EFFECTS OF CHLORINE ON HAIR 241 Figure 8a. 10 cycles of chlorination at 50 ppm and pH 2, showing "with" scale rubbing. Figure 8b. 20 cycles of chlorination at 50 ppm and pH 2, showing "against" scale rubbing. surface layers. The depth of deformation is found to increase with the number of cycles, and after 20 cycles at pH 2, the dissolution combined with the frictional deformation was severe enough to reveal the underlying cortex (Figure 8b). SUMMARY The frictional properties of human hair are affected by chlorine concentration, number of cycles of treatment, and the pH of the solution. In general, the effect of treatment variables, namely the concentration of chlorine, acidity of the solution, and the number of cycles of chlorination, was to increase the average value of the coefficient of friction, alter the nature of the stick-slip profile, and decrease the level of DFE. These results can be understood from the changes in surface morphology of the fiber, especially along paths where fibers had rubbed during friction tests. This examination clearly revealed that the general effect of chlorination was to soften the cuticular surface and reduce the scale definition. The effects of various treatment factors were generally cumulative. An important observation of this study was that the effect of a treatment variable was often more evident in a change in the nature of the stick-slip profile than in the average values of the frictional coefficients. Since inter-fiber friction is an important characteristic of human hair, a careful analysis of this complex parameter can yield much useful information about the morphology of the fiber and the state of its surface. REFERENCES (•) F. P. Bowden and D. Tabor, T/•e Frictio• a•d L•rica•/o• of So/ids, (Oxford University Press, London, 1950, revised reprint, •954).

242 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (2) K. W. Wolf, "An Experimental Study of Interfiber Friction in Surgical Sutures by the Twist Method," Master's Thesis, North Carolina State University (1979). (3) D.C. Prevorsek, R. H. Butler, Y. D. Kwon, G. E. R. Lamb, and R. K. Sharma, Influence of fibre properties on wrinkling behavior of fabrics VII. Effects of morphology on fibre properties, Text. Res. J., 47, 107-126 (1977). (4) Handbook of Chemistry and Physics, 55th ed., R. C. Weast, Ed., (CRC Press, Cleveland, 1974), p D120. (5) J. Lindberg and N. Gralen, Measurement of friction between single fibers II. Frictional properties of wool fibers measured by the fiber-twist method, Text. Res. J, 18, 287-301 (1948). (6) B. S. Gupta, Unpublished Research Work. (7) J. H. Bradbury, The theory of shrinkproofing wool part II: Chemical modification of the fiber surface and its effect on felting shrinkage, friction and microscopic appearance, Text. Res. J., 31,735-743 (1961). (8) K. R. Makinson, Some new observations on the effects of mild shrinkproofing treatments on wool fibers, Text. Res. J, 38, 831-841 (1968). (9) K. R. Makinson, Mechanisms involved in shrinkproofing by degradative treatments, AppL Po]ym. Sym., #18, 1083-1096 (1971). (10) K. R. Makinson and I. C. Watt, Some physical effects of acid wet chlorination on wool fibers in relation to its use as a shrinkproofing treatment for wool, Text. Res. J, 42,698-703 (1972). (11) K. R. Makinson, The role of chlorine in oxidative antifelting treatments of wool, Text. Res. J, 44, 856-857 (1974). (12) F. Alexander and D. Gough, The reaction of oxidizing agents with wool 4. The reactivity of tyrosine, Biochem. J., 48, 504-511 (1951). (13) H. Zimmerman, Felt resistant wool by wet chlorination, Am. DyestuffReptr., 36, 473-476 (1947). (14) L. Shapiro, Shrinkage control of wool by wet chlorination, Am. DyestuffRptr., 37, 376-380 (1948). (15) P. Alexander, R. F. Hudson, and M. Fox, The reaction of oxidizing agents with wool I. The division of cystine into two fractions of widely differing reactivities, Biochem. J., 46, 27-32 (1950). (16) P. Alexander, D. Gough, and R. F. Hudson, The reaction of oxidizing agents with wool 3. The influence of the morphology on the rate of reaction, Biochem. J, 48, 20-27 (1951). (17) P. Alexander, M. Fox, and R. F. Hudson, The reaction of oxidizing agents with wool 5. The oxidation products of the disulphide bond and the formation of a sulphonamide in the peptide chain, Blochem. J., 49, 129-138 (1951). (18) M. Harris and D. Frishman, Some aspects of the chlorination of wool to produce shrink resistance, Am. DyestuffReptr., 37, 52-55 (1948). (19) G. Valk, Reaction between chlorine and wool proteins, Proc. 3rd Int. IVool Text. Res. Conf, Paris, 2, 371-381 (1965). (20) A. Kantouch and S. H. A. Fattah, Oxidation of wool with chlorine and some chlorinated compounds, App/. Po/ym. Symp. #18, 317-323 (1971).