Bellemans, Amy Van den Bulck, Maksym Shevchenko, Roman Starykh, Evgueni Jak, Kim Verbeken
Heterogeneous slag viscosity measurements have a wide variety of parameters, such as particle size, shape, solid volume fraction, and shear rate, which affect the final measured viscosity. Often, some of these parameters are neglected or predicted via models, since it is experimentally difficult to determine them during high-temperature slag viscosity measurements. In this work, a viscosity apparatus was used, which allows quenching of the sample after measurement. This way, all relevant parameters could be experimentally determined. The viscosities of three datasets were studied with various spinel sizes: small (13 μm), medium (34 μm), and large particles (76 μm). Within each dataset, the composition of the liquid slag matrix was kept constant to uniquely measure the effect of solids. Shear thinning, i.e., a decreasing viscosity with increasing shear rate, was observed for all samples, even at a low vol. % of 1.8. Moreover, stronger shear thinning was observed at a higher vol. % and for smaller spinel particles. On the basis of these results, the phenomenon of shear thinning was discussed and mainly attributed to the particle–particle orientation in the suspension. The obtained viscosity values were used to optimize a Krieger–Dougherty equation, which describes the viscosity increase caused by the presence of a certain vol. % of spinel particles, with a certain size and at a specific shear rate.
{"title":"Viscosity experiments of slag-spinel suspensions: The effect of volume fraction, particle size, and shear rate","authors":"Olivier Vergote, Inge Bellemans, Amy Van den Bulck, Maksym Shevchenko, Roman Starykh, Evgueni Jak, Kim Verbeken","doi":"10.1122/8.0000690","DOIUrl":"https://doi.org/10.1122/8.0000690","url":null,"abstract":"Heterogeneous slag viscosity measurements have a wide variety of parameters, such as particle size, shape, solid volume fraction, and shear rate, which affect the final measured viscosity. Often, some of these parameters are neglected or predicted via models, since it is experimentally difficult to determine them during high-temperature slag viscosity measurements. In this work, a viscosity apparatus was used, which allows quenching of the sample after measurement. This way, all relevant parameters could be experimentally determined. The viscosities of three datasets were studied with various spinel sizes: small (13 μm), medium (34 μm), and large particles (76 μm). Within each dataset, the composition of the liquid slag matrix was kept constant to uniquely measure the effect of solids. Shear thinning, i.e., a decreasing viscosity with increasing shear rate, was observed for all samples, even at a low vol. % of 1.8. Moreover, stronger shear thinning was observed at a higher vol. % and for smaller spinel particles. On the basis of these results, the phenomenon of shear thinning was discussed and mainly attributed to the particle–particle orientation in the suspension. The obtained viscosity values were used to optimize a Krieger–Dougherty equation, which describes the viscosity increase caused by the presence of a certain vol. % of spinel particles, with a certain size and at a specific shear rate.","PeriodicalId":16991,"journal":{"name":"Journal of Rheology","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135590506","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：