Gel varnishes

Newton s law states that for a liquid under shear, the shear stress T is proportional to the shear rate. In this sense, most of the unpigmented vehicles used in the paint and printing ink industries are considered ideal or Newtonian liquids. The ratio of the shear stress t to the shear rate D is thus a constant t), dependent only on temperature and pressure. This is not true for specialized gel varnishes and thixotropic systems, which are designed to have special rheological properties. 

Uses Film-former, rheology modifier, leveling agent, antisagging agent for low odor solv.-based paints, thick coatings, textured paints, gel varnishes... 

The presence of the unsaturated substituent along this polyester backbone gives this polymer crosslinking possibilities through a secondary reaction of the double bond. These polymers are used in paints, varnishes, and lacquers, where the ultimate cross-linked product results from the oxidation of the double bond as the coating cures. A cross-linked polyester could also result from reaction (5.J) without the unsaturated carboxylic acid, but the latter would produce a gel in which the entire reaction mass solidified and is not as well suited to coatings applications as the polymer that crosslinks upon drying. ... 

The ether is also used in paint, varnish and lacquer formulations. A recent development is the use of ethyl cellulose gel lacquers. These are permanent coatings applied in a similar way to the strippable coatings. They have been used in the United States for coating tool handles, door knobs and bowling pins. 

Liquid crystals are mainly used for decorative purposes in cosmetics. Cholesteric liquid crystals are particularly suitable because of their iridescent color effects, and find applications in nail varnish, eye shadow, and lipsticks. The structure of these thermotropic liquid crystals changes as a result of body temperature, resulting in the desired color effect. In recent times, such thermotropic cholesteric liquid crystals have been included in body care cosmetics, where they are dispersed in a hydrogel. Depending whether this dispersion requires stirring or a special spraying process, the iridescent liquid crystalline particles are distributed statistically in the gel (Estee Lau-... 

The use of high-concentration gels and varnishes has been practised clinically for many years by dentists and dental hygienists [180]. When originally formulated, they were designed to be used in application procedures based on the concept that fluoride becomes incorporated into the crystalline phase of the enamel and leads to the development of a more acid-resistant form of apatite. They were not expected to make any difference to the levels of fluoride in saliva, or to influence the demineralisation/dissolution phase of the behaviour of tooth mineral. 

Fluoride-containing varnishes are designed to be painted onto the teeth and retained for a few hours at least, during which they release fluoride close to the tooth surface [188], Like fluoride gels, they are intended for use by dental professionals, but have the advantage that they are considered to be easy to apply. They have an acceptable taste and contain lower amounts of fluoride than gels. They contain either sodium fluoride or difluorosilane as the active ingredient. 

Fluoride varnishes have, though, been shown to be effective in preventing caries in children [190,191]. Applied at six month intervals, these varnishes were found to be as effective as fluoride gel [191]. Some reports conclude that more frequent applications are desirable, for example, four times a year and there is also some evidence that three applications within a week, at yearly intervals might be beneficial [192,193]. However, overall the evidence is inconclusive. 

The overall mode of action of fluoride varnishes is the same as gels, namely that they deposit soluble fluoride as calcium fluoride. When local pH adjacent to this deposit falls, fluoride is solubilised and then proceeds to become incorporated into the tooth mineral as fluorapatite [196]. 

L. Seppa, T. Leppanen, H. Hausen, Fluoride varnish versus acidulated phosphate fluoride gel A 3-year clinical trial. Caries Res. 29 (1995) 327-330. 

The final purification of the varnish from mechanical impurities and gel takes place in the ultracentrifuge, from where the purified varnish is pumped into container 22. 

The dosage forms of topical fluoride currently available include varnishes, dentifrices, solutions, gels, mouthwashes, and prophylaxis pastes. These various forms are outlined in Table 3. 

A number of studies have reported that topical fluoride application may reduce dental hypersensitivityJ ° These results have been found when concentrated dosage forms have been applied ranging from 8% stannous fluoride gels to 33.3% sodium fluoride paste. It has been shown that commercial dentifrices containing stannous fluoride may also decrease dental hypersensitivity. Also, a combination of stannous fluoride and potassium nitrate is marketed by one manufacturer to reduce sensitivity. Varnishes containing sodium fluoride have also been shown to reduce dental hypersensitivity. 

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. 

Chem. Descrip. Modified fluoroalkyl siloxane, water-based Uses Surf, modifier for oxidic, carboxy- and hydroxytunctional substrates (e.g., ceramics, metals, nat. fibers like cotton or wood) corrosion inhibitor for metal surfs. additive for sol-gel systems antitouling finish for marine hulls modifier for paints, varnishes antigraffiti coatings tor min. and metallic surfs. adhesion promoter for fluoropolymers (paints/coatings, lubricants) mfg. of nonstick cookware water- and oil repellent for textiles fluoro modifier for polymers... 

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