1 .01 o o 4- 4- .01 .1 1 10 100 oo (Rad/s) Figure 10. Effect of XG concentration on loss tangent of 1% MAS dispersions. Symbols are the same as for Figure 6. .01 ß ß ß ß o o o O o 4- 0 0 0 ß 0 0 4- 4- 4- 4- + + ß ß ..... i ' ...... i ....... i , ...... .1 1 10 100 O0 (Rad/s) Figure 11. Effect of XG concentration on loss tangent of 3% MAS dispersions. Symbols are the same as for Figure 6.
12 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ACKNOWLEDGMENTS The authors thank Bohlin Rheologi and Schering-Plough for the use of rheometers Mr. Steve Colo of Bohlin Rheologi for helpful discussions and Mr. Ross Clark of Kelco, Mr. Peter Ciullo of R. T. Vanderbilt, and Dr. Michael Kopcha of Schering-Plough for reviewing the manuscript. REFERENCES (1) J. L. Zatz and S. Knapp, Viscosity of xanthan gum solutions at low shear rates, J. Pharm. Sci., 73, 468-471 (1984). (2) M. M. Santore and R. K. Prud'homme, Rheology of a xanthan broth at low stresses and strains, Carbohydrate Polym., 12, 329-335 (1990). (3) W. E. Rochefort and S. Middleman, Rheology of xanthan gum: Salt, temperature, and strain effects in oscillatory and steady shear experiments, J. Rheol., 31, 337-369 (1987). (4) J. L. Zatz and G. P. Kushla, "Gels," in Pharmaceutical Dosage Forms.' Disperse Systems, H. A. Lieher- man, M. M. Rieger, and G. S. Banker, Eds. (Marcel Dekker, New York, 1989), Vol. 2, pp. 495- 510. (5) P. A. Ciullo, Rheological properties of magnesium aluminum silicate/xanthan gum dispersions, J. Soc. Cosmet. Chem., 32, 275-285 (1981). (6) H. A. Barnes, J. F. Hutton, and K. Walters, An Introduction to Rheology (Elsevier, New York, 1989). (7) P. J. Whitcomb, B. J. Ek, and C. W. Macosko, Rheology of xanthan gum solutions, in Extracell. Microb. Polysaccharides Syrup., P. A. Sandford and A. Laskin, Eds. (ACS Symposium Series, Wash- ington, DC, 1977), Vol. 45, pp. 160-173. (8) J. L. Zatz and C. Yarus, Stabilization of sulfamerazine suspensions by xanthan gum, Pharm. Res., 3, 118-121 (1986). (9) J. L. Zatz and B. K. Ip, Stabilization of oil-in-water emulsions by gums, J. Soc. Cosmet. Chem., 37, 329-350 (1986).
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