The sealing components of power transformers are exposed to harsh conditions such as high temperatures, immersion in transformer oil, and alternating high and low temperatures for a long time. Ordinary organic silicon rubbers have poor performance in resisting transformer oil and tend to swell significantly after being soaked in oil, resulting in deterioration of dielectric properties. Conventional fluorine rubbers have insufficient low-temperature performance and tend to harden and become brittle at low temperatures, increasing the risk of sealing failure. Moreover, most power sealing components are produced using molding or injection molding processes, which have strict requirements for the processing fluidity, compression permanent deformation, and dielectric loss indicators of the rubber materials. IOTA F5672 is a specialized fluorosilicone compound designed for power transformer sealing components, taking into account the ease of processing, mechanical properties, and oil resistance. It has a lower dielectric loss in transformer oil and provides a material selection solution for oil-resistant sealing products in the power industry.


IOTA F5672 is a fluorosilicone compound product. After adding an appropriate curing agent, it can be thermally cured and molded. The type and amount of the curing agent can be flexibly adjusted according to the downstream molding process. The most notable feature of this product is its balance of oil resistance, low-temperature performance, dielectric properties, and processing performance. Ordinary fluorosilicone rubbers, although resistant to fuel oil, tend to expand significantly when soaked in transformer oil, resulting in increased dielectric loss and failing to meet the insulation requirements for power equipment. In contrast, IOTA F5672 has outstanding performance in resisting 25# transformer oil, while retaining the excellent high and low-temperature resistance of fluorosilicone materials, suitable for the long-term stable operation of transformers.


The product appearance is a light yellow rubber material with a density of 1.43g/cm³ and a hardness of 70 Shore A, which is a common hardness grade for transformer sealing gaskets and special-shaped sealing components. The basic mechanical properties are excellent: tensile strength 9.2MPa, elongation at break 230%, tear strength 20KN/m, and elastic recovery 33%. Under the test condition of 150℃×24h (Type B), the compression permanent deformation is only 5% after 72 hours of aging at 200℃, showing excellent rebound performance in a high-temperature pressurized working environment, with small sealing stress attenuation, avoiding permanent deformation of the sealing gasket that may cause oil leakage faults.


Heat aging test: After 72 hours of aging at 200℃, the hardness only increases by 2 Shore A, the tensile strength change rate is -15%, and the elongation at break change rate is -18%. The mechanical properties of the material show a small attenuation after high-temperature aging, with strong material stability. After 100℃ immersion in 25# transformer oil for 168 hours, the hardness change is only 3 Shore A, and the volume change rate is as low as 2.2%. The anti-oil swelling ability is outstanding; the low-temperature brittleness temperature can reach -60℃, and it will not easily crack in outdoor transformer equipment in cold regions. The Fuel C fuel has a volume change rate of +20% after 72 hours of immersion at 25℃, while also balancing the ability to resist fuel oil and lubricating oil media.


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Note: All performance data in the table are typical reference values and are not regarded as the factory acceptance standards. The actual physical properties are affected by the vulcanization process and processing conditions.


## Recommended Vulcanization Process Scheme


Vulcanization agent selection: 2,5 - Di-methyl - 2,5 - Bis-(tert-butyl peroxy) hexane (40% content)
Recommended dosage: 0.6 - 1.2 parts
One-stage vulcanization: 170℃ × 15min
Two-stage vulcanization: 200℃ × 4h


This product is suitable for both compression molding and injection molding processes, and is highly suitable for mass production of transformer sealing gaskets and special-shaped sealing rings. Manufacturers can adjust the vulcanization temperature, holding time, and dosage of the vulcanization agent according to the thickness of the product, mold structure, and molding method. The second-stage vulcanization process is crucial as it can remove small molecule by-products of the vulcanization reaction, further reducing dielectric loss, improving oil resistance and compression permanent deformation indicators. Skipping the second-stage vulcanization will directly affect the long-term reliability of the electrical sealing components.


## Main Application Fields


1. Power Transformer Industry: Transformer oil-resistant sealing gaskets, flange sealing parts, cable sleeve sealing parts, elastic sealing products that come into long-term contact with 25# transformer oil;
2. Electrical Equipment: Molded/Injection sealing accessories that require oil resistance, high-temperature resistance, and low dielectric loss in high and low voltage electrical equipment;
3. Industrial Special Seals: Molded/Injection elastic components that need to resist mineral oil, operate in a wide temperature range, and have high requirements for compression permanent deformation.


## Processing Practical Considerations


1. Mixing Operation: Mix evenly in the open mill and then add the 2,5 - Di-methyl - 2,5 - Bis-(tert-butyl peroxy) hexane vulcanization agent. Thoroughly blend to ensure the vulcanization agent is evenly dispersed, preventing local concentration of the vulcanization agent that may cause internal bubbles and local scorching of the product;
2. Mold Selection: The main focus is on compression molding and injection molding. It is not recommended to use production lines that mainly rely on extrusion. Small-scale tests should be conducted before extrusion molding;
3. Dielectric Performance Control: To maintain a low dielectric loss of transformer oil, the complete two-stage vulcanization must be strictly followed. Avoid moisture absorption and the introduction of conductive impurities during raw material storage;
4. Storage Specifications: The storage environment temperature should be below 40℃ for unopened original packaging. The shelf life is 12 months from the production date; Store in a cool and ventilated place, away from heat sources, to prevent the rubber material from prematurely cross-linking;
5. Sample Testing: Before formal mass production, it is recommended to make samples to test the resistance to transformer oil, compression permanent deformation, and related dielectric indicators. Confirm that the material performance meets the working conditions standards before mass production.


## Common Questions in the Industry


Q: Why is IOTA F5672 suitable for transformer sealing parts?
A: The core advantage is that it has an extremely low swelling rate in 25# transformer oil, a compression permanent deformation of only 5%, and low low-temperature brittleness - -60℃, and does not become brittle at low temperatures. Moreover, the formula controls the dielectric loss of transformer oil, meeting the insulation sealing requirements of power equipment, and the processing of compression molding and injection molding is simple.


Q: How is the dosage range of 0.6 - 1.2 parts for the 2,5 - Di-methyl - 2,5 - Bis-(tert-butyl peroxy) hexane vulcanization agent determined?
A: The dosage can be selected at a lower level for thin-walled products and injection molding; for thick-walled compression molding parts, the dosage can be appropriately increased. The final dosage needs to be determined based on small-scale tests, considering the degree of cross-linking, mechanical properties, and oil resistance indicators.


Q: What does a 2.2% volume change in transformer oil represent?
A: Under 100℃ and 168h of long-term immersion in 25# transformer oil, the volume only expands by 2.2%. Compared to the swelling degree of ordinary fluorosilicone rubber, it is significantly reduced, effectively preventing the expansion and deformation of the sealing part and oil leakage after long-term immersion in oil. 


With the promotion of the construction of new power systems in China, the domestic production of transformer equipment is continuously accelerating, and the requirements for oil resistance, low-temperature resistance, low compression permanent deformation, and dielectric stability of power sealing materials are constantly upgrading. Traditional sealing materials either have insufficient oil resistance or poor low-temperature performance, making it difficult to meet multiple requirements simultaneously. The IOTA F5672 transformer-specific fluorosilicone compound focuses on the sealing niche of power transformers, with core selling points including low transformer oil swelling, low compression permanent deformation, and -60℃ low-temperature performance. It is suitable for compression molding and injection molding processes, reducing the difficulty for power rubber product manufacturers in material selection and process debugging. When selecting materials for the downstream, it is necessary to conduct sample evaluations based on the actual working temperature of the equipment, the type of transformer oil, and the sealing structure, to determine the final processing plan and ensure the long-term safe operation of power equipment.