EFFECT OF POLYMERS AND SURFACTANTS 251 120 lOO 80 e 60 -• 40 fl. 20 -20 UntreatedProtWhea•/Hydroly .... - .... '" PVP/DMAPA Acrylates Copolymer Quatemium 70 0 20 40 60 80 100 120 140 160 Distance (mm) Figure 4. Combing curve differences for light-brown fibers treated with the indicated compounds and subjected to 12 min of thermal treatment at 152øC. It should also be mentioned that the thermal treatment of Piedmont hair, pretreated with sodium bisulfite, yielded very high increases in combing forces and combing work values. After 10 min of thermal exposure at 152øC, the combing work values for sodium bisulfite-treated hair were in the range of 900-1100 G'cm as compared to 180-200 G ß cm for untreated samples of Piedmont hair. The damaging effect of sodium bisulfite may be attributed to the ability of this compound to break disulfide linkages with the formation of thiol and Bunte salt groups (18), reactions that could also affect the structural elements of the hair surface. In order to provide further evidence for the surface effects illustrated by the data presented in Figure 4, we have carried out the kinetic studies of combing analysis for curling iron application at two temperatures. Figures 5 and 6 display combing work difference (calculated by integrating combing force curves in the thermally affected section of a tress) as a function of thermal treatment time for curling iron temperatures of 132øC and 152øC. It should be stressed that, as in Figures 2 and 3, the combing data were obtained after each 4-min period of thermal exposure, consisting of 1-min heating cycles, in which the tresses were shampooed after each 2-min cycle. The data illustrate a gradual increase in combing work for the untreated control, and an even more pro- nounced increase for protein-treated hair at both temperatures. The use of both cationic polymer and cationic surfactant resulted in low combing work values and no combing force increases as a function of time. TEXTURAL PROPERTIES Throughout the course of our experiments, we have observed changes in the textural

252 JOURNAL OF COSMETIC SCIENCE 400 350 250 200 100 50 1 ::il.i -::::::•: •- .::•.:4 :• '•::::'"•: ' :.:::'i? • 4 minutes [] PVP/DMAPA Acrylates Copolymer [] Quaternium 70 [] Hydrolyzed Wheat Protein [] untreated T • ,• ..•.:: ......... --.:. ½•. :•: '[•j• :.• • . ' .... 8 minutes ?. . . .. 12 minutes Figure 5. Combing work difference as a function of thermal treatment time for light-brown fibers treated with the indicated compounds and subjected to a curling iron temperature of 132øC. 450 400 3,5O m 250 •_. 200 E o 50 -lOO [] PVP/DMAPA Acrylates Copolymer [] Quaternium 70 [] Hydrolyzed Wheat Protein [] untreated 4 minutes 8 minutes 12 minutes Figure 6. Combing work difference as a function of thermal treatment time for light-brown fibers treated with the indicated compounds and subjected to a curling iron temperature of 152øC.