Enamels are most prominently associated with copper and aluminum magnet wire. These smooth, thin insulators minimize space consumed in wound coils, have high dielectric strength, and may provide moisture and solvent resistance.
The enameling process involves applying a resin enamel to a bare wire and forming a hard insulating layer through a heating and curing process.
During the enameling process, the wire is passed through an enameling tower several times and cured to increase the thickness and durability of the coating.
The overall increase in wire diameter attributable to the layers of enamel is called the build. Build specifications may be described as “single”, “heavy,” and “triple”. A heavy build is twice the thickness of a single build, and a triple build is three times the thickness of a single build.
Facilities for enameling are called enameling “towers”（or enameling dies） because of the vertical layout of drying and curing operations. Enameling towers may be in tandem with drawing, annealing, and cleaning operations.
Types of Enamels
Enamels may be used in combination, and numerous variations exist. A brief listing follows:
Plain enamel. Synthetic resins and modifying agents. Applications include transformers and telephone coils.
Nylon. A tough thermoplastic that may be removed by molten solder. Applications include automotive electrical devices.
Polyurethane. Formed by reacting a form of isocyanate and a polyester. It may be removed with molten solder. Used in fine wire applications Polyvinyl formal (Formvar).
Classical enamel. Involves a reaction with phenol-formaldehyde and possibly with isocyanate and melamine. Requires stress relief. Is still used where resistance to oil may be required.
Solderable acrylic. Water dispersion of acrylonitrile polymer, acrylic acid, and butyl acrylate is applied. It may be removed by molten solder. Applications include automotive electrical devices.
Epoxy. Early resin solution coatings had properties similar to those of polyvinyl formal. Powder coating technologies have subsequently become available. Provides good resistance to oil-containing media.
Polyester. This enamel is from the terephthalic acid category. Good heat and heat shock resistance. Used in a variety of electrical and electrical coil products.
Polyimide. Involves the reaction of pyromellitic dianhydride with an aromatic diamine. Very high thermal stability and overload resistance. Resistant to solvents and acids but not to alkalis. Used in high-performance electrical devices.
Polyester-polyamide-imide. The base is a modified polyester with an overcoat of amide-imide polymer. Superior properties and wide general application.
Enameled wires and the enameling process play a vital role in the insulating properties and durability of wires, and proper enameling techniques can significantly improve the service life and reliability of wires.
For 3Better’s enamel dies, read Products – Enamel dies. Or contact us.
