Архивы рубрики ‘Understanding. Coatings Raw Materials’

Radical scavengers

UV absorbers do not protect the surface of coatings, and therefore, they are often supplemented by another type of light stabilizers called radical scavengers. In contrast to UV absorbers, radical scavengers act at the coating’s surface as well as in bulk, and act only when free radicals are generated. They are based on ste — […]

UV absorbers

UV absorbers (Figure 5.20) are organic compounds that absorb harmful UV light and dissipate the absorbed energy as harmless thermal energy. Important classes of UV absorbers are 2-hydro — xybenzophenones, benzotriazoles, hydroxyphenyl-s-triazines, and oxalanilides. Some other compounds such as hydroxyphenylpyrimi — dines, salicylic acid derivatives and cyano acrylates are also useful. The key to effectiveness […]

Light stabilizers

Coatings for exterior applications, such as automotive coatings, are subjected to severe weathering, causing degradation of coating binders. The primary damaging components of weather are light (especially UV radiation) and oxygen, though other factors such as moisture, fluctuations in temperature and acid rain also influence damage to some degree. UV radiation has sufficiently high energy […]

Types of anti-skinning agents

Two important classes of anti-skinning agents used in the coating industry are phenols and oximes (Figure 5.19). Phenols Sterically hindered phenol derivatives are commonly used as anti­skinning agents because of their powerful antioxidant action, causing considerable loss-of-dry. Typical examples are butylated hydroxytoluene (BHT), and o-isopropyl phenol (Figure 5.19). They act as anti-skinning agents by […]

Anti-skinning agents

Skinning is the formation of a film on the surface of a liquid coa­ting containing oxidatively curing binder as a result of its reaction with the oxygen in the headspace in a can. It is particularly noticea­ble in partially filled cans. Skinning is an undesirable phenomenon because it results in material losses, delayed painting process […]

Coalescing agents

Latex-type binders account for a large volume of waterbased coa­tings. Film formation in a latex paint involves the coalescence or fusion of discrete polymer particles of high MW polymers. When the film is applied, the polymer particles are pushed against each other under the capillary forces generated due to progressive evaporation of water. This results […]


UV curing is an environmentally friendly coating technology in which binder is cured on exposure to UV radiation via either free — radical copolymerization or cationic polymerization. The vehicles of UV-cured coatings contain oligomeric resins and reactive dilu­ents. The main resin types for such coatings are radically poly­merizable unsaturated polyesters and acrylates or methacrylate terminated […]

Acid catalysts for baking systems

One-component baking types of coatings in which resins such as alkyd, polyester, hydroxyl func­tional acrylic or epoxy esters are cross-linked with amino resins are typically catalyzed by acid catalysts. Strong acid catalysts such as sulfonic acid and phos- Figure 5.14: Acid catalysts for amino-cured backing systems phoric acid are generally used. Even though less reactive […]

Catalysts for epoxy system

Epoxy resin cross-linked with an amine functional resin is also an important coating system used in high-performance applications. Catalysts used for such systems have been either acidic compounds bearing phenolic hydroxyl groups or a tertiary amine. One of the most commonly used catalysts for two-component epoxy systems is tris(dimethylamino)phenol (Figure 5.13). Epoxy/carboxy/acid anhydride systems are […]

Catalysts for polyurethane coatings

Polyurethane coatings, one of the most important coating systems among the modern high performance coatings, are two-compo­nent systems based on polyols and isocyanates. Curing occurs at ambient temperature. Aliphatic polyisocyanate-based systems react more slowly than aromatic ones, and therefore, they need to be catalyzed. The catalysts used for polyurethane systems can be broadly categorized as […]