Characterization of Complex Fluids at Very Low Frequency: Experimental Verification of the Strain Rate-Frequency Superposition (SRFS) Method
Strain rate frequency superposition (SRFS) has been suggested as new method to extend the frequency range for assessment of the complex storage modulus G* of soft glassy materials to lower frequencies. The basic idea is that relaxation processes in such fluids are accelerated by an external shear fi...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
De Gruyter
2010-10-01
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| Series: | Applied Rheology |
| Subjects: | |
| Online Access: | https://doi.org/10.3933/applrheol-20-52340 |
| _version_ | 1818677676987121664 |
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| author | Kowalczyk A. Hochstein B. Stähle P. Willenbacher N. |
| author_facet | Kowalczyk A. Hochstein B. Stähle P. Willenbacher N. |
| author_sort | Kowalczyk A. |
| collection | DOAJ |
| description | Strain rate frequency superposition (SRFS) has been suggested as new method to extend the frequency range for assessment of the complex storage modulus G* of soft glassy materials to lower frequencies. The basic idea is that relaxation processes in such fluids are accelerated by an external shear field, analogous to the effect of a temperature shift in polymer melts and solutions. Master curves for G’ and G’’ are constructed from the apparent modulus data determined from non-linear oscillatory shear experiments. Here we validate the SRFS principle for the first time by independent experiments and also demonstrate its limitations. We compare SRFS results to directly measured G’, G’’ at frequencies down to 10-3 rad/s and creep experiments lasting up to 104 s for a variety of gel-like fluids, including polymeric thickener solutions, a highly concentrated w/o-emulsion, and worm-like micellar surfactant solutions, as well as a weakly viscoelastic non-Brownian suspension of glass beads. Good agreement between SRFS data and directly measured G’, G’’ values for the thickener solutions, the emulsion as well as the suspension. Apparent viscosity data obtained from creep experiments and absolute values of the complex viscosity in the low frequency limit agree fairly well for these fluids. But the method fails for the worm-like micellar solutions and this could be due to non-uniform flow or due to flow-induced structural changes. Finally, we demonstrate that the combination of SRFS, rotational rheometry, and advanced high frequency rheology methods allows for a broad bandwidth characterization of complex fluids spanning an unprecedented frequency range of about eleven decades. |
| first_indexed | 2024-12-17T09:03:10Z |
| format | Article |
| id | doaj.art-f4c497e146734bc39230ccaaef9d4ef4 |
| institution | Directory Open Access Journal |
| issn | 1617-8106 |
| language | English |
| last_indexed | 2024-12-17T09:03:10Z |
| publishDate | 2010-10-01 |
| publisher | De Gruyter |
| record_format | Article |
| series | Applied Rheology |
| spelling | doaj.art-f4c497e146734bc39230ccaaef9d4ef42022-12-21T21:55:38ZengDe GruyterApplied Rheology1617-81062010-10-0120510.3933/applrheol-20-52340Characterization of Complex Fluids at Very Low Frequency: Experimental Verification of the Strain Rate-Frequency Superposition (SRFS) MethodKowalczyk A.0Hochstein B.1Stähle P.2Willenbacher N.3Institute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT), 76131Karlsruhe, GermanyInstitute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT), 76131Karlsruhe, GermanyInstitute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT), 76131Karlsruhe, GermanyInstitute for Mechanical Process Engineering and Mechanics, Karlsruhe Institute of Technology (KIT), 76131Karlsruhe, GermanyStrain rate frequency superposition (SRFS) has been suggested as new method to extend the frequency range for assessment of the complex storage modulus G* of soft glassy materials to lower frequencies. The basic idea is that relaxation processes in such fluids are accelerated by an external shear field, analogous to the effect of a temperature shift in polymer melts and solutions. Master curves for G’ and G’’ are constructed from the apparent modulus data determined from non-linear oscillatory shear experiments. Here we validate the SRFS principle for the first time by independent experiments and also demonstrate its limitations. We compare SRFS results to directly measured G’, G’’ at frequencies down to 10-3 rad/s and creep experiments lasting up to 104 s for a variety of gel-like fluids, including polymeric thickener solutions, a highly concentrated w/o-emulsion, and worm-like micellar surfactant solutions, as well as a weakly viscoelastic non-Brownian suspension of glass beads. Good agreement between SRFS data and directly measured G’, G’’ values for the thickener solutions, the emulsion as well as the suspension. Apparent viscosity data obtained from creep experiments and absolute values of the complex viscosity in the low frequency limit agree fairly well for these fluids. But the method fails for the worm-like micellar solutions and this could be due to non-uniform flow or due to flow-induced structural changes. Finally, we demonstrate that the combination of SRFS, rotational rheometry, and advanced high frequency rheology methods allows for a broad bandwidth characterization of complex fluids spanning an unprecedented frequency range of about eleven decades.https://doi.org/10.3933/applrheol-20-52340srfscomplex fluidshigh frequency rheologycreep experimentsnon-linear viscoelasticity |
| spellingShingle | Kowalczyk A. Hochstein B. Stähle P. Willenbacher N. Characterization of Complex Fluids at Very Low Frequency: Experimental Verification of the Strain Rate-Frequency Superposition (SRFS) Method Applied Rheology srfs complex fluids high frequency rheology creep experiments non-linear viscoelasticity |
| title | Characterization of Complex Fluids at Very Low Frequency: Experimental Verification of the Strain Rate-Frequency Superposition (SRFS) Method |
| title_full | Characterization of Complex Fluids at Very Low Frequency: Experimental Verification of the Strain Rate-Frequency Superposition (SRFS) Method |
| title_fullStr | Characterization of Complex Fluids at Very Low Frequency: Experimental Verification of the Strain Rate-Frequency Superposition (SRFS) Method |
| title_full_unstemmed | Characterization of Complex Fluids at Very Low Frequency: Experimental Verification of the Strain Rate-Frequency Superposition (SRFS) Method |
| title_short | Characterization of Complex Fluids at Very Low Frequency: Experimental Verification of the Strain Rate-Frequency Superposition (SRFS) Method |
| title_sort | characterization of complex fluids at very low frequency experimental verification of the strain rate frequency superposition srfs method |
| topic | srfs complex fluids high frequency rheology creep experiments non-linear viscoelasticity |
| url | https://doi.org/10.3933/applrheol-20-52340 |
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