148 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS YIGLL• V•L UG Figure 4.--Flow diagrams--synthetic polymer "solutions." $ #EA/?IN&, $/'/•'• $S Figure 5.--Flow diagrams--natural polymer "solutions." •guspension Evaluation Using this pictorial means of classifying the flow properties of a polymer "solution," an insight into the suspending ability of the "solutions"

RHEOLOGY OF HYDROPHILIC POLYMER SOLUTIONS TABLE 1--APPARENT 20 R.P.M. VISCOSITY VS. SAND SUSPENSION 149 Brookfield V20, Sand cps. Material Suspension 22,800 2.5 % Locust bean gum 8 Hr. 9,740 3.0 % Gum tragacanth (homogenized) Permanent 8,360 2.5 % Sodium alginate 2 Hr. 8,040 1.5 % Guar gum 4 Hr. 6,350 0.25% Carboxy vinyl polymer Permanent 5,900 1.5 % Sodium carboxymethylcellulose 3 Hr. 3,200 2.0 % Methyl cellulose 1.5 Hr. 2,560 2.0 % Gum tragacanth (homogenized) 8 Hr. 2,420 0.18% Carboxy vinyl polymer Permanent 2,040 1.5 % Polyethylene oxide 3 Hr. 1,650 25.0 % Polyacrylic acid 1 Hr. 1,600 0.15% Carboxy vinyl polymer 48 Hr. 940 3.0 % Gum tragacanth (low shear prep.) 2 Hr. may be derived. This is in contrast to the common usage of a single point viscosity measurement as a relative means of comparison of polymer "solutions." In Table 1 the apparent 20 r.p.m. viscosity of a series of polymer "solutions" with widely varying flow properties are shown to have no correlation with their ability to suspend Ottawa silica sand. Note in particular the contrast between 2.5 per cent locust bean gum with an apparent 20 r.p.m. viscosity of 22,800 cps. showing complete settling in eight hours and 0.18 per cent carboxy vinyl polymer with a 20 r.p.m. viscosity of 2420 cps. which shows permanent suspension. In addition to the insight gained by observation of a complete flow curve, we can by calculation of an approximate yield value introduce a means of ranking by numerical value which correlates with suspending ability. In Table 2 the polymer "solutions" exhibiting pseudoplastic flow properties have been ranked in descending order of Brookfield yield value. TABLE 2--YIELD VALUE VS. SAND SUSPENSIoN--PsEuDOPLASTIC FLOW MATERIALS Brookfield Ratio Yield (Y.V./V•0) Sand Material Value 100 Suspension 2.5% Locust bean gum 80 0.14 8 Hr. 1.5% Polyethylene oxide 40 2.0 3 Hr. 1.5% Sodium carboxymethylcellulose 36 0.6 3 Hr. 1.5% Guar gum 32 0.4 4 Hr. 2.5% Sodium alginate 16 0.2 2 Hr. 3.0% Gum tragacanth (low shear make-up) 5 0.5 2 Hr. 2.0% Methyl cellulose 0 0 1.5 Hr. A direct correlation between Brookfield yield value and suspending ability is noted, however, in no case is permanent suspension obtained. A low ratio of Brookfield yield value to apparent 20 r.p.m. viscosity is characteristic of the pseudoplastic polymer solutions.