lacquers based on the products of polymerization of esters of acrylic or methacrylic acid (acrylates).
Acrylic lacquers are divided into two groups, depending on the type of film-forming material: (1) materials made from macromolecular thermoplastic polyacrylates—for example, copolymers of methyl methacrylate and butyl acrylate; and (2) materials made from thermosetting oligomers—for example, copolymers of acrylates with styrene and acrylamide.
Lacquers of the first group form reversible (soluble) coatings as a result of evaporation of the solvents (the time required for film formation at room temperature is about 1 hr), whereas lacquers of the second group form irreversible (insoluble) coatings in 30-40 min at 125°-150°C as a result of reactions of the functional groups of the film-forming material. Solvents for acrylic lacquers are mixtures of esters (most frequently acetates), ketones, and aromatic hydrocarbons; the thermosetting film-forming materials are soluble in water. Plasticizers such as phthalates and sebacates are sometimes added. Spraying is mainly used to apply acrylic lacquers and other pigmented materials based on them, such as prime coats, enamel paints, or polyacrylic enamels; the water-soluble materials are applied by electrodeposition.
The advantages of acrylic lacquers are good adhesion to metals and resistance to light, air, and water. Their disadvantage is relatively high vapor permeability. The temperature limits for their use are from—50° to 150°-170°C (reversible coatings tend to soften at high temperatures). Lacquers made with thermoplastic film-forming materials are used mainly for anticorrosion protection of aluminum and aluminum alloys, whereas enamels are used for painting various metal structures and to produce shiny coatings on store windows and display stands. Enamels made with thermosetting oligomers are mainly used for painting automobiles, motorcycles, instruments, and medical equipment.
REFERENCEEntsiklopediia polimerov, vol. 2. Moscow, 1974.
See also References under VARNISHES.
M. M. GOL’DBERG