THE CHLORINE-HAIR INTERACTION 103 Table IV Effect of Cosmetic Treatment/Sequence and Cycles of Chlorination on the Percent Reduction in Force and Work Required for 20% Extension of Blond Hair Cycles Treatment Force s* n** Work s n 0 Bleach control 7.48 1.14 9 13.02 2.93 8 Dye control 6.41 1.5 ! 7 9.89 3. !2 7 Perm control 43.82 3.40 6 51.54 5.79 6 10 Control 4.03 1.34 11 8.00 3.03 8 Prebleach 14.15 3.42 14 17.50 5.43 14 Postbleach 11.91 2.07 8 17.02 4.60 10 Predye 19.79 4.51 10 24.57 6.02 10 Postdye 12.51 1.94 8 11.96 2.87 7 Preperm 50.93 6.77 10 60.12 6.17 12 Postperm 49.58 4.99 10 54.51 4.46 10 20 Control 7.76 1.61 11 13.35 3.78 8 Prebleach 20.77 2.96 14 24.56 3.93 14 Postbleach 20.77 2.96 9 24.55 4.14 10 Predye 25.17 3.5 ! 10 26.93 5.20 10 Postdye 22.96 4.27 9 21.64 5.44 9 Preperm 58.29 5.58 10 64.56 4.60 ! 2 Postperm 59.86 3.47 8 61.62 5.28 9 30 Control 19. !9 1.75 11 21.62 3.58 8 Prebleach 27.67 2.86 14 32.24 4.28 14 Postbleach 30.26 4.34 7 36.05 4.30 7 Predye 33.83 3.07 10 36.89 3.64 !0 Postdye 31.89 3.99 8 35.48 7.27 10 Preperm 62.50 5.15 10 69.26 4.92 !2 Postperm 65.72 4.32 8 68.14 4.20 8 * s = standard deviation. ** n = number of observations. could be due to the incomplete reformation of disulfide crosslinks. The effect of com- bining the cosmetic treatments with chlorination appeared to be additive. The effect of treatment sequence for each cosmetic treatment, however, was not significant, sug- gesting that both treatment sequences affected the cortex of the fiber to a similar ex- tent. Therefore, the cuticle did not contribute significantly to the tensile properties of wet hair fibers at low extensions (20%). Values of the ratio of knot breaking-to-fiber tenacity are given in Table V. Only perming caused a significant increase in K/T in the control samples. Analysis of vari- ance indicated no significant effect of treatment sequence on the values of this param- eter. All treatments produced a similar significant increase in K/T when cycles of chlo- rination increased from 0 to 15, with no further significant change occurring beyond 15 cycles. These results are similar to those seen in the study of the effect of pH (1). Once again, the results indicated that the treated fibers were more flexible. CONCLUSIONS Two distinct trends were seen when chlorination was combined with cosmetic treat- ments, depending upon whether the treatment was applied to the hair before or after

104 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table V Effect of Cosmetic Treatment/Sequence and Cycles of Chlorination on the Ratio of Knot Breaking-to-Fiber Tenacity (K/T) of Blond Hair Cycles Treatment K/T s* 0 Control 0.600 0.134 Bleach control 0.661 0.055 Dye control 0.630 0.071 Perm control 0. 774 0.077 15 Control 0.924 0.077 Prebleach 0.920 0.118 Post bleach 0.886 0.095 Predye 0.933 0.095 Postdye 0.816 0.045 Preperm 0. 829 0.114 Postperm 0.901 0.089 30 Control 0.955 0.148 Prebleach 0.915 0.096 Postbleach 0.808 0.063 Predye 0.881 0.145 Postdye 0.871 0.055 Preperm 0.955 0.07 ! Postperm 0.844 0.118 * s = standard deviation for eight observations. chlorination. The chlorination procedure was carried out in solutions with 10 ppm chlorine concentration, which is somewhat stronger than typically found in swimming pools. Consequently, the effect of cycles of chlorination seen on the properties examined may be accelerated. The main effect of applying the cosmetic treatment to hair before chlorination was on the wet tensile properties of the fibers. There was a significant decrease in the force required to extend fibers 20% over the decrease given by chlorination alone. The pre- chlorination treatments showed limited effects on interfiber friction, surface mor- phology, weight loss, and knot strength. Postchlorination treatments more greatly affected interfiber friction, cuticular mor- phology, and the weight of the fibers. Both blond and brown hair were affected in a similar manner. The bleaching, dyeing, and perming treatments were strong enough to degrade and remove cuticular material that had been weakened by prior chlorination. This accounted for the smooth appearance of the surfaces, significant weight loss, and, also, the observed decrease in the coefficient of friction of samples chlorinated between 15 and 30 hours. The changes in tensile properties and knot strength were similar to those found with the pretreatments, in spite of greater cuticular damage by posttreat- ment with cosmetic chemicals. REFERENCES (1) N. B. Fair and B. S. Gupta, The chlorine-hair interaction. II. Effect of chlorination at varied pH levels on hair properties,J. Soc. Cosmet. Chem., 38, 371-384 (1987).