E57-81H Modified Heat-Resistant Unsaturated Polyester Insulating Resin Insulating Varnish
Product Applications:
E57-81H is a one-component, solventless Class H polyester insulating resin formulated with modified heat-resistant unsaturated polyester resin, a high-purity reactive diluent, stabilizers, and functional additives. It is designed for electrical insulation applications that require efficient baking curing and reliable performance under demanding thermal conditions.
The resin offers strong adhesion, good penetration, excellent electrical insulation, and high mechanical strength. It also provides resistance to moisture and mildew, good material compatibility, and reliable resistance to high- and low-temperature thermal shock. Its fast baking-curing performance and easy processing make it suitable for efficient electrical insulation manufacturing processes.
E57-81H is widely used for vacuum impregnation and atmospheric-pressure impregnation of B, F, H, and C insulation-class dry-type power transformers, reactors, EV motors, large generators, hoisting motors, variable-frequency-drive (VFD) motors, and refrigerant-resistant motors.
Typical applications include dry-type transformer insulation, reactor impregnation, motor-winding insulation, electric vehicle motor manufacturing, large-generator insulation, and electrical equipment requiring a solventless, heat-resistant insulating resin.
- Description
- Technical Data
- FAQ
Description
Product Features:
· Eco-friendly modified heat-resistant polyester resin; thermal class: Class H (above 180℃).
· Strong adhesion between transformer components: reduces electromagnetic vibration/noise, cures fast.
· Adjusts metal/insulator expansion coefficient with temperature, reducing coil damage.
· Refrigerant resistant; the film retains good flexibility.
Physical Properties：
The following items are tested in accordance with GB/T15022.2-2017 standard test methods:
| Test Item | Specification |
| Appearance: | Pale yellow to light brown transparent liquid, free of mechanical impurities |
| Viscosity: Ford Cup No.4 viscometer, 23±2℃ (s) | 45±15 |
| Density: (g/cm³) at 25℃ | 1.05±0.03 |
| Gel time: Test tube method, 140±2℃ (min) | 6±3 |
| Thick-layer curing capability: 140±5℃, ≥2h | S₁, U₁, I₂.₁ |
| Dielectric strength: (MV/m)Normal state:After 24h water immersion: |
≥ 22 ≥ 20 |
| Volume resistivity: (Ω·m)Normal state:After 24h water immersion: |
≥ 1×10¹³ ≥ 1×10¹² |
| Refrigerant resistance: 96h | Excellent |
| Storage stability: (Closed cup method) 75±2℃, 24h (no gelation) | Pass |
| (1) The storage life of this product is 6 months. (2) Curing conditions for items 6 and 7: 140±5℃ for 6h. (3) High-purity eco-friendly reactive diluent: X-88. | |
Application Process (for reference, subject to actual customer usage conditions)：
Preparation: The working solution viscosity for general products is between 20-40s; for products with higher requirements, a viscosity of 45±15s is recommended; for small electrical appliances, 12-18s is generally recommended. Under normal conditions, add more than 10% new insulation resin monthly (timing based on actual usage) for long-term continuous use. For long-term continuous use, the insulation resin must be filtered regularly.
Process & Precautions：
| Process | Temperature | Time |
| Workpiece preheating | 110-120℃ | 2-4h |
| Impregnation | 40-50℃ | 15-30min |
| Drip coating | 20-40min | |
| Baking | 145-150℃ | 4-8h (For products with higher requirements, it is recommended to add an additional 2-10h, or bake at 160℃ for 8h) |
Precautions:
· Determine the dilution ratio, baking temperature, and baking time experimentally based on product shape, size, and specific requirements. Recommended baking temperature: do not exceed 100°C.
· 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
What is the minimum order quantity (MOQ) for E57-81H?
The standard MOQ for E57-81H is 18 kg (one pail). For trial quantities below the standard MOQ, please contact us for sample availability and a customized quotation.
What packaging is available?
E57-81H is supplied in the following standard packaging:
- 18 kg per pail
Please contact us for bulk-order pricing, OEM labeling, or customized packaging requirements.
Can I request a sample before placing a bulk order?
Yes. Free samples are available for quality evaluation and application testing. Please contact us to confirm sample availability and quantity. The customer is responsible for shipping costs.
What is E57-81H used for?
E57-81H is a one-component, solventless polyester insulating resin designed for electrical insulation applications. It is widely used for vacuum impregnation and atmospheric-pressure impregnation of dry-type power transformers, reactors, EV motors, large generators, hoisting motors, variable-frequency-drive motors, and compatible electrical windings.
Is E57-81H suitable for vacuum impregnation?
Yes. E57-81H is suitable for compatible vacuum impregnation and atmospheric-pressure impregnation processes. It can be used for transformer windings, reactor coils, motor windings, and other electrical components that require heat-cured insulation treatment.
Does E57-81H require baking?
Yes. E57-81H is a baking-curing insulating resin. Baking conditions should be selected based on resin loading, component size, insulation structure, oven performance, and production requirements.
What are the recommended impregnation and baking parameters?
Recommended viscosity, preheating conditions, vacuum level, impregnation time, draining time, baking temperature, and curing time should be confirmed based on your actual process. Please refer to the Technical Data Sheet (TDS) or contact our technical team for verified application guidance.
Is E57-81H compatible with different insulation materials?
E57-81H is formulated for good material compatibility in electrical insulation applications. However, compatibility testing is recommended before mass production, especially with magnet wire enamel, insulation paper, tapes, bobbins, sleeves, adhesives, and other materials used in the insulation system.
What is the shelf life of E57-81H?
E57-81H has a shelf life of 6 months from the manufacturing date when stored unopened under recommended conditions. Please check the product label or contact us for batch-specific information.
How should E57-81H be stored?
Store E57-81H in a cool, dry, and well-ventilated area away from direct sunlight, moisture, heat, sparks, open flames, and other ignition sources. Keep the pail tightly sealed when not in use. Please refer to the Safety Data Sheet (SDS) for detailed storage and handling instructions.
Does E57-81H meet environmental compliance requirements?
E57-81H complies with applicable RoHS, REACH, and halogen-free requirements. Technical and compliance documents, including TDS, SDS, COA, and available declarations, can be provided upon request.
Do you provide technical support?
Yes. Our technical team can assist with resin selection, vacuum impregnation processes, baking-process optimization, material compatibility testing, and electrical insulation manufacturing requirements.