Concentric cylinders birefringence

After these theoretical considerations, it seems of interest to glance over some experimental results. Philippoff (37) investigated a 9 per cent solution of polyisobutylene (Vistanex B-100) in decalin and a 30 per cent solution of polystyrene (PX 134, Dow Chem. Corp.) in toluene. He used a conventional concentric cylinder apparatus for the flow birefringence measurements in the 1—2 plane and the parallel plate apparatus just sketched for the measurements in the 1—3 plane. For comparison, the results in the 1—2 plane are given in the form ... 

As already mentioned in Chapter 1, there are mainly three geometries suitable for the measurement of flow birefringence, viz. those of the concentric cylinder apparatus, the adapted cone-and-plate apparatus and the slit-capillary with a rectangular cross-section. The general principles of the pertinent techniques have been described in the same chapter. The purpose of the present chapter is to give details of the design and construction in order to enable the reader to form a judgement as to the efficiency of the proposed methods, i.e. the relation between information and experimental effort. 

If the present author would be asked why he did not first try to investigate the flow birefringence of polymer melts with the aid of a concentric cylinder apparatus, he could only answer because of the inconveniences experienced with such a type of an apparatus, when the viscosity of polymer melts is measured. As a matter of fact, the apparatus for polymer solutions, as described in the previous sections, would not.be suitable because of the impossibility to fill it with a polymer melt. As a consequence, a new type of apparatus had to be designed in any case. 

The decision was taken in favour of a cone-and-plate apparatus, as such a type of apparatus has proven to be very suitable for the viscometry of polymer melts. Afterwards, as a consequence of the experiences gathered with this apparatus, it is felt that also a concentric cylinder apparatus would be useful, viz. for the investigation of the flow birefringence in... 

Hydrodynamic shear Flow birefringence is usually measured in an apparatus which consists of two concentric cylinders (Figure 9.13). Two types of apparatus are available depending on whether the inner or the outer cylinder is rotated. For various reasons the outer cylinder... 

The concentric cylinder geometry was used in the first studies of flow birefringence." The shear field is inhomogeneous within the gap, and as narrow a gap as possible is needed to reduce this effect. A very small gap gives alignment difficulties and reduces the ability to view through the gap for birefringence measurements. 

The design of the apparatus is very involved, certainly more so than for the concentric cylinders. There were also difficulties with parasitic birefringences in the apparatus. ... 

Viscoelastic data of relatively high concentrated solutions were measured in oscillating and steady-shear flow at room temperature (ca. 25C) by using Fluid Spectrometers RFS-8500 and RFSn, and a Mechanical Spectrometer RMS-800 of Rheometrics, Inc., with the cone-and-plate and the co-axial cylinder. At relatively low concentrations most of 7 data was measured with capillary viscometers of Maron-Krieger-Sisko type at 2511, and J data at two low concentrations were obtained from flow birefringence measurements[12] for comparison. To examine the degradation of the samples after the measurements of viscoelastic properties, we measured [ 7 ] to confirm that there was no degradation. 

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