50 JOURNAL OF COSMETIC SCIENCE and consisted of the following: Deionized water 87.0 %, polymer 1.0 %, hydrogen peroxide (50%) 12.0%, ammonium hydroxide (29.9 %) q.s. to desired pH (by weight). Accelerated Aging of Samples: Triplicate samples of the peroxide gels were placed on stability at room temperature and at 45 ø C in opaque polyethylene containers. Samples were tested at intervals of 1, 2, 4, 8, and 12 weeks. Samples were evaluated for the following properties: pH, viscosity (Teflon coated spindles were used), % active peroxide, and appearance. The active peroxide was determined using the USP monograph assay for hydrogen peroxide (potassium permanganate titration). The peroxide gel samples were also tested for peroxide stability using an industry accepted peroxide "boil test". Application Testing of Samples: 1. High pH Viscosity_ Response: To test the high pH thickening efficiency of the peroxide gel samples, 5% •, ammonium hydroxide was added to each sample to achieve a pH of 10.0. The pH, viscosity, and appearance of each sample was recorded after 3 minutes. 2. Two-Part Mock Hair Color Formula: In order to test if the hydrogen peroxide gels would respond appropriately in two-part permanent hair color applications, a "mock" formula test was performed on each sample. The test was as follows: Equal portions of Part B was added to Part A and mixed. The polymer concentration in the final mixture was 0.5% •. The appearance, pH, and viscosity measurements were recorded after mixing at 3 minutes. Formula: Part A: Hydrogen Peroxide (6 % w• ) Gel Phase (1% w• polymer) Part B: High pH phase (8 % w• ammonium hydroxide) 3. Commercial Hair Dye: In order to test if the peroxide gel samples would thicken in an actual two-part hair dye application, five commercial permanent hair dyes were purchased. The "peroxide developer sample" made with Polymer D (pH 2.7) was selected to mix with the color phase of each commercial hair dye sample because of the data obtained from the previous two experiments. Results: Accelerated Stability Testing Results: 1. Study I The hydrogen peroxide stability in the gel samples after 24 weeks of accelerated stability at 45 ø C showed no loss of hydrogen peroxide over time, except when a high level of hydrogen peroxide (12.0 % w• ) and a high pH (4.5) was combined, where only about 4 % loss occurred ( data will be shown in presentation). The viscosity was also very stable in most samples until week 16, when some viscosity loss occurred. This viscosity loss only occurred in samples with a high level of peroxide (12.0 % w• ) and/or a high pH (4.5). 2. Study II: The initial viscosity of the peroxide gels made in this experiment (as seen in fig. 2) is directly related to pH. Gels made with the cross-linked acrylic acid polymers have a low viscosity at a pH of 2.7 and a hazy appearance. Gels made at pHs of 3.6 and 4.0 are a very viscous clear gel while the associative thickener (polymer E) did not thicken at any pH (see fig. 2). At the current writing of this article, we have completed 8 weeks of accelerated stability at 45 ø C of the peroxide gel samples. The accelerated stability of the hydrogen peroxide samples shows no loss of hydrogen peroxide (see fig. 3). The viscosity results of the gel samples made with peroxide "A" shows no loss of viscosity at a pH of 2.7, but do show some viscosity loss at pH values of 3.6 and 4.0 after 8 weeks of accelerated stability (see fig. 4 & 5). Application Testing Results: 1. High pH Viscosity. Response: Appearance, viscosity, and pH values were recorded after the addition of 5 % w• ammonium hydroxide to the peroxide gel samples. The pH for all samples was 10.0 +/- 0.1. The viscosity of the neutralized cross-linked acrylic acid gels ranged from 1,000 - 18,500 cP (measured after 3 minutes), while the gels made with a liquid acrylic associative polymer only attained viscosities of 55 - 1070 cP. Samples made with Polymer D resulted in the highest viscosities (see fig. 6). The neutralized gels appeared hazy except those made with Polymer D, which were very clear. 2. Two-Part Mock Hair Color Formula: Part A and Part B were mixed together as described above. The pH of all samples resulted in 9.9 +/- 0.1. The viscosity of the cross-linked acrylic acid neutralized gels ranged from 85 - 6,200 cP (measured after 3 minutes), while the gels made with a liquid acrylic associative polymer only attained viscosities of 10 - 25 cP. Samples made with Polymer D again resulted in the highest viscosities and best clarity. 3. Commercial Hair Dye: Five dark brown commercial permanent hair dyes were mixed according to their directions. The dye phase from each of these commercial hair dyes was also mixed at a 50/50 ratio with the "peroxide developer sample" made with Polymer D (pH 2.7). Viscosity and pH of the dye mixtures were all measured after 3 minutes. The pH values of the standard and test sample mixtures were very similar. The "Polymer D developer" produced much higher viscosities compared to that of the standard in most hair colors that were tested. For example, the viscosity of the hair dye "A" mixture was 1,230 cP (standard) and 7,470 cP (Polymer D developer). Conclusions: From the results of this study, it has been demonstrated that cross-linked acrylic acid polymers are very stable in peroxide containing systems and are an ideal thickener for two-part permanent hair dye applications. In particular, we

PREPRINTS OF THE 1997 ANNUAL SCIENTIFIC MEETING 51 recommend Polymer D, which is an easy dispersing acrylic acid copolymer, because of its efficient viscosity building characteristics and clarity when exposed to high pH environments. Polymer D has a very low dispersion viscosity at low pH (2.7), which is ideal for a low viscosity peroxide developer phase, but can also make a stable viscous gel at a pH of 3.6, which is ideal for a hair bleach gel application. Polymer D is an excellent choice to thicken peroxide-containing systems with or without surfactants, unlike the associative thickener studied here that may only thicken at a very high polymer concentration or in combination with other surfactants. In addition, cross-linked acrylic acid polymers offer the following advantages: capability to buffer pH, vertical cling (no-drip rheology), shear-thinning properties, and no odor. Polymers Used in Hydrogen Peroxide Thickening Study- 1% Solids POLYMER • INCI NAME DESCRIPTION Pølymlt A C•øme HIghly crOll-IIn kid hem •olym It • ice/Ik .cid. p•ymmt•d • cyclehew. Polymlr C ClrbOm .r Elly dilp•lin•, h•hly CrOll-ilnked hom•pollnnl M ic•11c idd, po•nn ifLTid In • .Cealb, and P•lfO Acryllm/C10-30 AJkyl EII¾ dllp•rllng, emil-linked copo•/mlt M Acfylll• C•o11•o¾11e•: ic lyli½ icld. polyllll• Fig. I Viscosity of Hydrogen Peroxide Gels As a Function of pH 1ooooo 10000 lOOO loo lo 1 Hydroge#Pore•dl'A'Ulld 2.7 3.6 4 pH • Fig. 2 Hydrogen Peroxide Stability of Gels Thickened with Acrylic Acid Polymers pH 4.0, 6% Peroxide Initill 4 Sloblilly W#kl ß 45 * c Peroxid, 'A' ulsd ..• Fig. 3 Viscosity Stability of Hydrogen Peroxide Gels Thickened with Acrylic Acid Polymers Polymer D, 6% Peroxide •oo,ooo lO,OOO • loo Inlbll I 2 4 Hydrogen Peroxide 'A' UlOd S[iblllt¾ Wlekl • 45' C Fig. 4 Viscosity Stability of Hydrogen Peroxide Gels Thickened with Acrylic Acid Polymers pH 4.0, 6% Peroxide 1oo.oo• •• -- _ 3. Polymer A lO,0O0 .,irl -i- i, Polymer B 1 .ooo 15, Polymer c 21, Poty•,r O •1. Poly•or E Hydrogen Pem•M, 'A' ..d High pH Viscosity Response of Peroxide Gels -- pH 10 1% polymer Concontrition Hydrooen Peruride 'A' ultd • Fig. 5 Fig. 6