MECHANICAL PROPERTIES OF HAIR 75 ]IFFEBENCE IN RELAXATION INDICES (IRt-IRu] t0 © 5 © , I I I I o q5 0 , , , , , , , i , 2 4 6 8 tO •. t4 t6 19 20 TIME (HURS) Figure 4. Difference in relaxation indices (IRt-IRu) as a function of time after de-immersion as follows: from de-ionized water at 40% RH, (1) from solutions of 5% hydrolyzed wheat proteins and wheat oligosaccharides, (2) from 5% lysine, (3) and 5% silk amino acids, (4) at 40% RH. IRt and IRu are the relaxation indices of treated and untreated fibers, respectively. 9, where it can be seen that for fibers conditioned at 87% RH, the F(1) increments were positive for LiCI and CaCI 2 and negative for NaCI and MgCI2 at saturation levels. A time recovery pattern similar to that presented by fibers de-immersed from de-ionized water was seen to characterize the withdrawal of hair from the salt solutions. The more striking effects of these ionic solutions were, however, those displayed by the fiber at equilibrium after de-immersion without rinsing the fibers. Figures 5, 6, and 7 depict the hysteresis cycles of F(1)s, IRs, and lengths, respectively, for the untreated and treated fibers. It can be noted that while there are no significant differences on the hysteresis characteristics of F(1)s before and after treatment, the hysteresis values of the IRs and length increments have been shifted to higher levels. The magnitude of these shifts seemed to decrease with this type of salts in the same order as described earlier (see Figure 6). These results can be interpreted in the following way: the presence of these ions, in particular those of LiCI, on the treated hair leaves intact its F(1), or capacity to respond to very rapid deformations. However, because of the large increments in short- term relaxation and fiber dimensions induced by these ions, the hair is more plastic and softer to permanent strains than the untreated hair. It is noteworthy to mention here that the effects mentioned above partially faded when the fiber was thoroughly rinsed. Upon immersion in citric acid solutions, hair acted very much in the same manner as that described for the above-mentioned salts. The main difference was that citric acid did not seem to cause any aftereffect on the hair's F(1), IR, and length hysteresis values.

76 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Fill [g•fl B -- 1 -•-2 .-F-3 •- 4 0-6 D I I I I I I I I I I I•TIVE HUMIDIll Figure 5. Hysteresis curves of F(1) after 10 minutes of fiber treatment in de-ionized water, (1) 5% LiCI, (2) 5% CaC12, (3) 5% MgC12, (4) 5% NaCI, (5) and 5% urea, (6). INDEX OF RELAXATION © 0 I I I I I I I I I O tO 20 30 • 50 • 70 II 90 t• % OF RELATIVE •IOIll Figure 6. Hysteresis curves of relaxation indices after 10 minutes of fiber treatment in de-ionized water, (5) 5% MgCI2, (4 O) 5% NaC1, (4 •*) 5% CaCI2, (3) 5% urea, (2) and 5% LiC1, (1).