What Is Addition-Cure Liquid Fluorosilicone Rubber?
Addition-cure liquid fluorosilicone rubber is a liquid elastomer based on fluorosiloxane polymers and cured through a platinum-catalyzed addition reaction. Unlike peroxide-cured fluorosilicone rubber, it forms a crosslinked network by reacting vinyl groups with hydrosiloxane groups in the presence of a platinum catalyst. The curing process generally produces no small-molecule by-products, resulting in better dimensional stability and easier control of surface appearance.
This material is usually supplied as a two-component system, mixed in a specified ratio before use, and can cure at room temperature or under heating. Depending on the formulation, it can be developed into low-viscosity potting compounds, medium-to-high viscosity sealant coatings, injectable liquid fluorosilicone rubber or moldable fluorosilicone elastomers. Its key advantage lies in combining resistance to fuels, lubricating oils, hydraulic oils and certain hydrocarbon solvents with excellent high/low-temperature performance and low compression set.
Addition-cure liquid fluorosilicone rubber maintains good thermal and oil resistance even without halogenated flame-retardant systems. Some grades can be modified with flame-retardant, thermally conductive or thixotropic fillers to meet requirements in automotive electronics, aerospace, sensors, connectors, seals and industrial potting applications.
Key Technical Indicators
Viscosity and Flow Behavior
Addition-cure liquid fluorosilicone rubber is available in a wide viscosity range. Low-viscosity grades are suitable for potting, impregnation and filling complex structures, while medium-to-high viscosity grades are better for sealant coatings, dispensing and molding. Potting applications typically focus on flowability, air release and self-leveling, whereas dispensing and molding applications require better thixotropy and anti-sag performance.
Platinum-Cure System
The addition-cure system relies on a platinum catalyst to achieve crosslinking. Curing speed can be adjusted through temperature, catalyst dosage and inhibitors. Compared with peroxide vulcanization, addition curing usually produces less odor, fewer by-products and more controllable shrinkage, making it suitable for transparent or high-appearance applications. However, substances containing nitrogen, sulfur, phosphorus, tin, mercury or certain heavy metals may inhibit the platinum catalyst, so material compatibility should be confirmed before use.
Oil and Solvent Resistance
The fluorosilicone polymer chain contains fluorinated groups such as trifluoropropyl, providing good resistance to fuels, lubricating oils, hydraulic oils and certain hydrocarbon solvents. Compared with ordinary silicone rubber, addition-cure liquid fluorosilicone rubber is less prone to severe swelling or performance loss when exposed to oil-based media.
High/Low-Temperature Performance
Addition-cure liquid fluorosilicone rubber can typically maintain elasticity from about -55°C to +200°C, with some grades able to withstand higher temperatures for short periods. It remains flexible at low temperatures and shows good thermal aging stability at elevated temperatures, making it suitable for wide-temperature sealing and potting protection.
Compression Set
Compression set is a critical indicator for seals and gaskets. Due to its relatively regular crosslinked network, addition-cure liquid fluorosilicone rubber can achieve low compression set, supporting long-term sealing reliability.
Hardness and Mechanical Properties
Cured hardness can be adjusted according to application needs, commonly ranging from about Shore A 10-80 or higher. Tensile strength, tear strength and elongation vary with hardness, filler systems and curing conditions. Seals, gaskets and connector potting usually require a balance between hardness, resilience and mechanical strength.
Flame Retardancy and Electrical Properties
Some addition-cure liquid fluorosilicone rubber grades can achieve UL94 V-0 or similar flame-retardant levels through flame-retardant fillers while maintaining good electrical insulation. For electronic potting, dielectric strength, volume resistivity, arc resistance and low moisture absorption should also be considered.
Storage and Pot Life
Two-component addition-cure liquid fluorosilicone rubber has a limited pot life after mixing and must be used for potting, dispensing or molding within the applicable time. Unmixed components should be stored sealed, protected from light and moisture, and kept away from catalyst inhibitors and heavy-metal impurities.
Main Performance Features
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Oil and fuel resistant: good resistance to fuels, lubricating oils, hydraulic oils and certain hydrocarbon solvents.
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Wide temperature resistance: maintains elasticity across high and low temperatures.
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Platinum addition cure: low by-products, good dimensional stability, suitable for precision potting and high-appearance parts.
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Low compression set: supports long-term sealing reliability under repeated compression.
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Suitable for potting and molding: applicable to electronic potting, connector protection, gasket molding and sealant coatings.
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Good electrical insulation: suitable for sensors, wire harnesses, connectors and automotive electronics protection.
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Flame-retardant and thermally conductive options: viscosity, hardness, flame retardancy and thermal conductivity can be customized.
Typical Application Scenarios
Automotive Electronics Potting and Protection
Used for potting protection of engine-area sensors, control units, wire harness connectors, ignition modules and onboard electronic modules, combining oil resistance, vibration resistance, wide-temperature performance and electrical insulation.
Fuel System Seals and Coatings
Suitable for fuel pumps, fuel sensors, fuel-line seals and elastic coatings in contact with fuel media, reducing the swelling risk of ordinary silicone rubber in fuel environments.
Aerospace Sealing and Potting
Applied in aviation hydraulic systems, fuel systems, sensor potting and oil-resistant seals, meeting wide-temperature, media-resistant and high-reliability requirements.
Connector and Sensor Encapsulation
Used for connector potting, sensor encapsulation and signal module protection in oil-exposed or high/low-temperature environments, improving sealing, insulation and environmental resistance.
Industrial Oil-Resistant Seals
Suitable for hydraulic equipment, oil pumps, valves, gaskets and sealing structures in contact with lubricating oils or solvents, extending service life.
Flame-Retardant Electronic Potting Compounds
With flame-retardant formulation adjustment, it can be used for electronic modules, power components, battery management systems and industrial control units requiring higher fire safety performance.
Selection and Usage Recommendations
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Choose viscosity by potting or molding needs: low viscosity is preferred for deep-cavity potting and degassing; thixotropic medium-to-high viscosity is better for dispensing and sealant coatings.
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Confirm media resistance: different fuels, lubricants, hydraulic oils and solvents affect materials differently, so swelling and aging tests should be conducted under actual conditions.
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Check platinum catalyst compatibility: avoid contact with nitrogen-, sulfur-, phosphorus-, tin- or mercury-containing substances that may inhibit curing; small-sample curing tests are recommended.
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Evaluate compression set: for seals, gaskets and repeatedly compressed structures, test compression set and performance retention after heat aging.
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Confirm flame-retardant and electrical requirements: electronic potting applications should specify flame-retardant rating, dielectric strength, volume resistivity and arc resistance.
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Key points for overseas customers: emphasize oil/fuel resistance, wide-temperature performance, platinum addition cure, low compression set, suitability for automotive electronics potting and sealing, and customization by viscosity, hardness, flame retardancy and thermal conductivity to support sampling, potting trials and bulk procurement.
IOTA FLSR3400 addition-type liquid fluorosilicone rubber
