Table 1.
Characteristic relaxation times of PSF and t-PSF samples at various dilution factors, determined from stagnation point birefringence measurements in a cross-slot device.
Figure 1.
Birefringence in the cross-slots for a porcine synovial fluid (PSF) sample diluted by a factor of 20× with phosphate-buffered saline (PBS).
(a) An image of a birefringent strand at a nominal strain rate of = 1346 s−1. Flow enters through the vertical channels and exits through the horizontal channels. The image also indicates the coordinate system, with origin at the stagnation point. (b) A line profile across the birefringent strand where pixel values have been averaged between the dashed lines centred on x = 0 as shown in (a). The peak intensity at y = 0 can be taken as the measurement value of Δn for this test case.
Figure 2.
Flow curves of viscosity as a function of shear rate for the various test fluids composed of diluted porcine synovial fluid.
Solid symbols: PSF, hollow symbols t-PSF. The dotted line represents the approximate sensitivity limit of the rheometer.
Figure 3.
Images depicting the evolution of the flow-induced birefringent strand observed along the outflowing axis of the cross-slot device as the strain rate is increased for: (a) a PSF sample at 30× dilution, and (b) a t-PSF sample at 10× dilution.
Figure 4.
Birefringence as a function of the strain rate at the stagnation point of the cross-slots for (a) diluted PSF samples and (b) diluted t-PSF samples.
Figure 5.
Birefringence normalized by the dilution factor for all the test fluids. Solid symbols: PSF, hollow symbols t-PSF.
Figure 6.
Relaxation spectra for (a) diluted PSF samples and (b) diluted t-PSF samples.
The experimental data points (symbols) have been fitted with log-normal distribution functions (solid lines), the peaks of which can be used to obtain characteristic relaxation times for the HA macromolecules.
Figure 7.
Apparent molecular weight distributions for PSF (solid lines) and t-PSF (dashed lines), derived from the log-normal distribution functions fitted to the experimental data shown in Fig. 5.
Table 2.
Weight-average and number-average molecular weights of the PSF and t-PSF samples as determined from analysis of the birefringence versus strain rate plots.