EFFECT OF CELLULOSE POLYMERS ON DYE UPTAKE 111 15 dye uptake (µmoll g hair) 10 5 Colour PLUS 250 30M SL-60 Fi gu re 1. Total dye uptake after the dyestuff process. (expressed as µmoles versus gram of hair) for the different samples in the outer and inner layers. The presence of the non-ionic PLUS polymer in the dyestuff composition gives an increase in the uptake of all the dyes in the outer layer of the fiber the other polymers show a behavior similar to that of the control sample. This observation can be due to a fast-forming film of PLUS polymer on the hair surface owing to its higher hydropho- bilicity with respect to the other polymer used. In contrast, when ionic polymers (30M and SL-60) were used in the dyestuff, an improvement (ca. 30%) in the dye amounts in the inner layer is observable. This suggests a penetration of these polymers into the hair. The color measurements were carried out using the samples treated with SL-60 and PLUS polymers, chosen as representative of the two different polymeric classes. In Table III are reported the color parameters: L} a} b} obtained after dyeing (control, Plus, SL-60) and without the dyeing procedure (yak), respectively. The dyestuff treatment always produces a decrease in the L parameters of the fiber, as observable in comparing the data reported in the first column of Table III. When the polymers are present in the dyebath, this effect seems to be weakened. With regard to the color brightness effect, of the total color difference (dE), the chromaticity differences (dC), and the lightness differences (dL), only the last one seems to be affected by the presence of polymer (see data reported in Table IV). The color change in the alb plane seems not to be influenced by the kind of polymer used, as shown in the dC data. Therefore, the presence of polymers in the dyebath seems to concern only the lightness parameters and not the color itself, as confirmed by the absence of differences perceptible to the human eye. HAIR DYE WASH-OUT The effect of the dye mixture wash-out was studied by carrying out extraction tests on tresses after different washing cycles (third, sixth, and ninth, respectively). The percent

112 JOURNAL OF COSMETIC SCIENCE outer layer � · 1.4 +--- - --------------- - - =F----- .ea 1.2 +- - - ------------- ---__. 1 1.0 +------ - - ..=. 0.8 -+-- --- ------------ j 0.6 g- 0.4 -+-----"'1""'---- - -------1 !:. 0.2 HC Blue 2 B.Red 51 inner layer HCYellow2 ■ control CJ PLUS ■250 CJ30M ■SL-60 14.0 �---------------------, "i:" ii 12.0 �- - - - ------- - - - - ---- -----------,- ,e» 10.0 +------------------------,�"T- E 8.0 +--- - ---- - - ------ -- ...3: 6.0 --t---- - ---------· 4.0 ,---- ----------. � 2.0 -,---------------- 0.0 HC Blue2 B.Red 51 HCYellow2 ■ control □ PLUS 30M SL-60 Figure 2. Variation of the µmoles uptake of the different dyes in the function of dyestuff composition. The dye uptake is expressed as µmoles/g hair. The outer layer consists of the hair cuticle the inner layer consists of the hair cortex. Control PLUS SL-60 Yak Table III CIELAB, L, a, b Parameters after Dyeing Process L a 45.2 ± 1.1 22.9 ± 1.4 48.5 ± 3.8 21.3 ± 3.1 46.4 ± 2.2 21.4 ± 3.0 69.3 ± 1.3 0.6 ± 0.1 b 12.6 ± 0.3 8.9 ± 2.0 10.3 ± 0.8 8.7 ± 0.9 The data represent the means of three different measurements. The estimated standard deviation (S.D.) is reported. Yak sample represents the value of the yak tress before dyeing. dye uptake on the hair was then calculated, considering 100% the value obtained after the dyestuff process comprising the first washing cycle. In Figure 3 are reported the data obtained with different dyebaths, compared with the control sample: the PLUS and SL-60 polymers can slow down the fading process during the first washing (third cycle) so that the appearance of freshly dyed hair lasts longer. Beyond the sixth or ninth