CLEANING HAIR 317 TEN-CYCLE DATA AND BUILD-UP OF SOIL The ten-cycle data (0.01% surfactant) indicate differences relative to the one-cycle data. For the superior lipid soil surfactant SLES-2, there is no change in removal order of the components or in total percent sebum removed (Figure 3). However, there are differ- ences in the ability of SLES-2 to remove different sebum components (p = 0.001). Two distinct groupings of components emerge: the esters and waxes are more difficult to remove than the rest (95% confidence level). These data show some selectivity for SLES-2, but it should be noted that removal of all components is high, i.e., )90% There are, however, changes in the removal order for both ALS and SODS-1 compared to their one-cycle behaviors (Figures 4 and 5), and the difference between ALS and the latter surfactant has narrowed. For one-cycle the total sebum removal figures are 72.4% and 40.7%, respectively (significantly different at 95% confidence level) for ten cycles they are 65.2% and 59.2% (not significantly different). The detergency behavior exhibited by the SODS-1 surfactant is as follows (Figure 4 portrays the one- and ten-cycle data for this material). The dominant feature is the large increase in percent removal of the ester and paraffin wax fractions after ten cycles. In fact, all sebum components show increased removal to some extent for the aforemen- tioned components this increase is substantial. These results may indicate a soil release mechanism is occurring: SODS-1 may be adsorbing onto the hair during subsequent washes, thus preventing further adsorption of certain sebum components. Regardless, the data show that extended use of this surfactant does not induce build-up, but rather enhances removal. 1 Cycle 10 Cycles lOO 8o ß 60 o e &o 2o o c 14 c 16 c 18:21 c 18 P.W. CHOL. EST. 8ebum Component Figure 3. Removal of sebum components by SLES-2 for one and ten soil/wash cycles.
318 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS lOO I Cycle 10 Cycles 8O ß 60 o (o 2o o c14 c16 c18:21 c18 P.W. CHOL. EST. 8ebum Component Figure 4. Removal of sebum components by C8,• o- lEO for one and ten soil/wash cycles. When data are analyzed (Figure 5) for component residues after ten soil/wash cycles with ALS detergent, there is a decrease in removal for the saturated fatty acid fractions (compared to one-cycle behavior), perhaps indicative of build-up or selective cleaning. The removal of cholesterol, unsaturated acid, ester, and paraffin wax fractions is similar to the one-cycle level. At the 95% confidence level cholesterol removal is different from the rest (except unsat- urated acids) saturated acid fractions remain more readily on the hair. There is distinct evidence of build-up of the saturated fatty acid materials (Ct4, Ct6, and C•8) on the hair. This build-up is probably due to the interaction between water hardness (Ca 2 +, Mg 2+ ions), the fatty acids, and ALS. The tap water used in our experiments is 75-80 ppm (as CaCO3) , higher than the 60 ppm reported in reference 7. SLES-2 and SODS-1 do not show this behavior the ethoxy units apparently aid in preventing this hard water reaction. In a separate experiment in which 3.5-g hair tresses were successively soiled and hand- washed (ten soil/wash cycles soil aged overnight between washings), the detergency of 10% ALS and SLES-2 to clean sebum from hair was compared. ESCA data confirmed an increase of calcium ion on the ALS-washed hair as compared to SLES-2 washed tresses. Also, panelists evaluated the ALS-washed tresses to be significantly duller (95% confi- dence level) than the SLES-2 treated hair. The dulling is presumably a manifestation of the fatty acid residue build-up. These ALS data affirm that ALS is a good surfactant, although its sebum removal efficacy is less than that for SLES-2. The results are again in accord with surfactant
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