The application of flow birefringence to rheological studies of polymer melts

An experimental and numerical investigation of a viscoelastic flow around a cylinder

“…Stress optic rule Flow Induced Birefringence enables measurement of extra stresses in many flowing materials, especially in polymer melts and solutions. For many polymeric materials, extensive studies [e.g., Wales ( 1976)] have shown that the refractive index tensor is related to the extra stress tensor by a simple linear relation [Fuller ( 1990)], the stress optical rule:…”

Optical Rheology of a Polydimethylsiloxane Fluid in Jeffrey-Hamel Type Flow

“…This has been found in polymer melts subjected to very high tensile stresses [18]. However, in an overwhelming majority of experiments [8,11] that are relevant to practical situations in polymer processing, stresses appear to be too small for deviation from the linear stress-optical law.…”

“…Majority of the rheo-optical studies of polymeric systems done so far involved the mechanical measurements of stress and optical measurements of birefringence to evaluate the linear stress-optical coefficient [10][11][12][13]. In this paper we illustrate the use of optical techniques (laser Doppler anemometry) measure birefringence, compute stress and then evaluate the linear stress-optical coefficient of a polydimethylsiloxane (PDMS) melt at room temperature in planar extension along the centerline of a converging wedge flow cell.…”

Numerical Analysis of Viscoelastic Start-up Flow in Channels with a Tapered Contraction

“…We used the parameters of the 2 mode Leonov model by Isayev et al [12] ( s=0.09, i1= 5.44 x 103 Pa•s, 112 = 1.50 x 103 Pa•s, B1 = 0.80 s, 92 = 0.027 s ), which are determined based on the measurement by Wales [13] . The density of the test fluid is 960 kg/m3.…”

“…The density of the test fluid is 960 kg/m3. Figure 1 shows both the measurements [13] and the predictions of the shear viscosity, r1s, and the first normal stress difference, N1, of the polystyrene melt by the Leonov model. Figure 2 shows the uniaxial elongational viscosity, 11E, predicted by the Leonov model.…”