What Is Addition-Cure Liquid Fluorosilicone Rubber?
Addition-cure liquid fluorosilicone rubber is a liquid-processable fluorosilicone material, typically consisting of vinyl-functional fluorosilicone polymer as the base and hydrogen-containing fluorosilicone oil as the crosslinker, cured through platinum-catalyzed hydrosilylation.Unlike condensation-cure systems, it generates almost no small-molecule by-products during curing, resulting in low shrinkage, high dimensional stability and better suitability for precision seals, potting compounds and complex molded components.
Fluorosilicone rubber has a siloxane main chain with fluoroalkyl side groups such as trifluoropropyl, giving it both the wide-temperature elasticity of silicone rubber and the oil/solvent resistance of fluororubber.Addition-cure liquid fluorosilicone rubber further improves processability, allowing injection molding, compression molding and casting potting, making it suitable for applications requiring high sealing reliability, media resistance and consistent production quality.
Compared with ordinary liquid silicone rubber, addition-cure liquid fluorosilicone rubber offers stronger resistance to fuels, lubricating oils, hydraulic oils and non-polar solvents. Compared with peroxide-cured fluorosilicone rubber, it generally provides faster molding efficiency, fewer by-product risks and more stable compression set performance.
Key Technical Indicators
Vinyl Fluorosilicone Oil and Hydrogen-Containing Fluorosilicone Oil Ratio
The crosslinked network is formed by hydrosilylation between vinyl fluorosilicone oil and hydrogen-containing fluorosilicone oil. Vinyl content affects crosslink density, hardness, tensile strength and resilience, while the amount of hydrogen-containing fluorosilicone oil influences curing degree and compression set. The ratio should be adjusted according to hardness, media resistance, molding process and final part performance.
Platinum Catalytic System
The platinum catalyst determines curing speed and process controllability. Inhibitors can be used to adjust pot life and curing window, enabling the material to suit injection molding, compression molding or potting processes.Nitrogen-, sulfur-, phosphorus-containing substances or certain heavy metals may inhibit the platinum catalyst and cause incomplete curing, so substrate cleanliness and environmental control are critical.
Oil and Solvent Resistance
Addition-cure liquid fluorosilicone rubber shows good resistance to aviation fuel, gasoline, lubricating oil, hydraulic oil and non-polar solvents, with significantly lower volume swelling than ordinary silicone rubber.This makes it especially suitable for seals, gaskets and potting protection in fuel systems, hydraulic systems and lubricant-exposed environments.
Wide-Temperature Performance
Fluorosilicone rubber typically maintains elasticity from -55°C to above 200°C, with some grades tolerating higher short-term temperatures.The addition-cure system forms a more uniform crosslinked network, helping maintain sealing force and resilience across wide temperature ranges, making it suitable for thermal cycling, engine compartments, aerospace equipment and harsh outdoor environments.
Low Compression Set
Compression set is a key indicator of long-term sealing reliability. Addition-cure liquid fluorosilicone rubber can achieve low compression set by optimizing vinyl/hydrogen ratio, filler treatment and post-curing, making it suitable for O-rings, gaskets, valve stem seals and long-term compressed sealing structures.
Mechanical Properties and Resilience
This material generally offers high tensile strength, good tear strength and high rebound resilience, maintaining sealing integrity under vibration, pulse pressure and repeated compression.For dynamic seals, fuel pump seals, hydraulic joints and aerospace bellows, resilience and fatigue resistance should be carefully verified.
Potting and Molding Compatibility
Addition-cure liquid fluorosilicone rubber can be adjusted in viscosity, thixotropy and curing speed to suit potting, injection molding and compression molding. Low-viscosity grades are suitable for deep potting and complex cavity filling; higher-viscosity grades are better for molded seals and thick-section parts.
Main Performance Features
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Fuel and oil resistant: good resistance to aviation fuel, gasoline, engine oil, hydraulic oil and non-polar solvents.
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Wide-temperature elasticity: maintains sealing performance from -55°C to above 200°C.
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Low compression set: suitable for long-term compressed seals and precision O-rings.
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No small-molecule by-products during cure: high dimensional stability for precision molding and potting.
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Good resilience and fatigue resistance: suitable for dynamic seals, vibration environments and pulse pressure conditions.
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Injection-moldable and potting-compatible: supports automated production, complex structures and deep encapsulation.
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Customizable formulation: viscosity, hardness and curing speed can be adjusted for different application needs.
Typical Application Scenarios
Automotive Fuel System Sealing
Used for fuel pump seals, injector O-rings, fuel line connectors, fuel valve seals and engine-compartment oil-resistant seals, meeting long-term sealing requirements under fuel, lubricant and high-temperature conditions.
Aerospace Fuel Tank and Hydraulic Sealing
Applicable to aircraft integral fuel tank sealing, fuel system gaskets, hydraulic bellows, sealing rings and oil-resistant potting for aerospace equipment, combining fuel resistance, low-temperature performance and wide-temperature reliability.
New Energy Vehicle E-Drive Sealing
Suitable for motor, controller, cooling line and high-voltage connector sealing where oil, coolant and media resistance are required, especially for structures needing low compression set and long-term reliability.
Electronic and Electrical Potting
Used for potting sensors, connectors, control modules and outdoor electronic equipment, providing sealing, vibration damping, moisture protection and certain chemical media resistance.
Industrial Hydraulic and Lubrication Sealing
Applicable to hydraulic valves, oil pumps, sealing rings, gaskets and industrial equipment seals, maintaining stability in lubricating oil, hydraulic oil and non-polar solvent environments.
Precision Molded Seals
Can be injection-molded or compression-molded into complex O-rings, special-shaped gaskets, valve seat seals and small oil-resistant elastic parts, suitable for batch production.
Selection and Usage Recommendations
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Define media type: fuels, lubricants, hydraulic oils, solvents and coolants affect the material differently; selection should match actual exposure conditions.
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Confirm temperature range: for long-term high-temperature or thermal cycling service, evaluate compression set, hardness and resilience retention.
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Match molding process: injection molding, compression molding and potting have different requirements for viscosity, pot life and curing speed.
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Avoid platinum catalyst poisoning: prevent contact with nitrogen-, sulfur-, phosphorus-, tin- or heavy-metal-containing substances; keep substrates clean and dry.
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Apply post-curing when needed: for low compression set seals, post-curing is recommended to improve long-term stability.
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Key points for overseas customers: emphasize fuel/oil resistance, low compression set, platinum-cure by-product-free process, automotive and aerospace sealing potential, potting and molding compatibility, and customization of viscosity, hardness and curing speed to support media immersion tests, sealing life evaluation and bulk adoption.
IOTA FLSR3400 addition-type liquid fluorosilicone rubber
