Лако-красочные материалы — производство

A variety of the organic solvents used in coatings can be broadly classified by their chemical type into the following three categories: Hydrocarbon solvents, which are organic compounds comprised of molecules consisting only of hydrogen and carbon atoms. Oxygenated solvents, which are organic compounds comprised of molecules consisting of hydrogen, carbon and oxygen atoms. Other […]

Electrical resistivity is a critical parameter of coatings, particularly those that are applied by an electrostatic spray or bell applicator, as it influences the transfer efficiency and coating appearance. There­fore, the electrical resistivity of paint must be properly adjusted and is mainly accomplished by selection of appropriate solvents. Non­polar solvents, such as hydrocarbons, have high […]

Refractive index is a characteristic property of solvents and is very sensitive to the composition of solvent blends. Therefore, it is use- Table 4.2: Properties of some important representative solvents Solvent BP [°C] ST [dyne/cm] Density [g/ml] at 20 °C ER FP [°C] Hydrocarbon solvents Mineral spirits (low aromatic) 182-190 26 0.79 200 63 Solvesso […]

Most solvents are clear and colorless. If a solvent exhibits some color, it may be an indication of the presence of impurities or conta­mination that might have occurred during storage and distribution. Therefore, color is often an important specification requirement to judge the quality of the solvent.

Density, a fundamental physical property, is an important conside­ration, as it can have a major effect on cost. In most cases, solvents are sold on a weight basis, but coatings are sold on a volume basis. In addition, the solvent is generally the lightest ingredient of the coating; therefore, density of the solvent is important […]

Flash point is one important indicator of the relative flammabi­lity hazard of solvents and solvent-containing products; therefore, this is a very important specification for solvents and paints. The flash point of a liquid may be defined as the lowest temperature at which the liquid, in contact with air, is ignited by a spark or flame […]

The temperature at which the vapor pressure of a liquid is equal to the atmospheric pressure is known as its boiling point. This is a characteristic property of pure solvents and is often used in specifications for solvents. When a solvent consists of a mixture of components, such as most hydrocarbon solvents, boiling occurs over […]

4.1.1.3 Surface tension Surface tension of liquid paint is an important characteristic that influences a number of properties of the final coating. A liquid can wet a surface only when its surface tension is lower than the sur­face free energy of the surface. Solvents play a very important role in controlling the surface tension of […]

Although solvency and evaporation rate are the most important properties, there are other properties that are important in specific circumstances. Some of them are briefly discussed here. 4.1.1.1 Moisture content The presence of any appreciable amount of moisture in solvents used in a two-component polyurethane system can react with iso­cyanate crosslinkers and thus impair crosslinking […]

While the solvency of solvents is important in dissolving resins and controlling paint viscosity for ease of application, their evaporation rate is equally important, as a solvent must leave the coating film by evaporation at a controlled rate in order to give a uniform and defect-free dry film. Selection of solvents is important in controlling […]