JOURNAL OF COSMETIC SCIENCE 268 solvent affects the fi nal spatial distribution of silicones on the hair sample and does not lead to a totally random distribution. The strength of hair fi ber–fi ber interactions was the lowest for silicone quat (lowest slid- ing angle), and it was the highest for silicone gum (highest angle) (Figure 7). The silicone quat, the amino ABn and the aminosilicone treatment showed a rather low percentage of angles higher than 90° (column 11, Table I). These treatments were characterized by an increased adhesive tangential force from 2.6 μN (untreated) to 3.5–4.2 μN (column 7, Table I). In contrast, the silicone gum treatment wais characterized by a very high per- centage of angles higher than 90° and a strong normal adhesion 1.6 μN (column 9, Table I). Figure 5. Sliding angle histograms of untreated hair and silicone-treated hair (N = 50, X-axis: angle in degrees). Treated hair has 1000 ppm of silicone quat. [Note: Test data. Actual results may vary.] Figure 6. Sliding angle histograms of hair treated with different silicones at constant silicone dose of 3000 ppm (N = 50, X-axis: angle in degrees). Black line is the normal distribution fi t. [Note: Test data. Actual results may vary.]

2008 TRI/PRINCETON CONFERENCE 269 The large normal adhesion displayed by silicone gum may be attributed to the very large molecular weight of this linear fl exible polymer, which may lead to the diffusive inter- penetration of chain segments and entanglement across the fi ber/fi ber interface, provid- ing bond strength (6). In contrast, the much shorter silicone chains of the silicone quat typically do not form entanglement and, therefore, form low-strength contact bonds. Generally, a very signifi cant effect of concentration was observed when concentration was increased from 1000 ppm to 3000 ppm (Table I). The effect of concentration on the aver- age angle was much more pronounced with the amino ABn and aminosilicone than in the case of silicone quat. For the silicone quat, increased concentration primarily infl uenced the percentage of high angle values and the broadness of the distribution. QUALITATIVE RELATIONS TO HAIR VOLUME Based on hair loop experiments, the different treated tresses were separated into 3 groups: Group I: low interaction (silicone quat) Group II: moderate interaction (amino ABn, aminosilicone) Group III: strong interaction (silicone gum) These three groups appeared to correlate qualitatively with three distinct hair assembly behaviors. The untreated curly and relaxed hair in a high humidity environment is shown in Figure 8a. The trees volume of the curly tresses was very high, compared to the relaxed tresses. The turbulence of the chamber air fl ow and the bending forces of the curled fi bers separated the fi bers. The curled fi bers most likely separated due to the weak fi ber–fi ber interactions. The control experiment clearly contrasted with the silicone treated tresses. The tress volume pictures for quat, amino ABn, aminosilicone, and dimethiconol gum are shown in Figure 8b–e. In Group I, at low concentration (1000 ppm), the tress volume was quite similar to the control, whereas the tress volume was reduced at 3000 ppm (Fig- ure 8b). Although the curl shape was maintained, individual fi bers were separated from each other. In contrast, for Group II (aminosilicone, amino ABn), at both 1000 ppm and 3000 ppm concentration levels, the tress volume of the curly hair was reduced compared to the control (Figure 8c–d). At 1000 ppm, the curled fi bers stayed parallel to each other and the wave shape was maintained to a much greater extent than that of the control tress, especially with amino ABn. The collective effects of the moderate fi ber–fi ber inter- Figure 7. Percentage of angle higher than 90° for hair treated with different silicones. [Note: Test data. Actual results may vary.]