EFFECT OF POLYMERS AND SURFACTANTS 247 Tools, curlin 8 iron (Model SOC125S) manufactured by Continental Hair Products, Glendale, AZ. This curling iron model was chosen for the analyses since its temperature profile was the most representative of the commercially available curling irons. As indicated by our previous studies (5), thermal treatment to each hair tress was admin- istered in the same position in order to maintain experimental uniformity. The thermal treatment of hair was administered for a duration of 1 min, at which time the samples were thoroughly rinsed and pretreated with the indicated compound. The sum of all heating cycles constitutes a total treatment time, normally 12 min in duration. After each 2-min cycle, the samples were thoroughly rinsed, followed by shampooing. After each 4-min cycle, all instrumental measurements were performed. These consisted of combing analysis and texture analysis after thoroughly rinsing the samples and, again, after shampooing the samples. Once the mechanical measurements were completed, we obtained fluorescence spectra in order to monitor the Trp degradation. For each fluo- rescence measurement, readings were obtained from the thermally exposed and unex- posed regions of the hair tress. The hair tress treatments were administered with 1% solutions of the indicated active. The fibers were wetted prior to treatment, followed by towel drying. Then the damp hair was saturated with a solution of active (2.5 8), with the excess amount of treatment removed by paper towel blotting, resulting in a 0.55-8 application of the 1% solution (3.46 m 8 of active/1 8 of hair). The treated tress was then air-dried (23øC) with an Elchim Professional hair dryer (model EC 35227), distributed by Elchim-USA, Inc., Union, NJ. After drying, the hair tresses were subjected to thermal treatment as de- scribed above. Experiments were performed on light-brown hair purchased from Inter- national Hair Importers & Products, Inc., Valhalla, NY, and Piedmont hair, purchased from DeMeo Brothers, Inc., New York, NY. POLYMERS AND SURFACTANTS PVP/DMAPA acrylates copolymer, quaternium 70, and hydrolyzed wheat protein are commercial products sold under the trade names of Styleze CC-10 (ISP), Ceraphyl 70 (ISP), and Hydrotriticum 2000 (Croda), respectively. Additionally, we examined sodium bisulfite (Aldrich), which was used for studies on Piedmont hair. The structures of PVP/DMAPA acrylates copolymer and quaternium 70 are presented in Figure 1. RESULTS AND DISCUSSION SPECTROSCOPIC ANALYSIS The effect of polymers and surfactants on the thermal decomposition of Trp in hair was investigated at 132øC and 152øC, with intermittent heating periods of 1 min, for a total treatment time of either 10 min or 12 min. We also explored other temperatures and treatment schedules in which the observed effects were generally similar to those re- ported for the conditions specified above. The data analysis suggests that the thermal decomposition of Trp may be impeded by pretreatin 8 the fibers with a polymer or surfactant. Figures 2 and 3 demonstrate the progression of Trp damage, on light-brown hair at 132øC and 152øC, as a function of thermal treatment time for an untreated control, and for hair modified with PVP/DMAPA acrylates copolymer, quaternium 70,

248 JOURNAL OF COSMETIC SCIENCE --ClinCH Ha CH•--• C--O I NH PVP/DMAPA Acrylates Copolymer O O C HT'-C-- O--( C H 2 ) 1-•--C H 3 II I C 17 H3-•--C-- N H--(C H2)•-- •--C H3 CH 3 c, © Quaternium 70 Figure 1. Chemical structures of PVP/DMAPA acrylates copolymer and quaternium 70. and hydrolyzed wheat protein. At these temperatures, 12 min exposure of intact hair results in a 27.5% (132øC) and 50.0% (152øC) loss of Trp. The data in Figures 2 and 3 indicate that modified hair undergoes a slower Trp decomposition as compared to untreated hair. For example, hair modified with quaternium 70 and subjected to 12 min of curling iron exposure at 132 øC undergoes a Trp loss of approximately 22%, providing (27.5% - 22%/27.5% x 100% = 20%) a 20% thermal protection factor. The effect of all treatments was similar, with the protective effect ranging from 10% to 20% and evident even after the shortest exposure times (4 min). We conducted similar experi-