E57-180 Class H Air-Drying Insulating Varnish for Coils
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Short Product Description：
E57-180 is a Class H, air-drying insulating varnish based on modified heat-resistant polyester resin. Designed for transformer, generator, and motor coils, it combines strong adhesion, flexibility, and wetting performance. This solvent-based varnish supports ambient drying or oven drying and is intended for winding insulation applications requiring a 180°C thermal class.
- Description
- Technical Data
- FAQ
Description
Product Overview:
E57-180 is a heat-resistant electrical insulating varnish developed for the treatment of coils in medium to large electrical equipment. Its modified polyester formulation provides adhesion between winding components and forms a smooth, transparent yellow film after drying.
The varnish helps bond coil assemblies, reducing electromagnetic vibration and associated noise. Its film flexibility helps accommodate differential thermal expansion between metal and insulating materials, limiting stress on the winding structure during temperature changes.
As an air-drying insulating varnish, E57-180 offers an ambient-temperature processing option, with surface drying in ≤20 minutes and through-drying in seven days at 25°C. Oven drying at 110°C provides a faster alternative under the stated test conditions.
E57-180 is identified as Class H, 180°C, in the TDS. It is intended for transformer, generator, electric vehicle motor, and motor stator coil applications. The operating temperature suitability of finished equipment should be verified for the complete insulation system.
Key Features and Benefits：
· Class H Heat Resistance: Designed for winding insulation applications requiring a 180°C thermal class.
· Air-Drying and Oven-Drying Options: Supports ambient drying at 25°C or accelerated drying at 110°C, allowing the process to be selected according to component and production requirements.
· Strong Adhesion: Helps bond transformer and winding components, reducing electromagnetic vibration and associated noise.
· Flexible Insulating Film: Helps accommodate movement caused by temperature changes and differences in thermal expansion between metal and insulating materials.
· Good Wetting Performance: Supports contact with component surfaces during coating and impregnation.
· Electrical Performance After Water Exposure: The TDS reports dielectric strength of 132 kV/mm under normal conditions and 116 kV/mm after 24 hours of water immersion.
· Resistance to Temperature Changes: The TDS describes high- and low-temperature resistance over −40°C to 180°C. Suitability for specific thermal cycling conditions requires application testing.
· Smooth, Transparent Film: Dries to a smooth, transparent yellow coating, allowing the underlying surface to remain visible.
Typical Applications：
E57-180 insulating varnish is intended for coil treatment in medium to large electrical equipment, including:
· Large Transformers: Impregnation and insulation treatment of coil assemblies requiring heat resistance and strong bonding.
· Large Generators: Insulation treatment of generator coils and winding assemblies.
· Electric Vehicle Motors: Treatment of motor coils used in new energy vehicle applications.
· Motor Stator Coils: Winding insulation and bonding for stator assemblies.
· Other High-Temperature Coil Assemblies: Electrical equipment requiring a flexible polyester insulating varnish with Class H heat resistance.
Determine suitability using the actual winding materials, component geometry, electrical requirements, and operating conditions.
Physical Properties：
| Item | Specification | |
| Thermal Class | Class H (180℃) | |
| Properties | Specification | |
| Varnish Properties | Viscosity (25℃, Tu-4 Cup) | 20±5.0 |
| Specific Gravity (25℃) | 0.975±0.03 | |
| Non-Volatile Content (105℃/3h, %) | 46±3.0 | |
| Appearance | Varnish Appearance (25℃, Visual) | Brown translucent liquid |
| Film Color (25℃, Visual) Film State (25℃, Visual) | Yellow, transparent Smooth | |
| Drying Properties | Surface Drying (110℃, min) | ≤5 |
| Internal Drying (110℃, h) | ≤4 | |
| Surface Dry (25℃) | ≤20 min | |
| Full Cure (25℃) | 7 days | |
| Volume Resistivity | Normal State (Ω·m) | 8.5×1013 |
| After 24h Water Immersion (Ω·m) | 2.2×1013 | |
| Dielectric Strength | Normal State (kV/mm) | 132 |
| After 24h Water Immersion (kV/mm) | 116 | |
| Breakdown Voltage | Twisted Pair (TP) Ф=1.0mm AIW (kV) | 16 |
| Film Thickness (mm) | ≥0.05 | |
| Thinner | X-86 series, X-12 series | |
| Shelf Life (at 40℃) | 6 months | |
Technical Notes:
· Viscosity is expressed as cup flow time in seconds.
· Volume resistivity is reported in Ω·m.
· Dielectric strength in kV/mm and twisted-pair breakdown voltage in kV are different test measurements.
· Surface dryness does not indicate complete drying within an impregnated coil.
· Class H thermal classification is distinct from the drying temperature and does not establish a continuous operating rating for every finished assembly.
Application Guidance：
· Preparation and Thinning
Use the specified X-86 series or X-12 series thinner when viscosity adjustment is required. Determine the dilution ratio through trials based on component size, winding structure, and the selected coating or impregnation process.
Verify compatibility with wire enamel, insulation materials, and other assembly components before production use.
· Coating and Impregnation
Apply E57-180 electrical insulating varnish using a coating or impregnation process suited to the component. Establish impregnation time and other operating parameters through trials on the actual assembly.
For large transformers and densely wound components, validate penetration and drying throughout the winding structure before finalizing the production process.
· Reference Drying Conditions
| Drying Method | Temperature | Surface-Dry Time | Through-Dry or Internal Drying Time |
|---|---|---|---|
| Ambient drying | 25°C | ≤20 min | 7 days |
| Oven drying | 110°C | ≤5 min | ≤4 h |
These values are laboratory references. Actual drying time depends on coating thickness, winding geometry, solvent retention, airflow, and component heating.
For oven drying, account for the time required for the component to reach the target temperature. Confirm complete drying before electrical testing or service, particularly for large or densely wound assemblies.
Precautions：
· Determine the dilution ratio, baking temperature, and baking time experimentally based on product shape, size, and specific requirements.
· The product may absorb moisture and turn whitish under high humidity; performance remains unaffected after baking.
· This product is flammable; keep away from fire and heat sources.
Packaging, Storage/Transport & Shelf Life：
· Packaging: metal pails, 18 KG/pail
· Storage & transport: flammable chemical — keep away from fire and heat; handle per regulations; store cool (RT), dark and dry.
· Shelf life: stored sealed, 6 months at 5-25℃.
Frequently Asked Questions About E57-180 Insulating Varnish
1. What is E57-180 insulating varnish used for?
E57-180 is a modified polyester electrical insulating varnish used for coating and impregnation of coils in medium to large electrical equipment. Typical applications include large transformers, generators, electric vehicle motors, and motor stator windings.
It forms a smooth, transparent yellow film that provides electrical insulation and helps bond winding components. Compatibility with wire enamel and other insulation materials should be verified before production use.
2. What is the temperature rating of E57-180?
E57-180 is identified as Class H, 180°C, in the technical data sheet. It is intended for winding insulation applications requiring this thermal class.
The TDS also describes resistance to temperature changes over −40°C to 180°C. Suitability for continuous operation or specific thermal cycling conditions must be validated for the complete insulation system. The Class H rating is separate from the recommended drying temperature.
3. Can E57-180 insulating varnish dry at room temperature?
Yes. E57-180 supports air drying at 25°C, with a specified surface-dry time of no more than 20 minutes and a through-dry time of seven days under the stated laboratory conditions.
Surface dryness does not mean an impregnated coil is fully dry. Actual drying depends on coating thickness, winding geometry, airflow, and retained solvent. Confirm complete drying before electrical testing or service.
4. What are the oven-drying conditions for E57-180?
At 110°C, E57-180 has a specified surface-dry time of no more than five minutes and an internal drying time of no more than four hours under the reported test conditions.
Validate the production schedule on the actual component. Large or densely wound assemblies may require additional time for heating and solvent removal, so oven time alone should not be used to confirm complete drying.
5. How does E57-180 help reduce winding vibration and noise?
E57-180 helps bond winding components, limiting movement associated with electromagnetic vibration and noise. Its flexible insulating film also helps accommodate differences in thermal expansion between metal and insulation materials.
The actual reduction in vibration or noise depends on equipment design, impregnation quality, and operating conditions.
6. What dielectric strength does E57-180 provide?
The E57-180 TDS reports a dielectric strength of 132 kV/mm under normal conditions and 116 kV/mm after 24 hours of water immersion.
It separately reports a twisted-pair breakdown voltage of 16 kV for the specified 1.0 mm AIW wire test. Dielectric strength and twisted-pair breakdown voltage are different measurements; neither should be treated as the allowable operating voltage of finished equipment.
7. Is E57-180 resistant to moisture exposure?
E57-180 retains electrical insulation performance after the stated 24-hour water immersion test. The TDS reports volume resistivity of 8.5 × 10¹³ Ω·m under normal conditions and 2.2 × 10¹³ Ω·m after immersion, with dielectric strength of 116 kV/mm after immersion.
These results apply to the specified test conditions and do not establish suitability for continuous underwater service.
8. Which thinner should be used with E57-180?
Use the specified X-86 series or X-12 series thinner to adjust E57-180’s application viscosity. The supplied varnish has a specified flow time of 20 ± 5 seconds at 25°C, measured with a Tu-4 cup.
Determine the dilution ratio through trials based on component size, winding structure, and the selected coating or impregnation process. Confirm the exact thinner grade and working viscosity before production.
9. What should be checked before impregnating large coils with E57-180?
Check compatibility with wire enamel, insulation materials, and other assembly components. Establish working viscosity, impregnation time, and drying conditions using representative coils.
For large transformers and densely wound assemblies, verify varnish penetration and complete drying throughout the winding structure. Surface coverage alone does not confirm adequate internal impregnation.
10. Why can E57-180 turn whitish during application?
E57-180 may absorb moisture and develop a whitish appearance under high-humidity conditions. The product guidance states that performance is not affected after baking.
Control application humidity and verify the finished coating’s appearance and drying condition. If whitening occurs during an air-drying process, confirm an appropriate corrective drying procedure before accepting the component.
11. What safety and compliance documents are available for E57-180?
Our Insulating Varnish downloads section includes an MSDS, RoHS documentation, and a VOC content test report. Specify E57-180 when requesting documents so the applicable report or declaration and its product coverage can be confirmed.
The Thinners section separately provides RoHS documentation and a halogen content test report. For X-86 or X-12 series thinners, request documents for the exact grade used in your process.
12. How is E57-180 packaged and stored?
E57-180 is supplied in 18 kg metal pails. The stated storage guidance specifies a shelf life of six months when kept sealed at 5–25°C.
Store the varnish in a cool, dark, dry location away from fire and heat sources. E57-180 is flammable; follow the applicable safety data sheet for handling, storage, and transport.
13. What information should I provide when requesting an E57-180 quotation?
Include your equipment type, winding materials, application method, required quantity, delivery destination, and target delivery date. For technical selection, provide the required thermal class and available drying conditions.
If you need trial material or compliance documentation, include these requirements so the applicable documents, packaging, availability, and lead time can be confirmed.