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j. Soc. Cosmet. Chem., 43, 275-284 (September/October 1992) Silicones as conditioning agents in shampoos KAZUYUKI YAHAGI, Tokyo Research Laboratories, Kao Corporation, 2-1-3 Bunka, Sumida-ku, Tokyo 131, Japan. Received April 29, 1992. Presented at the XXIII CED Meeting on Surfactants, Barcelona, March 11-13, 1992. Synopsis A one-step shampoo, generally called a "2 in 1" shampoo, exerting both cleansing and conditioning functions, differs to a great degree from conventional shampoo products, with its superb conditioning effects eliminating the necessity of a further conditioning step. Conditioning agents especially effective in such types of products are silicones, especially dimethicones with high molecular weight, dimethicone copolyol with low hydrophilic-lipophilic balance (HLB), and amodimethicone. In this work, the condi- tioning effects of these silicones are discussed in terms of the surface deposition and alteration in hair surface characteristics by measuring the kinetic frictional coefficient of hair fibers in relation to the chemical types and the molecular weight of silicones. The improvement in surface kinetic characteristics was primarily noted with dimethicones with high molecular weight. Dimethicone copolyol with low HLB lowered the kinetic friction of the wet hair surface by forming liquid crystals. Amodimethicone improved manageability of hair by adsorbing strongly onto the damaged, and therefore more polarized, hair cuticles, which facilitated hair styling without blow-drying. INTRODUCTION The use of silicones as lubricating and hydrophobic agents is found in a number of hair care products, e.g., shampoos, rinse conditioners, conditioners, hair sprays, styling mousses, setting lotions, hair colorings, permanent wave solutions, etc. Ease in comb- ing, as well as a soft and smooth feeling without greasiness is the most valuable benefit obtained with silicones in hair care products. Another important factor is that silicones are non-toxic and non-irritating, and essentially safe. In the present day, approximately 40% of Japanese females wash their hair daily with younger generations this figure rises to approximately 70%. Therefore, a one-step shampoo, generally called a "2 in 1" shampoo, with double functions of shampoo and conditioner, is highly beneficial to these users for its ease and convenience. While its foaming and cleansing performance is comparable to an ordinary conditioning shampoo, the conditioning effect of a "2 in 1" shampoo is far greater than that of an ordinary conditioning shampoo. The groups of conditioning agents utilized in a "2 in 1" sham- poo include silicones, hydrocarbon oils, fatty alcohols, cationic polymers, and cationic surfactants. There are some types of silicones that are especially effective as conditioners in detergent systems. 275