AQUEOUS TOPICAL ADHESIVES 117 plied directly on either the back of the hand or on Petri dishes. Despite the subjective nature of the tests, sufficient differences were noted to allow for differentiation of the preparations. In the following discussion of the preparations, the procedure and results are considered in reference to individual resins. Polyvinyl Alcohols The film-forming properties and preparation of aqueous solutions of po!yvinyl alcohols are discussed in detail in technical bulletins and in Part I (4). From the experimental data obtained from the prepara- tion of thirty polyvinyl alcohol concentrates the following was observed: 1. Polyvinyl alcohol rapidly combines with polyethylene glycol to form a gel. 2. Glycerin and sorbitol delay the drying time. 3. Propylene glycol increases the film strength. 4. Triethanolamine markedly increases the viscosity of the con- centrate. 5. Formaldehyde solution USP was the best piasticizer. It has no effect on viscosity, shortens the drying time of the film, improves film strength, and prolongs adhering time. Optimum concen- tration of formaldehyde as a plasticizer for polyvinyl alcohol was 1.6-3.2% (v/v) of the resin concentration. As no free formaldehyde could be detected in the formulations, it was considered to be bound with the polyvinyl alcohol. However, despite the low concentration used and the absence of free formaldehyde, it is realized that the material has potential sensitizing properties and should be carefully tested. Polyvinyl Acetate Unlike polyvinyl alcohol, polyvinyl acetate is not water soluble. Commercial products, such as Gelva ©* aqueous emulsions, are available which form clear continuous films at room temperature. Gelva emul- sions containing 54.5•o of solids were readily diluted with water but were not stable for extended periods of time. * Gelva, a product of Shawinigan Resins Corporation, Springfield, Mass.

118 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Polyvinylpyrrolidone and Copolymers Polyvinylpyrrolidone (PVP) was too soluble in water to prepare films with water resistance. The PVP/vinyl acetate copolymers had less water solubility but still produced films with low water resistance. It was also noted that, in many cases, the tackiness of a PVP film was increased by plasticizers. Polyvinyl Methyl Ether aud Copolymer The low molecular weight grades of polyvinyl methyl ether pro- duced very sticky solutions with water. Therefore they were not suitable for the preparation of a film-forming concentrate. Polyvinyl methyl ether maleic anhydride copolymers, Gantrez AN©, * have good adhesive properties. However, films prepared with Gantrez AN alone were brittle, and those prepared with plasticizers were tacky and lacked strength sufficient to meet bandage requirements. Acrylic Polymers Acrylic polymers include polyacrylic acid, polymethacrylic acid, their salts, and copolymers of acrylic acid and methacrylic acid with other monomers. One specific feature of these resins is that the vis- cosity of their water solutions is affected by the pH, the degree of ionization of the resins, the kind and amount of counterion, the con- centration of the polymer in solution, and the molecular arrangement of the resins. Rhoplex©$. resins thicken when the pH is increased and produce films which are generally sticky. The excellent strength and water-resistance of the film prepared from acrylic polymers indicate a good prospect for further study of concentrates containing some of these materials. The odors of these materials can be partially masked by the use of various cover odors. Ethylene Oxide Polymers The very high molecular weight (20,000 to 7,000,000) ethylene oxide polymers, Polyox,©$ are a fairly new class of synthetic water-soluble resins. Strong agitation during the preparation of aqueous solutions * Gantrez AN, a product of General Aniline and Film Corporation, New York, N. Y. t Rhoplex, a product of the Rohm and Haas Company, Philadelphia, Pa. :• Polyox, a product of Union Carbide Chemicals Corporation, New York, N.Y.