In order to improve the characteristics of lacquers and enamels of air drying, as well as to accelerate curing drying them sometimes carried out at elevated temperatures (40-60 C). Main of lacquers have the following features. Oil varnishes form (after drying), flexible elastic film of yellow color, resistant to moisture and mineral oil. On heat resistance of the film of varnish are in class A (up to 105 C). Since the oil varnishes are used in short supply (linseed and tung) oil, then their use is limited and they are replaced by synthetic resins for lacquers, more resistant to thermal aging. Bitumen-oil varnishes form a flexible film in black, resistant to moisture, but is easily soluble in mineral oil (transformer and lubricating). Because of the high availability and good insulating properties of bitumen-oil varnishes widely used in electrical engineering.
For heat resistance, these coatings are in class A insulation (105 C). Alkyd (glyptal) and oil-glyptal varnishes and enamels have good bonding strength with respect to the mica paper, cloth and some plastics. The films of these paints have a high thermal stability (class B). They are resistant to the heated mineral oil, but require a hot (oven) drying at temperatures of 105-150 C. Pure glyptal Coatings based on unmodified glyph Traveling resins form hard rigid film (paint number 1155 and others) used in the manufacture of hard mica insulation (solid Micanites). Gliftale-oil varnish form a flexible film dark yellow. Alkyd-melamine varnish – varnish is a composite consisting of 84% oil-varnish glyptal number 1154 and 16% of the melamine-formaldehyde resin, introduced to improve the water resistance and shorten the curing varnish. Organosilicon varnishes and enamels have high heat resistance and can operate continuously at 180-200 C (Temperature class NICs) so they are used in combination with glass fiber and mica insulation. Films These lacquers and enamels have high electrical characteristics, which vary little in the aging process.