2006 TRI/PRINCETON CONFERENCE 317 (4) H. Zahn, F.-J. Wortmann, G. Wortmann, K. Schaefer, R. Hoffman, and R. Finch, "Wool," in Ull- mann's Encycl. Ind. Chem., 6.Ed. (Wiley-VCH, Weinheim, D, 2003). (5) M. Feughelman, A two-phase structure for keratin fibers, Text. Res.]., 29, 223-228 (1959). (6) D. A. D. Parry and P. Steinert, Intermediate filaments: Molecular architecture, assembly, dynamics and polymorphism, Quarterly Rev. Biophys., 32(2), 99-187 (1999). (7) F.-J. Wortmann and H. Deutz, Characterizing keratins using high-pressure differential scanning calorimetry,]. Appl. Polym. Sci., 48, 137-150 (1993). (8) M. Spei and R. Holzem, Thermoanalytical determination of the relative helix content of keratins, Colloid Polym. Sci., 267, 549-551 (1989). (9) V. F. Monteiro, A. P. Maciel, and E. Longo, Thermal analysis of Caucasian human hair,]. Thermal Anal. Calorim. 79, 289-293 (2005). (10) A. R. Haly and J. W. Snaith, Differential thermal analysis of wool-The phase transition endotherm under various conditions, Text. Res.]., 37, 898-907 (1967). (11) F. -J. Wortmann and H. Deutz, Thermal analysis of ortho- and para-cortical cells isolated from wool fibers,]. Appl. Polym. Sci., 68, 1991-1995 (1998). (12) H. Deutz, Thermische und mikroskopische Charakterisierung von Keratinen, PhD-thesis, DWI at RWTH Aachen University of Technology, Aachen, Germany, 1993. (13) F.-J. Wortmann, C. Springob, and G. Sendelbach, Investigations of cosmetically treated human hair by differential scanning calorimetry in water,]. Cosmet. Sci., 53, 219-228 (2002). (14) M. E. Brown, Introduction to Thermal Analysis (Chapman and Hall, New York, 1988). (15) F.-J. Wortmann, C. Popescu, and G. Sendelbach, Nonisothermal denaturation kinetics of human hair and the effects of oxidation, Biopolymers 83, 630-635 (2006). (16) K. Sharp, Entropy-enthalpy compensation: Fact or artefact?, Prat. Sci., 10, 661-667 (2001).

]. Cosmet. Sci., 58, 319-327 Quly/August 2007) Investigations of cosmetic treatments on high-pressure differential scanning calorimetry J.M. MARSH, C. J. CLARKE, K. MEINERT, and R. M DAHLGREN, Procter & Gamble Technical Centres, Rusham Park, Egham Surrey, TW20 9NW U.M.M., C.j.C., R.M.D), and Wella Service GmbH, Berliner Allee 65, D-64274, Darmstadt, Germany (K.M.). Synopsis High Pressure Differential Scanning Calorimetry (HPDSC) can be used to gain information on both the degree of crystallinity in the intermediate filaments (IFs) and the structural rigidity of the surrounding matrix or intermediate filament associated proteins (IF AP) of the hair cortex. We have used HPDSC to measure changes in denaturation temperature (T 0) and enthalpy (OH0) of the crystalline components after treatment with bleach products. Literature reports suggest that a decrease in peak denaturation temperature is indicative of permanent damage to the hair. However, changing the rigidity of the matrix surrounding the IFs, by temporarily changing electrostatic interactions, should also result in a similar decrease in peak tern perature. The complex nature of bleach formulations including oxidants, alkalizers and salts suggests that several of the components could have a non-permanent affect on salt bridges and hydrogen bonds and hence rigidity or viscosity of the matrix. We have compared the denaturation temperature with levels of lightening (dL) and tensile properties of the fiber after treatment both before and after removal of actives from the fiber. It is evident that the HPDSC results are strongly influenced by formulation components and that these changes are reversible with extensive washing or dialysis. Combined with tensile data, it is proposed that a decrease in T0 and OHn following treatment with bleach products can be due to both permanent and reversible changes to either the intermediate filaments or intermediate filament associated proteins of the hair fiber. INTRODUCTION Cosmetic treatments such as bleaching, perming and the use of permanent colorants have been shown to cause changes to the fibre structure of the hair (1-4). These changes are often seen by the consumer as damage such as increased hair breakage, reduced shine and a poor hair feel in both the wet and dry state. It is important to relate these consumer noticeable effects to measurable changes in the fibre structure. One technique that has been used to measure structural changes to hair is High Pressure Differential Scanning Calorimetry (HPDSC) (5-7). The technique records the thermal behaviour of a sample, such as hair, under controlled heating and in a sealed vessel with a known amount of water. The thermal transition observed is in the range 130-180°C and has been related to the denaturation of the hair's keratin structure. The hair 1s a 319