58 JOURNAL OF COSMETIC SCIENCE Accumulation of humectant in stratum corneum: After the application twice a day for 10 days by the above m•thod, the concentration profile ofdipmpylene glycol in stratum comeurn and the skin-moisturizing effect had no remarkable change. On the other hand, glyceml was accumulated in stratum comeurn upon the continuation of use for 10 days with showing its skin-moisturizing effect. When 20 mL of I 0 % glyceml aqueous solution was applied twice daily for 10 days to 20 cm 2 forearm skin and then stopped to apply, glyceml concentration profile in stratum comeurn and skin-moisturizing effect were investigated. Maximum concentration of glyceml in stratum comeurn was approximately 20-30% of weight of stratum comeurn, and skin-moisturizing effect corresponded to the amount of absorbed glyceml in stratum comeum. Conclusion These results suggested that (1) the skin-moisturizing effect depends on the amount of absorbed humeclant and their physico-chemical property in stratum corneum and (2) the excellent skin-moisturizing effect of glycerol is due to the high accumulation of glyceroi in stratum comeurn. References Glyceroi I) D. L. Bisse•t et al., J. 250 Soc. Cosmet. Chem., 35, 345 (1984) •. 200 2) M.D. Batt et al., J. Soc. Cosmet. Chem• 39, " • 150 367(1988) 3) A. Rawlings et al., • •o 100 Arch Dermatol Res, 287, 457 (1995) • "• 50 0 Dipropylene glycol 0 3 0 3 I I Stratum comeurn weight (mg)* Stratum comeum weight (mg)* Fig. 2 Concentration profile of polyoI in stratum corncure at 0, I, and 6 h after application The open square (D) represents the amount of polyol in sWatum comenm immediately after application the open circle (O), that after 1 h the closed square (1), that after 6 h. The asterisk (*) indicate the integrated weight of stratum corneum obtained by tape-stripping and correspond to the depth of horny layer. MEASUREMENT TECHNIQUES LEADING TO IMPROVED ON-HAIR PERFORMANCE OF LOW VOC HAIR SPRAYS G.T. Martino, J.L. Gormley, M.J. Vitale, J.G.L. Pluyter National Starch and Chemical Co., 10 Finderne Ave., Bridgewater, New Jersey 08807 INTRODUCTION The California Air Resource Board (CARB) and other State agencies are moving to reduce the volatile organic compound (VOC) emissions generated by cosmetic and household products, in order to improve air quality. As the VOC contern of hairspray formulations in the U.S. are lowered from -95% in the early 1990's to 55% VOC by June I, 1999, a great effort has been undertaken by formulators and raw material suppliers to maimain the proper performance propertiesL The most cost effective low VOC formulations involve the replacement of organic solvents with water. Unfortunately, water has a deleterious effect on just about every property that is critical to hairspray performance TM. Optimization of low VOC formulations requires a detailed knowledge of the correlation between the formulation physical properties and the on-hair performance properties. In this presentation, the relationship between fundamental physical / surface chemistry with hairspray performance will be discussed. Objective testing methods will be used to demonstrate the importance of physical properties such as wetting, viscosity, dynamic surface tension, pH, and polymer composition on performance properties such as spray aesthetics, drying time, hold, stiffness, and corrosion. RESULTS AND DISCUSSION WETTING: For a hairspray to perform optimally the formulation must coat adjacent hairs and create a bond, which results in the properties of hold and stiffness. The length, continuity, adhesion and toughness of this

PREPRINTS OF THE 1997 ANNUAL SCIENTIFIC MEETING 59 bond contributes to the effectiveness of the formulation. Anhydrous hairsprays of the past had excellent wetting, with a contact angle between the formulation and hair that approached 0 ø. As the water content is increased, to attain low VOC formulations, the contact angle increases and wetting along the hair is hindered. In order to maximize performance, contact angle must be minimized. Capillary wicking is another wetting mechanism ')r the formation of hair/polymer bonds. This phenomenon is also maximized by low viscosity and contact angle. Wicking was measured by plotting weight gain of a hair bundle, in contact with a hairspray formulation, over time. In high water, low VOC systems dioctylsulfosuccinate resulted in large increases in wicking rates. VISCOSITY: High viscosity will impede the sprayability, flow out and film formation of a formulation on hair. Unfortunately for the formulatot and ultimately, the consumer, high water 55% VOC systems tend to result in the highest viscosity compared to higher VOC and alcohol-free systems. Lower molecular weight polymers are usually employed to counter this problem. However, these polymers tend to result in more brittle films and less hold compared to their higher molecular weight analogues. The use of additives and well designed blends of polymers have proven to be effective in approaching an optimum system. DYNAMIC SURFACE TENSION: Dynamic surface tension reduction is critical in achieving acceptable spray aesthetics. Although surface tension is mainly influenced by the solvent system (ie: amount of water in the formulation), additives can be employed that minimize the problem. The surface tension reducing agent must be able to migrate extremely quickly to the air / liquid intekface in order to be effective. The Kruss BP2 bubble tensiometer was used to demonstrate that cyclomethicone is a superior additive to address this problem. pH: The formulation pH and ionicity greatly affects the corrosivity of dimethyl ether / water systems toward tin plated steel cans. Polymer systems below a pH of 7.5 are more corrosive than those above that pH. Polymer composition and neutralization were examined relative to corrosion potential. POLYMER COMPOSITION: Polymer composition, molecular weight, neutralization and Tg were examined for their effect on solution surface tension and viscosity, fill toughness, and on-hair stiffness. The use of inorganic neutralization agents and polymer molecular weight had the largest impact on stiffness. Polymer molecular weight and composition had the largest effect on polymer toughness and viscosity. The hair fixative polymer identified by the INCI name of Acrylates Copolymer ( butyl acrylate/methyl methacrylate/methacrylic acid ) was used as the control in these experiments. CONCLUSIONS: For the hair spray formulatots in and the suppliers to the hairspray industry, it is obvious that in order to achieve water-containing hair sprays having performance which approaches that to which the consumer is accustomed, a thorough understanding of the physical and chemical mechanism of hair spray effectiveness is required. These studies have taken into account all aspects {af the hair spray system. This understanding has being obtained through the development of new and applied analytical techniques and fundamental studies. Preliminary results have given indications of how to approach these difficult formulation problems. In order to optimize the performance of water-containing low VOC hair sprays the number, strength and length of the polymer bond between hair fibers must 'be maximized. One method to achieve this was to maximize the flow of the formula once sprayed onto the hair. It has been shown that flow can be increased by reducing the viscosity and contact angle of theformulation liquid on hair. Polymer composition is an extremely important parameter in achieving the optimum system the polymer predominantly controls the spray aesthetics, stiffness, long term holding power, feel characteristics, and corrosivity. Several additives were identified which also aid in optimizing the desired performance. The ideal high water low VOC hairspray systems must be built from the ground up taking advantage of the newest technology in all formulation aspects. Polymer, solvent, propellant, additive, and delivery system must be optimized interdependently to achieve a hairspray which will satisfy a discerning consumer. REFERENCES: 1. California Code of Regulations, Title 17, Subchapter 8.5 2. G.T. Martino, J. V. Russo, N. A. Morawsky and J. J. Guth, Spray Tech. and Marketing, 2, 3, 34 (1992) 3. N. Morawsky, G. Martino and C. Bushy, Spray Tech. and Marketing, 3, 5, 57 (1993) 4. J. Guth G. Martino, and J. Russo, Selfen-Ole-Fette-Wachse, 117, 13, 464 (1991)