E57-160F Class F Solvent-Free Insulating Varnish
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Short Product Description：
E57-160F is a Class F solvent-free insulating varnish based on modified unsaturated polyester resin with styrene as a reactive diluent. Designed for impregnation of EI-35 to EI-105 transformers, it combines low viscosity, strong adhesion, and heat-curing performance. The system uses the specified G160F or G160F-2 curing agent and X-58 thinner for application adjustment.
- Description
- Technical Data
- FAQ
Description
Product Overview:
E57-160F is an electrical insulating varnish developed for transformer impregnation. Its modified unsaturated polyester formulation uses a reactive diluent and curing system to form a bonded insulating structure after heat curing.
Strong adhesion between transformer components helps reduce electromagnetic vibration and associated noise. The varnish has a reported viscosity of 18–22 seconds using a Tu-4 cup at 25°C, supporting its use in transformer impregnation processes.
This Class F insulating varnish is rated at 155°C in the TDS. Reported cured properties include a volume resistivity of 4 × 10¹³ Ω·m and dielectric strength of 20.5 kV/mm under normal conditions.
E57-160F is described by the manufacturer as solvent-free, with styrene serving as a reactive diluent. This designation does not mean zero emissions or nonflammability; appropriate ventilation and process controls remain necessary.
Key Features and Benefits：
· Class F Heat Resistance: Rated Class F, 155°C, in the TDS, supporting selection for corresponding electrical insulation requirements.
· Strong Transformer Component Bonding: Helps secure transformer components and reduce electromagnetic vibration and associated noise.
· Low Application Viscosity: A reported viscosity of 18–22 seconds at 25°C supports transformer impregnation using a validated production process.
· Heat-Curing Performance: Reference curing schedules of 110°C for 3 hours or 120°C for 2 hours provide starting points for process development.
· Electrical Insulation: The TDS reports dielectric strength of 20.5 kV/mm and volume resistivity of 4 × 10¹³ Ω·m under normal conditions.
· Mechanical Bonding Performance: Reported shear bonding force is ≥300 N at 23°C using Ø2.0 mm PEW wire under the stated test conditions.
· Reactive Diluent Formulation: Uses styrene as a reactive diluent within the unsaturated polyester system.
· Specified Processing Materials: X-58 thinner and G160F or G160F-2 curing agent are identified for preparation and application adjustment.
Typical Applications：
E57-160F insulating varnish is primarily intended for:
· EI Transformers: Impregnation of transformer sizes EI-35 to EI-105, as specified in the TDS.
· Transformer Winding Assemblies: Electrical insulation and bonding of components within impregnated assemblies.
· Automated Transformer Impregnation Processes: Evaluation for production equipment combining impregnation and drying; the TDS references an EI-66 transformer example using an automatic impregnation and drying system.
Determine suitability and processing conditions using the actual transformer geometry, winding materials, equipment, and required electrical performance.
Physical Properties：
| Item | Specification | ||||
| Varnish Properties | Appearance | Visual | Yellow, transparent liquid | ||
| Viscosity (Tu-4 Cup) | 25℃, s | 18-22 | |||
| Specific Gravity | 25℃ | 0.99±0.02 | |||
| Gel Time | 100℃, min | ≥5.0 | |||
| Pot Life | 40℃, days | ≥5 days | |||
| Drying Time | Galvanized iron sheet | 100-120℃, min | ≤20 | ||
| Cured Film Properties | Volume Resistivity | Normal state, Ω·m | 4×1013 | ||
| Dielectric Breakdown Strength | Normal state | KV/mm | 20.5 | ||
| Shear Adhesion (using Ф2.0mm PEW) | 23℃ | N | ≥300 | ||
| Curing Conditions | – | 110℃/3h or 120℃/2h | |||
Example of varnish impregnation conditions (Model EI-66, using an automatic impregnation and drying system)
| Treatment Item | Unit | treatment conditions |
| Preheating | ℃/min | 110/10～20 |
| Air cooling | min | 5～10 |
| Impregnation | min | 2～5 |
| Drip removal | min | 5～20 |
| Curing | ℃/min | 120/60 |
Technical Notes:
· Viscosity is expressed as cup flow time in seconds.
· Specific gravity is dimensionless, and volume resistivity is reported in Ω·m.
Application Guidance：
· Material Preparation
Use the specified X-58 thinner and either G160F or G160F-2 curing agent according to the supplier’s instructions.
The TDS gives the following reference ratio:
· Varnish : Thinner : Curing Agent = 100 : 0–200 : 2
The document does not state whether this ratio is by weight or volume. Confirm the ratio basis, thinner addition, curing-agent selection, and mixing procedure with the supplier before preparing a production batch.
· Transformer Impregnation
Determine the dilution ratio, impregnation time, and curing cycle through trials based on transformer size, winding structure, and production equipment.
For EI-35 to EI-105 transformers, verify impregnation quality, bonding, and electrical performance on the actual assembly before approving the process.
· Reference Curing Conditions
| Curing Temperature | Reference Curing Time |
|---|---|
| 110°C | 3 h |
| 120°C | 2 h |
These schedules are starting points for process validation. Actual curing depends on the prepared formulation, retained varnish quantity, transformer geometry, component heating, and oven loading.
Do not use the thin-sheet drying time or gel time as a substitute for complete transformer curing.
· Working Bath Management
Prevent water contamination. The TDS states that the product is sensitive to temperature and humidity; follow first-in, first-out stock rotation and use prepared material within its validated working life.
Monitor viscosity, specific gravity, and bath temperature. If properties change significantly, consult the supplier’s replenishment or adjustment procedure before adding fresh material or thinner.
The TDS warns that material in prolonged use can generate heat through reaction. Manage active or mixed varnish using a supplier-approved system that allows safe heat dissipation. Do not confine reacting material in a sealed container.
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 E57-160F Insulating Varnish
1. What is E57-160F insulating varnish used for?
E57-160F is a heat-curing modified unsaturated polyester insulating varnish developed for transformer impregnation. The TDS specifically identifies EI-35 to EI-105 transformers as intended applications.
After curing, it provides electrical insulation and bonds transformer components, helping reduce electromagnetic vibration and associated noise. Validate compatibility with the actual winding materials and transformer construction before production use.
2. What is the thermal class of E57-160F?
E57-160F is rated Class F, 155°C, in the TDS. It supports selection for transformer insulation systems requiring this thermal class.
The rating is separate from the reference curing temperatures of 110°C and 120°C. A finished transformer’s allowable operating temperature depends on the complete insulation system, component design, and service conditions.
3. Is E57-160F solvent-free?
The manufacturer describes E57-160F as solvent-free, with styrene serving as a reactive diluent in the unsaturated polyester formulation.
This designation does not mean zero emissions or nonflammability. The product is identified as flammable in the supplied handling guidance. Follow the applicable MSDS and provide suitable ventilation during preparation, impregnation, and curing.
4. Does E57-160F require a curing agent and thinner?
The TDS specifies G160F or G160F-2 curing agent and X-58 thinner for material preparation. Its reference ratio is E57-160F varnish : X-58 thinner : curing agent = 100 : 0–200 : 2.
The document does not identify whether this ratio is by weight or volume. Confirm the ratio basis, required thinner addition, curing-agent selection, and mixing sequence with the supplier before preparing a batch. Validate the formulation on the actual transformer.
5. What curing temperature and time are recommended for E57-160F?
The TDS provides two reference curing schedules: three hours at 110°C or two hours at 120°C.
Validate the selected schedule according to the prepared formulation, retained varnish quantity, transformer geometry, component heating, and oven loading. Confirm complete curing within the winding assembly before electrical testing or service.
6. Can an impregnated transformer cure in 20 minutes?
The reported drying time of no more than 20 minutes at 100–120°C was measured on galvanized iron sheet. It does not establish the full curing time of an impregnated transformer.
Gel time, thin-sheet drying time, and assembly curing time describe different process stages. Use the transformer curing guidance and application trials to establish the production cycle.
7. Can E57-160F be used on an automatic transformer impregnation line?
Yes. The TDS includes an EI-66 transformer example using an automatic impregnation and drying system. The example specifies preheating at 110°C for 10–20 minutes, air cooling for 5–10 minutes, impregnation for 2–5 minutes, drip removal for 5–20 minutes, and curing at 120°C for 60 minutes.
This equipment-specific example differs from the general reference cure of two hours at 120°C. Confirm the conditions needed to reproduce it before applying the shorter cycle to another production line or transformer design.
8. How does E57-160F help bond transformer components?
E57-160F forms a bonded insulating structure after heat curing, helping secure transformer components and limit movement associated with electromagnetic vibration and noise.
The TDS reports a shear bonding force of at least 300 N at 23°C using Ø2.0 mm PEW wire under the stated test conditions. This is a force measurement, not a bond stress in MPa. Actual assembly performance depends on impregnation quality, material compatibility, and curing.
9. What electrical insulation performance does E57-160F provide?
The E57-160F TDS reports dielectric strength of 20.5 kV/mm and volume resistivity of 4 × 10¹³ Ω·m under normal conditions.
These values describe the cured insulating material. They do not directly establish the allowable operating voltage of a finished transformer, which also depends on insulation design, clearances, winding construction, and processing quality.
10. What is the working life of prepared E57-160F?
The TDS lists a pot-life value of at least five days at 40°C, but it does not specify the mixture composition or test endpoint associated with that value.
Confirm its applicability to the selected varnish, thinner, and curing-agent mixture before setting a production working-life limit. The pot-life value is separate from the six-month storage shelf life of the sealed product.
11. How should an E57-160F impregnation bath be managed?
Prevent water contamination and monitor viscosity, specific gravity, and bath temperature. Follow the supplier’s adjustment procedure if properties change significantly rather than adding thinner or fresh material without confirmation.
The TDS warns that material in prolonged use can generate heat through reaction. Use a supplier-approved bath-management procedure that allows safe heat dissipation, and do not seal actively reacting material in a container.
12. What safety and compliance documents are available for E57-160F?
Our Insulating Varnish downloads section lists an MSDS, RoHS documentation, and a VOC content test report. Specify E57-160F when requesting documents so the applicable report or declaration and its product coverage can be confirmed.
The Thinners section separately lists RoHS documentation and a halogen content test report.
13. How is E57-160F packaged and stored?
E57-160F is supplied in 18 kg metal pails. Its stated shelf life is six months when stored sealed at 5–25°C.
Store the original product in a cool, dark, dry location away from fire and heat sources. Follow the applicable MSDS and manage prepared or reacting mixtures separately according to the supplier’s working-life and heat-dissipation instructions.
14. What information should I provide when requesting an E57-160F quotation?
Include the transformer model and dimensions, winding materials, impregnation equipment, available curing conditions, and required electrical and bonding performance. If using an automatic line, provide its processing sequence and target cycle time.
For pricing and delivery, include the required quantity, delivery destination, target delivery date, and any requirements for X-58 thinner, curing agent, trial material, or compliance documents.