Abstract
A setup for the optical measurement of elastic properties during the flow of complex fluids is presented. Brillouin light scattering and rotational rheology are combined in order to simultaneously measure the high-frequency longitudinal elastic modulus in a classical rheometer along with the zero-shear viscosity. Brillouin light scattering allows for the contactless determination of local elastic properties. First measurements of a diluted polymer system suggest a homogeneous orientation of polymer molecules throughout the sample as soon as a critical shear rate has been reached at one spatial position.
Highlights
When complex fluids are subject to shear flow, many different phenomena such as orientation of molecules or fillers, nucleation of crystals, shear banding etc. can occur
For a more detailed study of the influence of shearing on complex fluids, rheology has e.g. been coupled with polarizing microscopy and different small-angle scattering technologies: SALS, SAXS, SANS [2,7,8,9,10,11,12,13,14,15]
The spectra have been recorded with an acquisition time of about 4 minutes for the temperature dependent measurements shown in Fig. 11, 15 minutes for the shear rate dependent measurements (Fig. 12) and 50 seconds for the relaxation measurements (Fig. 13)
Summary
When complex fluids are subject to shear flow, many different phenomena such as orientation of molecules or fillers, nucleation of crystals, shear banding etc. can occur. For a more detailed study of the influence of shearing on complex fluids, rheology has e.g. been coupled with polarizing microscopy and different small-angle scattering technologies: SALS, SAXS, SANS [2,7,8,9,10,11,12,13,14,15]. Part of these techniques are able to deliver spatially resolved information. More sophisticated setups allowing the record of the complete stiffness tensor at hypersound frequencies during shearing of complex fluids
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