Film-forming auxiliaries

Auxiliary solvents and film-forming auxiliaries are also used as flow promoting agents in aqueous dispersions (emulsion paints). Propylene glycol acts not only as a solvent, but is hygroscopic and thus ensures a sufficiently high water content in the coating until a smooth surface has formed. 

Butyl diglycol acetate [124-17-4] [2-(2-butoxyethoxy)ethyl acetate] is a high boiler that is used as a temporary plasticizer, as a leveling agent in stoving enamels and in printing inks, as a film-forming auxiliary in acrylate copolymer dispersions, and to reduce the viscosity of poly(vinyl chloride) plastisols. 

Propylene carbonate [ 108-32-7] is liquid at room temperature. It is a high boiler with a solvency resembling that of ethylene carbonate. It dissolves polyacrylonitrile only in combination with ethylene carbonate. Propylene carbonate is used in paints as a high-boiling solvent and film-forming auxiliary, especially in polyfvinyl fluoride) and poly(vinylidene fluoride) systems. It is also employed as an auxiliary in the pigment and dye industry. 

In a normal atmospheric exposure, a Iresh lead surface will slowly be oxidized into a thin, protective lead oxide, which halts further oxidation of the metal. The rate of formation of lead oxide is determined by the absorption of oxygen and water vapor into the lead. Such factors as industrial and marine pollution, humidity, temperature, and rainfall profoundly affect the aggressiveness of the atmosphere, and most metals suffer accordingly. However, the protective films formed of lead are so effective that corrosion is insignificant in most natural atmospheres. The extent of this protection is demonstrated by the survival of lead roofing and auxiliary products after hundreds of years of atmospheric exposure that may continue for a much longer time if these films are not damaged [2]. 

Natural macromolecular materials, which form multimolecular films around the disperse droplets of O/W emulsions. They are frequently called auxiliary emulsifying agents and have the desirable effect of increasing the viscosity of the dispersion medium. However, they often suffer from the disadvantages of being subject to hydrolysis and sensitive to variations in pH. 

When processing auxiliaries such as copovidone in formulations for solid dosage forms, the particle size distribution can be of considerable importance. This particularly applies to the manufacture of tablets. However, it can also be important in solutions, e.g. film-coating solutions for tablets, as the dissolution rate and the dusting properties depend on the proportions of coarse and fine particles respectively. 

Auxiliaries. Dispersants ensure that the individual particles in the emulsion paint do not combine to form agglomerates. Protective colloids and emulsifiers are used during emulsion polymerization to ensure that small polymer spheres are formed in the aqueous phase but do not fuse together. They influence film formation of the emulsion paint and can cause foaming. Protective colloids include polyfvinyl alcohols) and cellulose ethers. Emulsifiers include anionic and nonionic surfactants. 

The basic chemicals for coatings are polymers which form a film or crosslink on the fibre or fabric, together with additives and auxiliaries. Additives may be pigments for colour or for the reflection of UV or IR radiation. In the future, it will become possible to apply the filler as nanoparticles, thus creating a new class of properties. 

A modem calender is used to form a film or a sheet. Compounding operations are performed on auxiliary equipment which may be more complex than the calender itself Formulation and a repeatable compounding method frequently determine the quality of the calendered product. 

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