Flow induced birefringence

D. S. Pearson, A. D. Kiss, L. J. Fetters, andM. Doi, Flow-induced birefringence of concentrated polyisoprene solutions, J. Rheol., 33, 517 (1989) D. S. Pearson, E. Herbolzheimer, N. Grizzuti, and G. Marrucci, Transient behavior of entangled polymers at high shear rates, J. Polym. Sci., Part B, 29,1589 (1991). 

Figure 2. Experimentally determined flow-induced birefringence vs. strain rate for atactic polystyrene. The maximum value of birefringence is 1.15 x 10, which corresponds to an optical retardation of 27 nm for a cell depth of 1.8 mm 0.1% solution. Mu, 5.5 X 10 in decahydronaphthalene).

The optical system used to assess flow-induced birefringence consisted of a 2-mW polarized He-Ne laser focused by a condenser lens on the center of the flow field. The birefringence patterns are observed between crossed polars by using a quarter wave (X/4) retardation plate as a Senarmont compensator. The polarized laser has an extinction ratio of 100 1 the polarizer and analyzer are Carl Zeiss components with extinction ratios of approximately 10... 

For e smaller than a critical value ec, the chain remains in a coiled state. As e > ec, the chain drastically extends as shown by a steeper increase in the flow-induced birefringence (Fig. 9). At the onset of CST, the corresponding critical Dec... 

Fig. 9 Schematic drawing of flow-induced birefringence as a function of strain rate during CST and chain scission. (Adopted with permission from Odell and Keller [28], Copyright 1986 John Wiley Sons)...

Hsieh CC, Park SJ, Larson RG (2005) Brownian dynamics modeling of flow-induced birefringence and chain scission in dilute polymer solutions in a planar cross-slot flow. Macromolecules 38 1456-1468... 

Fig. 5. Shear-flow induced birefringence as a function of temperature and shear-rate for an isotropic PpPTA 9% (w/w) solution in sulfuric acid...

Shear flow-induced birefringence measurements of an isotropic solution of PpPTA in concentrated sulfuric acid with a clearing point of 45 °C were also performed by Picken [77]. As shown in Fig. 5 the flow-induced birefringence increases strongly when the isotropic-nematic transition is approached. The results demonstrate that the application of a relatively small shear rate already leads to a degree of orientational order, in the initially isotropic solution, that is comparable with the order in the nematic phase. This points to a strong coupling between the orientation and the external flow field, and to the occurrence of a shear-induced phase transition. 

Lee JY, Fuller GG, Hudson NE, Yuan XF (2005) Investigation of shear-banding structure in wormlike micellar solution by point-wise flow-induced birefringence measurements. J Rheol... 

One application of birefringence related to polymer rheology is stress field visualization. It relies on flow-induced birefringence techniques to examine the spatial and temporal evolutions of stress in a polymer melt (see Fig. 9) (55). In this... 

Shyu, G. D., Isayev, A. I., and Lee, H. S., Numerical Simulation of Flow-induced Birefringence in Injection Molded Disk, Korea-Australia Rheology Journal, 15, 159-166 (2003). 

The viscous heating was taken into account using the energy dissipation function [12], The polymer density change due to temperature and pressure variations was calculated using the Tait equation [13]. The flow-induced birefringence was calculated from the normal and shear stresses using the stress-optical rule [8]. 

A viscoelastic numerical scheme was developed for calculation of the three components of the flow-induced birefringence and gas/polymer interface in GAIM. The predicted results for tubular moldings were found to be in good agreement with experimental data. 

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