E57-81 Modified Heat-Resistant Unsaturated Polyester Insulating Resin Insulating Varnish
Product Applications:
E57-81 is a one-component, solventless Class H heat-resistant polyester insulating resin formulated with modified unsaturated polyester resin, reactive diluents, stabilizers, and performance additives. It is engineered for electrical insulation impregnation applications that require reliable thermal resistance, dielectric performance, and mechanical durability.
The resin provides strong adhesion, good penetration, excellent electrical insulation, and high mechanical strength. It also offers moisture and mildew resistance, fast baking cure, and strong compatibility with commonly used insulating materials. With reliable resistance to high- and low-temperature thermal shock, E57-81 is easy to process in both vacuum-pressure and atmospheric impregnation systems.
E57-81 is widely used for insulating B, F, H, and C class dry-type power transformers, reactors, EV motors, large generators, hoisting motors, variable-frequency motors, and refrigerant-resistant motors.
- Description
- Technical Data
- FAQ
Description
Product Features:
· Modified heat-resistant unsaturated 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) Reactive diluent: X-68. | |
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 E57-81?
The standard MOQ for E57-81 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?
E57-81 is supplied in the following standard packaging:
- 18 kg per pail
Please contact us for bulk-order pricing, OEM labeling, export packaging, 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 and related delivery charges.
What is E57-81 used for?
E57-81 is a one-component, solventless Class H heat-resistant polyester insulating resin designed for electrical insulation applications. It is widely used for vacuum impregnation and atmospheric-pressure impregnation of B, F, H, and C class dry-type power transformers, reactors, EV motors, large generators, hoisting motors, variable-frequency motors, refrigerant-resistant motors, and compatible electrical windings.
Is E57-81 suitable for vacuum impregnation?
Yes. E57-81 is suitable for compatible vacuum impregnation and atmospheric-pressure impregnation processes. It can be used for transformer windings, reactor coils, motor windings, generator components, and other electrical components that require heat-cured insulation treatment.
Does E57-81 require baking?
Yes. E57-81 is a fast 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 E57-81 compatible with different insulation materials?
E57-81 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 E57-81?
E57-81 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 E57-81 be stored?
Store E57-81 in its original, unopened packaging in a cool, dry, and well-ventilated area. Keep the pail tightly sealed when not in use and follow the storage and handling instructions provided in the Technical Data Sheet (TDS) or Safety Data Sheet (SDS).
Can you provide technical and compliance documents?
Technical and quality documents may include the Technical Data Sheet (TDS), Safety Data Sheet (SDS), Certificate of Analysis (COA), and applicable compliance documentation. Please contact us to confirm the documents required for your project.
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.