Polyox viscosity

Of the three worldwide manufacturers of poly(ethylene oxide) resins. Union Carbide Corp. offers the broadest range of products. The primary quaUty control measure for these resins is the concentrated aqueous solution viscosity, which is related to molecular weight. Specifications for Polyox are summarized in Table 4. Additional product specifications frequendy include moisture content, particle size distribution, and residual catalyst by-product level. 

Table 4. Aqueous Solution Viscosity Specifications for Polyox Resins ...

Polyox resin-grade Approx, mol Nominal resin Brookfield Speed, Viscosity at 25°C, Pa-s ... 

Shear Degradation. Aqueous solutions of Polyox were agitated vigorously with a 10-blade stirrer turning at 1080 r.p.m. The solution viscosities were measured at various times during the stirring period. 

Typical Experiment. Polyox resin, Grade WSR-5M5, was transferred to a stainless steel hopper positioned over a vibrating feeder. The belt speed was set at 90 inches per minute, and the accelerator was adjusted (with the shutter closed) to deliver a current of 250 /xa. at 2 m.e.v. The shutter was opened, and the feeder was activated. The calculated dose was 0.75 megarad. After irradiation, the viscosity of each sample was measured. The average 5% aqueous solution viscosity for 27 samples of one particular blend was 78 7 cp., and the average for 16 samples of another was 80 =b 5 cp. 

The striking changes in solution viscosity produced by the cobalt-60 y-ray irradiation of dry Polyox are shown in Table I. 

Table I. Effect on Bulk Viscosity Irradiation of Dry Polyox...

The initial molecular weight is an important factor in Polyox irradiations. The viscosities of 5% aqueous solutions are plotted as a function of total dose in Figure 2. The Polyox powder was irradiated in air with 2-m.e.v. electrons at rates of 200 to 4000 megarads per hour. The samples in decreasing molecular weight were as follows WSR-701, WSR-301, WSR-5M5, and WSR-35. The range is from about 107 to 2 X 10. This... 

The effect of irradiation on the shear stability of Polyox solutions is shown in Figure 3. The viscosities before agitation were comparable, and it is apparent that after doses of approximately 0.4 megarad the solutions are much more stable than the unirradiated control. 

Figure 3.8 Shear viscosity of Baysilone M 1000 silicone oil and aqueous PEO solution (c = 1 wt.-%. Polyox WSR 301)...

The intrinsic viscosity of the Polyox as measured with porous filters is shown in figure 3 The intrinsic viscosity [n] is defined as. 

Figure 3 Intrinsic viscosity of Polyox WSR 301 versus Reynolds number measured with two fi1ters.A Upstream fi1 ter O Downstream filter, 35 mn downstream Downstream filter close to upstream filter...

The relaxation time was estimated by plotting the logarithm of the pressure drop (with the pressure drop at infinite passage time subtracted) versus time, see figure 5. The relaxation time was found to be independent of the concentration of Polyox and of Reynolds number but linear in solvent viscosity. 

Measurements with a one layer mesh screen gave results similar to those obtained with porous filters with high intrinsic viscosity of Polyox, severe degradation, linearity in concentration and onset of pressure drop. Also a relaxation time of about 0.1 seconds was obtained when using screens. Any configuration of screens and porous filters in the test section gave the 0.1 seconds relaxation time. The screen was a wire mesh screen with a wire diameter of 0.05 and a separation between wires of 0.125 mm. 

The check of the above formula was done by comparing the drag coefficient data from the measurements [7] in Polyox coagulant solutions with an intrinsic viscosity of 17.8 dl/gr with present measurements of shedding frequency (with a similar type of polymer, possessing a measured intrinsic viscosity 15 dl/gr) and also with the shedding frequency measurements [8] with polyox WSR-301. All these experiments were carried out at a concentration of 100 ppm (Table 1). 

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