MECHANICAL PROPERTIES OF HAIR 79 t00 1 OF Fill VARIATION -tOO ' ' o t 2 I I I I I I I 3 4 5 6 7 8 9 tO TIME (MINUTES) Figure 9. Percentages of F(1) variation as a function of time of fibers immersed in saturated solutions of the following salts: LiCI, (1) CaCI2, (2) MgCI2, (3) NaCl, (4) and de-ionized water, (5). t001[ OF F[t) VARIATIO .,. tOO I I I I , I , I I I , , I I I I , I , I , I I , I , , : - I I I I I I I : ' ][ : [ ' ' :[ ' t ' : [ [ : : 0 5 tO 15 20 25 30 35 40 45 50 T])!E (HZNmES) Figure lO. Percentages of F(1) variation as a function of time of fibers immersed in urea solutions as follows: 35%, (1) 15%, (2) and 5%, (3).

80 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 25 F[1] [gmf] INDEX OF RELAXATIO to -5 0 I I I I I I I I I I ?d % OF RELATIVE HUNIUITY Figure 11. Hysteresis curves of different fibers as follows: F(1) - (1), and IR - (2), of an untreated fiber F(1) - (3), and IR - (4), of a 10-minute-treated fiber in 5% lysine and F(1) - (5), and IR - (6), of a 10-minute-treated fiber in 5% silk amino acids. IMMERSION OF HAIR IN DIFFERENT SOLVENTS AND IN W/O AND O/W EMULSIONS Hair products are often presented in emulsion form and sometimes contain solvents such as glycerine or propylene glycol. It was, therefore, considered appropriate to study the separate effects of glycerine, propylene glycol, propanol, ethanol, and methanol, and also of some w/o and o/w emulsions, on the F(1)s and IRs of hair. Immersion of hair fibers in these liquids resulted again in F(1) and length variations that were strongly dependent on the moisture content of both the fibers and liquids (see Figure 13). The solvents produced increments or decrements in F(1), depending on whether they were conditioned at lower or higher humidities than the hair fibers. In Figure 13 are shown F(1) variations in time of hairs conditioned at 87% RH and immersed in solvents conditioned at 10% RH. It should be pointed out that this type of solvent conditioning effect was only characteristic of glycerine and propylene glycol. The addition of small amounts of water to the solvents eliminated the need for their conditioning, as would be expected. The immersion in w/o and o/w emulsions was found, on the other hand, to induce length extensions and F(1) decrements for all fibers conditioned at relative humidities lower than 87% RH. In Figure 13 it can be appreciated, for instance, that the emulsions decrease the values of F(1) of fibers conditioned at 87% RH, although not as low as in the case of pure de-ionized water. No aftereffect could be detected in the hysteresis cycles of F(1)s, IRs, and length dimensions of fibers de-immersed from all these solvents and