What Is Addition-Cure Liquid Fluorosilicone Rubber?
Addition-cure liquid fluorosilicone rubber, commonly known as F-LSR, is a two-component liquid elastomer based on vinyl fluorosilicone oil, combined with a hydrogen-containing crosslinker and a platinum catalyst.Compared with ordinary liquid silicone rubber, it introduces trifluoropropyl groups into the polymer chain, significantly improving resistance to fuels, oils, solvents and non-polar chemical media. Compared with solid fluorosilicone rubber compounds, it offers better flow and injection-molding capability, making it suitable for complex, precision and high-volume sealing and functional parts.
The material typically appears as a homogeneous fluid or paste without visible impurities. It can be mixed at a 1:1 ratio and processed by liquid injection molding, compression molding or coating.The platinum addition-cure process generates no small-molecule by-products, supporting high dimensional stability, good surface quality and reliable sealing performance.
Key Technical Indicators
Hardness Range
Common Shore A hardness grades include 30, 40, 50 and 60, with some products extending to 70 or higher.Lower hardness grades provide better flexibility for diaphragms, hoses and dynamic seals; higher hardness grades offer higher modulus for O-rings, gaskets and static seals.
Viscosity and Processability
Typical viscosity is around 600-1000 Pa·s, varying with hardness and formulation.This range supports liquid injection molding, precision compression molding and coating, allowing complex cavities to be filled under relatively low injection pressure while reducing flash and improving part consistency.
Tensile and Tear Strength
According to the group standard T/FSI 071-2021, tensile strength is generally not less than 8.0 MPa, and tear strength increases with hardness, commonly ranging from about 10.0 to 15.0 kN/m.Higher tensile and tear performance helps seals maintain reliability under pressure fluctuation, vibration and assembly compression.
Compression Set
Compression set is a key indicator of long-term sealing resilience. Addition-cure liquid fluorosilicone rubber typically shows a compression set of no more than 30% after 177°C for 22 h, with some high-performance grades achieving lower values.Low compression set means the seal can maintain rebound force and contact pressure after long-term high-temperature compression.
Oil and Solvent Resistance
The material offers excellent resistance to fuels, engine oils, lubricants and many non-polar solvents. In IRM903 standard oil at 23°C for 24 h, volume swell is typically no more than 3%; in reference liquids B and C, volume change is generally no more than 30%.This makes it especially suitable for fuel systems, lubrication systems and chemical media exposure.
Service Temperature Range
Addition-cure liquid fluorosilicone rubber usually maintains elasticity over a wide temperature range, with a common immersed-service range of about -63°C to +175°C and higher tolerance under dry heat.Compared with fluorocarbon rubber, it provides better low-temperature elasticity; compared with ordinary silicone rubber, it offers stronger stability in fuel and oil environments.
Curing System
The material cures via platinum-catalyzed addition reaction. Part A usually contains the platinum catalyst, and Part B contains the hydrogen-containing crosslinker.The curing process releases no by-products and shows low shrinkage, making it suitable for precision seals, electronic connectors and thin diaphragms. Amines, sulfur compounds, tin compounds and some peroxides may inhibit platinum curing and should be avoided.
Main Performance Features
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Fuel, oil and solvent resistance: trifluoropropyl groups improve resistance to non-polar media.
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Injection-moldable: suitable for LIM, compression molding and precision parts.
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Low compression set: maintains resilience and sealing force after long-term compression.
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Wide-temperature elasticity: flexible at low temperature and stable at high temperature.
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By-product-free curing: platinum addition cure ensures dimensional stability and surface quality.
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Stable electrical insulation: suitable for connectors, sensors and electrical protection.
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Selectable hardness: from 30A to 70A and above for different sealing needs.
Typical Application Scenarios
Automotive Fuel System Seals
Suitable for fuel pump diaphragms, injector O-rings, fuel line seals, fuel cap gaskets and quick-connector seals, maintaining reliability under fuel, oil and temperature cycling.
New Energy Vehicle Powertrain Systems
Applicable to drive motor oil-cooling seals, battery pack liquid-cooling tube seals, high-voltage connector seals and harness insulation sleeves, meeting requirements for cooling-media resistance, oil resistance and long-term sealing reliability.
Aerospace Fuel and Hydraulic Seals
Can be used in aircraft fuel system seals, avionics encapsulation, vent valves and diaphragms, meeting requirements for aviation fuel resistance, lubricant resistance and wide-temperature performance.
Turbocharger and Engine Peripherals
Suitable for turbocharger hose liners, high-temperature oil-resistant engine seals, sensor seals and high-temperature hoses, balancing heat resistance, oil resistance and dynamic fatigue performance.
Electrical Connectors and Potting Protection
Applicable to electrical connectors, sensor encapsulation, precision electronic component protection and solvent-resistant coatings, improving stability in humid, oily and chemical environments.
Industrial Seals and Chemical Equipment Parts
Suitable for solvent-resistant gaskets, valve diaphragms, pump and valve seals and small precision seals in chemical environments, especially where fuel, lubricant and non-polar solvent resistance are required.
Selection and Usage Recommendations
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Select hardness by sealing type: choose 30A-50A for dynamic seals and diaphragms; choose 60A-70A for static O-rings and gaskets.
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Confirm media resistance: verify volume swell and hardness change for fuels, engine oils, IRM903 oil, reference liquids B/C and other media.
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Check compression set: for long-term high-temperature sealing, confirm compression set at 177°C for 22 h or equivalent conditions.
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Match injection molding process: confirm viscosity, mix ratio, pot life and cure temperature; avoid air entrapment and platinum inhibitors.
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Distinguish liquid from solid FVMQ: liquid fluorosilicone rubber suits precision injection molding and mass production; solid fluorosilicone compounds suit compression molding, extrusion and thick-walled parts.
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Key points for overseas customers: highlight fuel/oil/solvent resistance, wide-temperature sealing, low compression set, injection-moldability and platinum addition curing to support sample delivery, mold trials and bulk adoption.
IOTA FLSR3400 addition-type liquid fluorosilicone rubber
