Band viscometer

Band viscometer used for high shear rate testing of inks and coatings. 

Other possible reasons for the discrepancy in the Mark-Houwink parameters may be due to the band spreading effects and inadequate signal-to-noise quality at the tails of the viscometer chromatogram. These subjects will be the topic of our future investigations in this area. 

Miller et al. have recently reported infra-red dichroic data obtained for high density polyethylene crystallised under the orientation and pressure effects of a pressure capillary viscometer. Their data for a number of crystalline bands (including the 1894 cm" absorption) showed that the crystal c-axes were almost perfectly oriented (f 1) in the initial extrusion direction. The amorphous orientation functions were generally lower, but corresponded to an extension ratio between 2 and 7 when compared with the above results of Read and Stein and of Glenz and Peterlin. Further evidence was also obtained for the relatively high orientation of the amorphous component of the 2016 cm" band (U = 0-66-0-72). 

SEC-viscometry used with Mark-Houwink coefficients, the errors in the determination of the MWD are less than in conventional SEC. In SEC-viscometry with universal calibration, these errors are greater, as shown in Figure 8. A detailed discussion on the effect of band broadening with viscometers and lightscattering detectors can be found in Reference 39. 

The preliminary estimation of the anisotropic viscosity coefficients Tiii and for solutions of an aromatic polyamide was performed in [57, 58]. Flow cells combined with an IR spectrophotometer were used in these studies to determine the values of angles 0 and (p. Angle (p was small (2-3°), and it was thus assumed that the molecules lie in the shear plane, and angle 6 was estimated with the dichroism of one of the n bands of poly-p-benzamide (PBA). Measurements of the torque in the moving cylinder of a rotary viscometer conducted in parallel with measurements of the velocity of fall of a ball along the axis of the cylinders in the space between them demonstrated the differences in the values of the longitudinal and transverse Tij viscosities. 

The character of the evolution of the flow curves when they are successively taken during prolonged holding of a solution in the working unit of a viscometer can serve as indirect confirmation of the correlation of the shape of the flow curve with the textural inhomogeneity of the sample. As an example, data on the dependence of the heat flux on y for solutions of PBA are shown in Fig. 9.14 [79]. The gradual approach of the curves to the Newtonian is evident, which is naturally correlated with an increase in the orientational homogeneity of the solution which takes place in time. A similar conclusion was also drawn in [80] based on a study of the dispersion of the IR dichroism of the S band of PBA over the width of the cuvette in time. 

Viscosity measurements were performed with an automatic (Fica Viscomatic MS) Oswald type capillary viscometer. Fluorescence emission spectra of pyrene were recorded between 355 and 480 nm on a Fica 65 MK II spectrofluorimeter. The excitation wavelength was 334 nm and the band paths were set at 7.5 nm for excitation and at 0.5 nm for emission. The IJI ratio was calculated as the ratio of the intensity at 373 nm to that of 384 nm. All the measurements were conducted at 25.0 + 0.1 °C. 

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