Лако-красочные материалы — производство

Table 3.4: Complex inorganic color pigments Pigment (CI name) Metal composition Color Crystal structure Titanate pigments Pigment Yellow 53 Ni, Sb, Ti Lemon yellow Rutile Pigment Brown 24 Cr, Sb, Ti Yellow-orange Rutile Pigment Green 50 Co, Ti Bluish-green Spinel Aluminate pigments Pigment Blue 28 Co, Al Blue Spinel Pigment Blue 36 Co, Cr, Al […]

While weather fastness may be evaluated by exposing the sample to actual outdoor conditions for a prolonged time, accelerated tests are more commonly used in industry. In an accelerated weathering test, the specimens are exposed to cycles of different atmospheric factors such as light, dark, water spray, temperature change and varying humidity in a specific […]

When pigmented coatings are used in outdoor conditions, light is not the only factor affecting film degradation. A range of other factors such as heat, moisture, rain, fumes and other industrial gases are responsible, to more or less of an extent, for performance of the coating. Weather fastness is the ability of a pigment-binder system […]

Many pigmented coatings are required to retain their original color when they are exposed to daylight during their service life. Light fastness is a pigment’s resistance to discoloration when exposed to daylight. Of the total radiation of daylight, UV is the most damaging portion, though it is not the only responsible factor. Light fastness is […]

Oxidative polymerization of drying oil-based polymers is the most com­mon mechanism of film formation. During the initial period of drying, the pigment is in a highly oxidizing environment due to the presence of free radicals, hydro-peroxides and activated catalysts. This environ­ment becomes more severe with force-dried finishes that may be baked at elevated temperatures. The […]

Pigments such as white lead and zinc oxide react with free acids in paints and coatings to respectively form lead and zinc soaps of the acids. Titanium dioxide and many other extender pigments are non-reactive and do not form soaps. Lead and zinc soaps have low solubility in the vehicle and tend to increase the […]

One of the important characteristics of a pigment is its inertness to chemicals it may come in contact with. These chemicals may be paint ingredients or others that come in contact with the coating film. Resins, cross-linkers or certain additives may show reactivity toward a pig­ment, causing noticeable change in its performance. The chemicals that […]

3.1.1.4 Chemical purity Most synthetic pigments produced by industry are pure chemical compounds, but natural inorganic pigments are processed minerals. The impurities in natural pigments may vary significantly from source to source. Even though physical appearance and some phy­sical properties are similar, the presence of some chemical impurity may impair the performance of the final […]

Oil absorption value has been used as an important specification for pigments and is very useful to coating formulators. Oil absorp­tion value is defined as the minimum amount (in g) of linseed oil required to wet 100 gm of pigment to form a coherent paste. To perform an oil absorption test, linseed oil is added […]

The ease of dispersion of pigments can be tested by dispersing a pigment in a given paint medium in an oscillatory shaking machine (for low viscosity medium) or automatic muller (for high viscosity medium). The time (in case of an oscillatory shaking machine) or the number of cycles at constant pressure (for an automatic muller) […]