8 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS where L o is the length of the tress at time 0, L• is the initial length of the tress, and L t is the length of the tress at time t. SUBSTANTIVITY EVALUATIONS Substantivity of three ester-modified MQ resins was evaluated by a modified spray method (ASTM•D 1913). This test method describes a procedure used to measure water resistance of hydrophobically modified cloth (see apparatus detail in Figure 3). In the tests performed with the silicone resins, the cloth sample was replaced with poly- carbonate slides on which three drops of test material were applied and evenly spread over the slide with a finger cot. The substances evaluated in this study included silicone resins modified with C•2, C•6, and C•8 (isostearyl) ester groups. Also included in this study, for comparison purposes, were a dimethicone fluid of 350 cst viscosity, an unmodified MQ resin, and an organic ester, isopropyl myristate. Substantivity tests were performed using neat fluids. Rinse cycles consisted of 250-cc aliquots of water, each equilibrated to ambient temperature. Slides were air dried and evaluated visually be- tween each rinse cycle. Two of the ester-modified resins (C•2 and C•8 isostearyl) were then formulated into a prototype sunscreen composition given in Appendix A, Formulation 3, and sent to an independent testing facility for evaluation of SPF values and water resistance properties. A control formulation in which the silicone ester had been replaced with an organic ester, octyl palmirate, was also provided. These evaluations were performed on three panelists characterized as having skin type II or III (see Table IV for skin type classi- fications), using a Xenon arc solar simulator as the ultraviolet light source. Procedures were carried out according to the methods described in the FDA monograph for SPF determinations and water-resistance evaluations. On the first day of the test, fresh product was applied to the panelists' backs and allowed to air dry. The panelists were then irradiated and sent home. Initial SPF values were measured the next day. The sunscreens were then freshly applied to the panelists, who were submerged, after the product had air dried, for 40 rain in warm turbid water, removed for 20 min, allowed to air dry, and then irradiated this process was repeated once more for the 80-min evaluation. The panelists returned the next day and SPF values were measured again. The same two ester-modified siloxysilicate resins were formulated into lipsticks, as shown in Formulation 4 listed in Appendix A, in order to evaluate substantivity prop- erties and reduction of pigment transfer from color cosmetics. A panel of in-house participants was asked to apply each product to half of their lips, both top and bottom. After a 60-sec set time, the panelists blotted their lips on tissue and the amount of pigment transfer was evaluated visually. They were then instructed to reapply the two products and wear them for the rest of the day, making observations on wear charac- teristics and feathering or skin-bleeding properties. RESULTS AND DISCUSSION COMBING ANt) VOLUM• It is known in the art that increasing the organoalkyl content of quaternary ammonium

ORGANOFUNCTIONALIZED SILICONE RESINS 9 Spray Test Apparatus 1913 6" Glass laboratory funnel Rubber covering for ring support Laboratory ring support ( 3 3/4" Inside diameter) ) •, • rubber tubing Spray nozzle ( 19 holes ! ,, • #65 lycarbonsamp0.35")-drill Wood support and stand .. ß 3/8 314 2 3 3 314 6 7 7112 9 314 9.5 19 51 76 •.:5 152 178 190 248 Figure 3. Spray test apparatus utilized in substantivity evaluations, as described in ASTM method D1913. Table IV Classification of Various Skin Types Skin Type Description Classification Type I Always burns easily never tans Sensitive Type II Always burns easily tans minimally Sensitive Type III Burns moderately tans gradually Normal Type IV Burns minimally always tans well Normal Type V Rarely burns tans profusely Insensitive Type VI Never burns deeply pigmented Insensitive