JOURNAL OF COSMETIC SCIENCE 270 actions helped keep the fi bers together and counteracted the forces that separate fi bers. However, the fi bers did not stick to each other. In Group III, tress volume reduction was observed at both 1000 ppm and 3000 ppm. However, at 3000 ppm, fi ber grouping was observed, due to the strong adhesion interactions. When fi ber–fi ber normal adhesion is strong, groups of fi ber stick to each other (Figure 8e). Figure 8. Hair tress pictures after 1 hour at 75% RH and 25°C. In each picture, two tresses on the left are relaxed, two tresses on the right are curly tresses. Silicone dose indicated in ppm: (a) untreated. (b) treated with silicone quat. (c) treated with amino Abn. (d) treated with aminosilicone. (e) treated with silicone gum. [Note: Test results. Actual results may vary.]

2008 TRI/PRINCETON CONFERENCE 271 CONCLUDING REMARKS This study shows that the incline plane fi ber loop method may detect adhesion forces in the range of 1 μN and elegantly separate the tangential and normal components of the fi ber–fi ber interactions. By collecting the data from a large number of sliding events and by controlling fi ber tension, we were able to detect hair surface damage and differentiate silicone treatments. At concentrations of 1000 ppm and above, silicone treatments in- creased the fi ber–fi ber adhesive forces signifi cantly. In addition, we demonstrated that the collective effect of these interactions infl uenced the behavior of curly hair assembly at high humidity. In particular, the study suggests that block copolymer silicone chemistry allows tuning the level of attractive fi ber–fi ber interactions and controlling the quality of the curly hair assembly appearance. Further measurements of the fi ber–fi ber interactions at lower silicone concentrations and different delivery vehicles will be evaluated in the future. REFERENCES (1) B. Bhushan, Nanoscale chacterization of human hair and hair conditioners, Prog. Mater. Sci., 53, 585– 710 (2008). (2) C. R. Robbins, in Chemical and Physical Behavior of Human Hair, 4th ed. (Springer-Verlag, New York, 2002). (3) H. G. Howell and J. Mazur, Amontons’ law and fi bre friction, J. Textile Inst., 44, T59–T69 (1953). (4) M. Kropfgans, S. Musiol, and S. Nienstedt, Silicone quats—Color retention benefi ts and infl uence of structure modifi cations and blending on conditioning, J. Cosmet. Sci., 55, S133–S141 (2004). (5) D. Dowson, History of Tribology (Longman, London and New York, 1979). (6) H. Yoshizawa, Y.-L. Cheng, and J. Israelachvili, Fundamental mechanism of interfacial friction. 1. Rela- tion between adhesion and friction, J. Phys. Chem., 97, 4128–4140 (1993).