J. Soc. Cosmet. Chem., 22, 179-186 (March 4, 1971) Reactions of Metal Salts Human Hair Containing Synthetic Polymer with GIUSEPPE ANZUINO, Ph.D.,* and CLARENCE ROBBINS, Ph.D.* Synopsis--Human HAIR FIBERS containing synthetic POLYMER with functional groups capable of acting as donor groups in coordination complexes were reacted with METAL SALTS (acceptor groups) and examined for changes in the wet load exter•sion properties. Mercury(II), a particularly effective "acceptor group" in this system, was found to produce cxtremely large increases in the wet load EXTENSION PROPERTIES of hair fibers con- taining either a tertiary amine polymer, an alcohol polymer, or a nitrile polymer. INTRODUCTION Harris and Brown (1) in 1946 showed that the disulfide bonds of wool fibers play an important role in the wet strength properties which increase almost linearly with the cystine content. Evidence for their contribution was obtained by reducing and methylating wool fibers to different extents and determining both the wet and dry load extension properties. This work also showed that the dry strength of wool fiber, through 30% extension, is not appreciably affected through a 60% de- crease in the cystine content. In 1951, Alexander et al. (2) indicated similar results from the oxidation of wool fiber with peracetic acid. Re- lated results have been obtained in our laboratories for hair fibers that have been bleached with home commercial bleaching products (3). Since the wet tensile properties of human hair are adversely affected by two frequently used chemical treatments [permanent waving (reduc- * Chatilion S.p.A., Largo Chatilion, Vercelli, Italy. ? Colgate-Palmolive Research Center, 909 River Road, Piscataway, N.J. 08854. This work was conducted at the Colgate-Palmolive Research Center where all correspondence should be addressed. 179

180 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS tion-oxidation) and bleaching (oxidation)], and since the wet tensile properties are altered more by these treatments than the dry properties, the objective selected was to explore means for increasing the wet load extension properties of keratin fibers through mild conditions (room temperature, aqueous media, and short reaction times) of reaction. Our approach involved polymerizing vinyl monomers within the kera- tin fibers (4-8) to alter their chemical reactivity (9) and subsequently reacting the polymer-containing fibers with metal salts. It was believed that these reactions might increase the cross-link density and/or decrease the saturation water content of the fibers, methods which have been suggested (10) to be effective for increasing the wet load extension properties of wool fibers containing no synthetic polymer. EXPERIMENTAL The keratin fibers used in this investigation were frown brown Cau- casian human hair.* The monomers were purified in the usual manner followed by distillation. Other chemicals were of reagent grade or of the highest purity available. For polymerizing in hair, single fibers were immersed in 20 ml of 6% ammonium thioglycolate (pH • 9) for 3 rain, washed with deionized water, and then immersed in 20 ml of water-alcohol mixtures of vinyl monomer (10,%) and cumene hydroperoxide (4%) for 60 rain at room temperature. Enough alcohol was added to the system to completely solubilize the hydroperoxide and/or monomer. The amount of poly- mer within the fibers was estimated by weight pickup as determined at 55% RH. Treatment with metals involved immersion of fibers in metal salt solutions at times and concentrations indicated in the text. Unless stated otherwise, the following procedure was used for de- termining the changes to the stress-strain properties of the fibers. After being mounted 5 cm apart on tabs, the fibers were placed in deionized water at 24øC for at least 1 hour and stretched to 20% of their initial length on an Instron tensile tester,* at a rate of extension of 0.25 cm/min. The fibers were then relaxed in water, overnight, dried at room tempera- ture, and treated and stretched again under the same conditions. In this manner, before and after measurements were made on 3 to 10 fibers per treatment. Changes in the mechanical properties are expressed as the percentage change in the work to 20% extension (WE), the elastic * Purchased from De Meo Brothers, New York, N.Y. * Instron Corporation, 2500 Washington St., Canton, Mass. 02021.