178 JOURNAL OF COSMETIC SCIENCE SELECTING THE OPTIMUM SILICONE PARTICLE SIZE/CATIONIC POLYMER STRUCTURE TO MAXIMIZE SHAMPOO CONDITIONING PERFORMANCE Wing Li, Jennifer Amos, Susan Jordan, Alan Theis and Cal Davis Amerchol Corporation, 171 River Road, Piscataway, NJ 08854 A Subsidiary of The Dow Chemical Company Summary: Cationic hydroxyethylcellulose (HEC) is widely used to deposit and improve the conditioning performance of silicone emulsions in shampoos. In this study, two silicone emulsions of similar viscosity but different particle size, 0.5µm and 20µrn, were tested with a variety of cationic HEC polymers. For the silicone with the smaller particle size, the high molecular weight cationic HEC polymer deposited more silicone onto both damaged and undamaged hair than the lower molecular weight pol ym er. For the silicone emulsion with the larger particle size, the cationic HEC with the lower molecular weight deposited more silicone than the cationic HEC with high molecular weight. Although the large silicone droplet can be easily deposited onto undamaged hair and damaged hair without a deposition aid, the deposition is uncontrolled and variable. Cationic HEC helped to control silicone deposition, yielding consistent, predictable deposition and maintaining good overall conditioning performance. Panel studies showed that the amount of silicone deposited correlated well with conditioning performance. Scanning Electronic Microscope (SEM) analysis confirmed the deposition differences on hair surface. Background: Silicone polymers, especially non-ionic silicone polymers have been commonly used in personal care products for over 50 years (1). Their unique, low surface tension allows easy spreading on keratinous surfaces, such as hair and skin, and provides significant beneficial improvements in sensory properties, such as soft feel and shine. Silicone emulsions are predominantly used because they are easier to handle and formulate than silicone oil. Silicone prepared with the proper emulsifier results in a stable emulsion having a defined particle size. The delivery of silicone to substrates directly from emulsions or from surfactant-containing 'rinse off formulations has been studied. The deposition of the silicone onto hair has been reported to depend on the ionic charge, droplet size and viscosity of the silicone oil emulsion (2, 3). Polycations, such as cationic HEC, are widely used either as conditioning polymers by themselves or in conjunction with other oleaginous materials in both hair and skin care products. The deposition of cationic HEC and silicone from shampoo systems onto hair has been reported (4, 5). The cationic HEC forms a coacervate (polymer-surfactant complex) upon dilution during the application and rinsing of the formulation (6). The coacervate phase separates from the bulk formulation and is deposited on the hair or skin. Insolubles, such as silicone, are entrapped in the coacervate phase and become deposited along with the polymer. The properties of the coacervate are dependent on the surfactant system and polymer affecting the combined deposition of insoluble actives and cationic polymers onto keratinous substrates ( 6, 7). There is no detailed study of the effect of the silicone particle size, in conjunction with polymer parameters, surfactant system, and hair type on deposition of silicone onto hair. In this study, two nonionic silicone emulsions of high molecular weight polydimethylsiloxane with different particle sizes, 0.Sµm and 20µrn, were evaluated with a variety of cationic HEC polymers, hair types and two surfactant systems: (A) 15.5% sodium laureth sulfate (ES-2) / 2.6% disodium cocamphodiacetate (DSCADA). and (B) 4% ammonium lauryl sulfate (ALS) / 13.5% ammonium laureth sulfate (ALES)/ 2.6% cocamdiopropylbetaine (CAPB) / l % sodium chloride. The results indicate that choosing appropriate pol ym ers in conjunction with silicone particle size is critical for formulating "2-in- l" conditioning shampoo having optimum conditioning performance. More important, a simple change in polymer or silicone particle size allows formulators the flexibility to "dial in" desired sensory properties. Experimental Results: Table I: Formulations for stud : Suractant B: ALS/EA-3/CAPBINaCf Particle size No HH PQ-67· No LH HL Pol mers ol mer ol mer 0.5u E-1 E-111 E-V E-IX A-/ A-Ill A-V 20u E-11 E-IV E-VI E-X A-II A-IV A-VI (I) For cationic HEC polymers. the first abbreviation indicates molecular weight and the second abbreviation indicates cationic charge. '"H"" means high and '"L ·· means low. (2) PQ-67 is hydrophobica//y modified cationic HEC of high molecular weight with low cationic charge. (3) Al/ formulations contain 0.25% polymer. except control. and 1% silicone emulsion. (4) Sma/J particle size silicone emulsion and largeparticle size silicone emulsion are DOW Corning" 2-I 352 Em11/sion and DOW Corning"l-1491 Emulsion. respectively. PQ-67 A-VII A-VIII

2005 ANNUAL SCIENTIFIC MEETING 179 Silicone deposition on hair - The total amount of silicone deposited on hair was measured on hair that was treated five times with the prototype formulation listed in Table I. The hair was rinsed and dried between each treatment. Two types of undamaged hair, European brown hair and Asian hair, and one type of damaged hair, commercial bleached hair (all from International Hair Importers and Products Inc.), were used for this study. The silicone was extracted from the hair by a 50/50 (v/v) methyl butyl ketone/ toluene solution, and then measured using atomic absorption spectrophotometry. The results using both surfactant "A" and "B" showed that the structure of the cationic HEC - especially the molecular weight - the silicone droplet size and type of hair all had a very strong impact on silicone deposition. In Figure 1, the formulation containing small silicone particle size (0.5µm) without cationic HEC, such as Formula E-1 gave very poor silicone deposition on all types of hair. However, the formulation containing cationic HEC improved the silicone deposition. For example, the cationic HEC with high molecular weight (HL in Formula E-V), delivered more silicone than the low molecular weight polymer (LH in Formula E-III). The hydrophobically modified cationic HEC, PQ-67, deposited even more silicone on the hair, especially damaged, commercial bleached hair. This trend was reversed with the formulations containing large particle size silicone. Figure 1: Deposition of Small Silicone Particle from Surfactant A in Different Types of Hair 300 250 � • % 200 i 150 g100 in 50 E-1 E-111 E-VE-VII E-IX E-1 E-111 E-V E-IX E-1 E-111 E-V E-IX European Brown Hair Commercial Bleached Hair Asian Hair Figure 2: Deposition of Large Silicone Particles from Surfactant A on Different Types of Hair 3500 3000 � 2500 �2000 � 1500 '::° 1000 ci"i 500 - E-11 ' E-IV E-VI E-VIII E-X E-11 E-VI E-VIII E-X E-11 E-VI E-VIII E-X European Bra'Ml Hair Commerc,al Bleached Hall As,an Hair In Figures 2 and 3 the formulations containing large silicone particle size (20µm) without cationic HEC (Formulas E-II and A-II) yield very high silicone deposition on undamaged hair, such as European brown hair and Asian hair. This phenomenon can be explained by the fact that the attractive Van der Waals forces between particles increase with particle size and, eventually, the large particles tend to adhere better when they collide with another surface (6). However, the silicone deposition measurement shows a big variation of silicone deposition on different hair tresses. This indicates the deposition is uncontrollable and could lead to inconsistent conditioning and eventual silicone build-up. Conversely, the formulation containing cationic HEC yields more consistent and controlled deposition. The data also suggests that when large particle size silicone is used, low molecular weight cationic HEC should be used to maximize deposition onto undamaged hair. This difference in deposition profile may be due to high molecular weight polymers stabilizing the large silicone droplets and preventing them from colliding with the hair surface. The large particle size silicone, however, is relatively easier to deposit onto undamaged, European brown, hair than damaged, commercial bleached, hair regardless of which polymer is used. The bleaching process has significantly modified the hair surface of the commercial bleached hair to a highly negatively charged surface which potentially affects the silicone deposition process. The silicone deposition from the formulation of Surfactant B containing large silicone particles shows a similar trend as the formulation from Surfactant "A" (Figure 2 & 3). However, the relative amount of silicone deposited onto European brown hair from surfactant "B" is much lower than surfactant "A". This demonstrates that the surfactant system can significantly change the silicone deposition process.