Silicones, shampoos

Washing removes the natural coating of protective oil that gives hair its body and shine. To counter this, shampoos and conditioners contain hydrophobic oils that cling to the surface of hair and remain in place upon rinsing. Dimethicone, shown in our inset, is an artificial oil that contains hydrophobic silicon-oxygen chains and methyl groups. 

In the category of silicone coatings used for surface modification of the specific substrates, functional silicone fluids are often used, which can selectively interact with the chemical groups of the substrate, thus modifying its surface properties. The use of functional silicones in the textile industry has been discussed in a number of recent publications.5 421 422 The use of different types of high-performace silicone-coated textiles, which include elastomers and resins, has recently been reviewed.423 The use of functional silicones in personal-care products, for example, in shampoos and hair conditioners, mentioned before,381 provides another well-known example. 

The main source of human exposure to cyclic siloxanes is PCPs. Other less significant sources are rubber products, sealants, cookware, silicone grease, pharmaceuticals, medical devices, electronics, dust, and even indoor and outdoor air [277, 281]. The highest concentrations of cyclic siloxanes reported by Lu et al. [282] in PCPs from China were 72.9 pg/g D4 and 1,110 pg/g D5 in shampoos and... 

Synthetic surfactants are commonly used in shampoos, sometimes for reasons of cost and sometimes for performance. Non-ideal mixing in micelles can result when the repulsions between different surfactant head-groups are not uniform, such as when an anionic sulfonate is mixed with a non-ionic ethoxylate or when an anionic is mixed with a betaine. This causes the cmc of the mixture to be smaller than would be the case for ideal mixing, or for either surfactant alone. Such a reduction in cmc can be used to reduce the surfactant monomer concentration in a shampoo. This is an advantage since reducing the monomer concentration reduces the amount of eye and skin irritation experienced when the shampoo is used [904], Other synthetics offer other benefits. For example, some silicone surfactants can not only function as emulsifiers in hair and skin care products, but also act to improve feel, gloss, sheen, emolliency, conditioning and foam stabilization [905]. 

A similar market penetration pattern is seen in hair products (shampoo, coloring products, conditioners, fixatives). Silicones are also used in antiperspirants/deodorants, shaving products, shower and bath oils, gels, and liquid soaps. 

With these properties, saponified polyvinyl acetate-silicone copolymers can be used in cosmetic formulations (e.g., for hair and skin care) such as shampoos, lotions, and cremes or as a fabric care agent. 

The use of silicones in hair care products has increased considerably in the past two decades due to the pleasing aesthetic properties they impart to the hair. They are used in a wide variety of products, including conditioners, shampoos, hairsprays, mousses, and gels [52], The low surface free energy of these materials results in rapid formation upon deposition of a thin, uniform coating on the surface of hair [53],... 

U.S. 5393452 (1995) Raleigh et al. (General Electric) High-molecular-weight, high-viscosity silicone-polyether copolymer Improved antistatic properties conditioning shampoo... 

The primary conditioning agent used in most two-in-one shampoos is dime-thicone. Other related silicones have also been used, either in a primary or secondary capacity, including dimethiconol, amodimethicone, and dimethicone copolyol. Because most of these materials are not soluble in water, two-in-one shampoos are generally oil-in-water emulsions, requiring the use of a suitable stabilizer or emulsifying agent. 

U.S. 4728457 (1988) Fieler (Procter Gamble) Heated premixes (silicone) are added to a main mix (surfactants and suspending agents) at ambient temperature Improved process for making silicone-containing shampoos... 

Silicone products have many commercial roles. At one end of the market, they are crucial ingredients in personal care products silicones are the components of shampoos and conditioners that improve the softness and silkiness of hair, and are also used in shaving foams, toothpastes, anti-perspirants, cosmetics, hair-styling gels and bath oils. At the other end of the spectrum, silicones find very dilferent applications in silicone greases, sealants, varnishes. 

Conditioning agents for shampoos are varied and may generally be classified as lipid-type, soap-type or salts of carboxylic acids, cationic-type including cationic polymers, or silicone-type including dimethicone or... 

Under optimum conditions such as in vivo shampooing, anionic surfactants are nearly as effective as chloroform or ether for removing deposited surface lipid. In most of the tests described in the literature, care was taken to exclude conditioning products, containing cationics and cationic polymers or silicones, setting resins, and hard water to provide more control over the experiments. Obviously these variables must be included before we can arrive at a full understanding and a consensus about the efficiency of anionic shampoos for cleaning hair lipid from the surface of hair. 

---