Shop - E57-81H Class H Solventless Polyester Insulating Varnish for Motors & Transformers

Description

Product Overview：

E57-81H is a heat-curing electrical insulating varnish made with modified unsaturated polyester resin, high-purity X-88 reactive diluent, stabilizers and additives.

Developed for winding impregnation, E57-81H penetrates assemblies and forms a bonded insulating structure after curing. Strong adhesion between winding and insulation components helps reduce electromagnetic vibration and associated noise, while cured-film flexibility helps accommodate differential thermal expansion between metal and insulating materials.

This polyester insulating varnish also offers moisture resistance, mold resistance, refrigerant resistance, and resistance to thermal shock. Its single-component formulation simplifies preparation for vacuum and atmospheric impregnation processes used in electrical equipment manufacturing.

E57-81H provides Class H heat resistance at 180°C for electrical winding insulation.

Key Features and Benefits：

  · Class H Heat Resistance: Designed for winding insulation applications requiring elevated-temperature performance.

  · Single-Component Formulation: Simplifies preparation without a separate two-component resin and hardener mixing step.

  · High-Purity Reactive Diluent: Use X-88 reactive diluent to adjust the viscosity of E57-81H.

  · Strong Adhesion and Mechanical Reinforcement: Helps secure winding components and reduce electromagnetic vibration and associated noise.

  · Good Impregnation Performance: Supports penetration into winding assemblies through vacuum and atmospheric impregnation.

  · Electrical Performance After Water Exposure: Specified dielectric strength is ≥22 MV/m under normal conditions and ≥20 MV/m after 24 hours of water immersion.

  · Moisture and Mold Resistance: Supports applications where resistance to humidity and mold is an important insulation requirement.

  · Thermal Shock Resistance: A degree of cured-film flexibility helps accommodate movement caused by temperature changes and differences in material expansion.

  · Refrigerant Resistance: Provides excellent refrigerant resistance in a 96-hour test. Check compatibility with the refrigerant used in your application.

  · Heat-Activated Curing: A specified gel time of 6 ± 3 minutes at 140 ± 2°C supports process characterization. Full curing requires the appropriate baking cycle.

Typical Applications：

E57-81H insulating varnish is intended for vacuum and atmospheric impregnation of:

  · Dry-Type Power Transformers: Winding insulation and bonding of transformer components.

  · Electrical Reactors: Coil impregnation requiring electrical insulation and mechanical support.

  · Electric Vehicle Motors: Insulation treatment of motor windings used in new energy vehicles.

  · Large Generators: Impregnation of generator winding assemblies.

  · Hoisting and Crane Motors: Winding insulation for motors used in lifting equipment.

  · Inverter-Duty Motors: Impregnation of windings in variable-frequency motor systems.

  · Refrigerant-Resistant Motors and Electrical Equipment: Applications requiring compatibility with the intended refrigerant environment.

Validate compatibility with wire enamel, insulation materials, and other assembly components before production use.

Physical Properties：

E57-81H’s physical, processing and electrical properties are listed below, with test methods referencing GB/T 15022.2-2017.

Technical Notes:

  · Specimens for dielectric strength and volume resistivity testing were cured at 140 ± 5°C for 6 hours.

  · Viscosity is expressed as cup flow time in seconds, not dynamic viscosity in mPa·s.

  · Volume resistivity is reported in Ω·m.

Application Guidance：

  · Working Viscosity

Select the working viscosity according to component size, winding structure, and impregnation requirements. Recommended reference ranges:

Confirm measurement conditions and the viscosity adjustment procedure with our technical team. Use the specified X-88 reactive diluent according to our TDS instructions.

  · Reference Impregnation and Curing Process

For applications with higher performance requirements, recommends extending the baking time by 2–10 hours or using an alternative schedule of 160°C for 8 hours.

These parameters are starting points for process development. Validate the cycle using the actual component geometry, thermal mass, impregnation equipment, and required insulation performance.

Laboratory gel time must not be used as the full curing time. Confirm complete curing throughout the winding assembly before electrical testing or service.

  · Impregnation Bath Maintenance

For continuous operation, recommends adding more than 10% fresh insulating resin approximately monthly, with the interval adjusted to actual use. Confirm the replenishment basis with our technical team.

Filter the resin regularly during prolonged use and monitor its condition to maintain a consistent impregnation process.

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.

Packaging, Storage/Transport & Shelf Life：

  · Packaging：

20 KG/pail; 200 KG/drum.

  · Storage and Transportation：

Keep away from ignition sources and heat. Handle and transport in accordance with applicable regulations.

Protect the varnish from sunlight and ultraviolet light during storage and use. Store in a cool, well-ventilated area below 40°C.

During use, avoid leaving the product sealed and undisturbed for prolonged periods. Gentle circulation or stirring helps extend storage life.

Viscosity may increase slightly during storage. Before use, adjust to the required application viscosity with the designated thinner.

  · Shelf Life：

Six months when stored in sealed containers at temperatures below 40°C.

Please Note：

  · As our products are continuously improved, the information in this manual may be updated from time to time without prior notice. Please feel free to contact our sales team for the latest version.

  · Do not mix this product with other products.

  · We strictly control product quality and supply products in accordance with applicable product standards. Custom products are supplied according to mutually agreed specifications. Application conditions vary and are beyond our control. You should therefore test and evaluate the product and the information provided in this manual, together with the recommended application procedures, to determine suitability for your specific use.