2010 TRI/PRINCETON CONFERENCE 135 CORRELATION BETWEEN REDUCTION IN SURFACE ENERGY AND DECREASE IN COMBING FORCE Surface energy can be used as an indicator of surface reactivity. Higher the surface energy, more hydrophilic the hair surface, and stronger interactions between hair and water and between hair fi bers each other will be. These will generate larger combing forcers during combing processes. Therefore, it is of our interest to establish correlations between reduc- tion in surface energy and decrease in dry/wet combing forces of conditioner-treated hair samples. In this study, bleached and virgin hair were used and treated with conditioners A and B separately. Percentage changes in surface energy, dry combing forces, and wet combing forces on both bleached and virgin hair are plotted together in Figures 9 and 10, correspondingly, for conditioners A and B. It can be seen from Figure 9 that the average surface energy of conditioner-A treated vir- gin and bleached hair reduced about 30%, and corresponding dry and wet combing forces of treated hair tresses decreased about 70% and 90%, respectively. In Figure 10, the reduction in surface energy of conditioner-B treated bleached hair is 33.72%, which is more than the 27.64% for virgin hair. The decrease in dry combing forces for the bleached hair is 71.34%, which is much higher than the 34.96% for the virgin hair. The same trend is observed on reductions in wet combing forces between bleached and virgin hair. Figure 8. Reductions in wet combing forces of conditioner-B treated hair. Figure 9. Reduction of surface energy vs combing force for conditioner-A treated hair.

JOURNAL OF COSMETIC SCIENCE 136 CONCLUSIONS Based on these experimental results, we may conclude: Hair surface energy can be determined by using the Fowkes theory in a two-component 1. liquid system. After conditioner treatment, the combing forces of hair tresses reduced with a decrease 2. in average hair surface energy. The percentage reduction in average surface energy of treated hair fi bers depends on 3. the applied conditioner formulation and the type of hair. The percentage decrease in dry/wet combing forces of cosmetically treated hair tresses 4. also depends on the applied conditioner and the type of hair. Determination of change in average surface energy of cosmetically treated hair samples 5. can be used to evaluate/screen the conditioning performance of applied formulations (ingredients). ACKNOWLEDGMENTS The authors thank Mr. Abhijit Bidaye and Mr. Scott Cardinali of Croda Application Group for providing conditioner formulations. They thank the Research Director, Mr. Abel Pereira, and the Vice President of R&D, Dr. Rob Comber, for their support of the project. REFERENCES (1) Y. I. Tarasevich, Theoretical and Experimental Chemistry, Vol. 42, No. 2 (2006). (2) C. Rulison, Application Note 401 (Augustien Scientifi c). (3) Y. K. Kamath and H-D Weigmann, Modifi cation of human hair through fi ber surface treatments: Char- acterization by wettability, C&T Magazine, 101, 37–49 (1986) (4) Y. K. Kamath, C. J. Dansizer, S. Hornby, and H. D. Weigmann, Surface wettability scanning of long fi laments by a liquid membrane method, Textile Res. J., 57, 205–213 (1987) (5) H. D. Weigmann, Y. K. Kamath, S. B. Ruetsch, P. Busch, and H. Tesmann, Characterization of surface deposits on human hair fi bers, JSCS, 41, 379–390 (1990) (6) F. K. Hansen, “The Measurement of Surface Energy of Polymer by Means of Contact Angles of Liquids on Solid Surfaces”, short overview (University of Oslo). (7) M. Zenkiewick, Methods for the calculation of surface free energy of solids, J. Achiev. Mater. Manuf. Eng. 24(1), 137–145 (2007). Figure 10. Reduction of surface energy vs combing force for conditioner-B treated hair.