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Sunday, 13 October 2019

Properties and Applications of Varnishes and Enamels

Some of the properties and application of Insulating varnishes and enamels are given in Table.

Properties and Applications of Varnishes and Enamels

Curing schedule
Thermal class
Gleoresinous varnishes
8 - 12 Hrs E (120°C) at 90°C -120°C
E (120°C)
Flexible, good bonding properties, resistance to humidity acid, alkali
Impregnating varnish suitable for explosion proof encloses & repair purposes.
synthetic resin varnish
10- 12 Hr 120°C or 8.9 Hrs. 130°C
B (130°C)
- do -
good penetration, low drainage loss.
Impregnating varnish for application of transformers, enamel wires, and explosion proof enclosures.
less varnish
16 Hrs
at 120°C
B (130°C)
High viscosity
curing well in depth giving good bonding & flexible cured mass.
- do -
stator, rotors transformers & for additional moisture protection. All types of electrical equipments.
Glass fibre varnishes
Air drying
B - F (145°C to 150°C)
The film of varnish fixes the glass fibres without deteriorating the suitability of tape.
Impregnation of glass tapes.
Silicon varnish
12 to 16 hrs at 180°C
F & H
155°C continued
operation very good at electrical proper-ties strength, good flexibility humidity resistance.
Situation of humid
atmosphere, fractional motors, marine equipment, explosion proof enclosures Impregnation of glass covered wires.
R.C. varnish
20 min. at 130°C
Good resistance to moisture, acid & alkalies.
Protective coating for resistors and electronic components.
Core plate varnish
250°C -300°C by infrared heating (45 - 50 secs)
Resistance to punching operation & pressure.
Coating for electrical sheet steel
Stripping Lacquer
1 Hr. Air drying
Easily removable after stoving
Coating of parts where impregna-tion with varnish is not desired
Cures during prebake for equipment
Turns brittle under action of heat
Protection of bare machine parts e.g., shafts housing racers etc., before applying impregnating varnish
Conducting varnish
Air drying 15 minutes
Good electrical conductivity.
For screening purpose in high frequencies & tele communication engg. In high voltage machines for stress grading purposes
Insulating cement varnish
80 to 120°C for about 1 Hour
Excellent adhesive power and retension of adhesion with backing, transparent
Cementing varnish for all purpose in electrical insulation for bonding coil formers, press board etc., used in large size transformers

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