SilMaterials in Aerospace

Silicon Materials in Aerospace

Aerospace silicone applications combine the most demanding service conditions in the silicone industry — temperature extremes from -65 °C to +250 °C continuous, high-altitude UV and radiation exposure, vacuum service, multi-decade reliability requirements, and stringent outgassing and flammability standards. Silicones are the dominant elastomer choice across most aerospace categories.

Major Application Categories

Engine and propulsion seals: phenyl-modified HTV silicone for compressor stage seals, accessory drive seals, and hot-section gaskets. Service: 200-250 °C continuous. Fluorosilicone (FVMQ) for fuel-system O-rings and fuel-line connectors where hydrocarbon resistance combined with low-temperature flexibility is required.

Cabin and structural seals: door perimeter seals, window glazing seals, cargo door seals, and structural-glazing applications. Standard HTV silicone with low-temperature additives.

Wing and surface controls: silicone elastomer in flap seals, slat seals, and aileron seals. Service temperatures cycle from -55 °C high-altitude to +85 °C ground-park sun exposure.

Avionics encapsulation: low-outgassing silicone gels (TML below 1.0%, CVCM below 0.1% per ASTM E595) for avionics box potting, sensor encapsulation, and circuit-card protection. Critical for spacecraft and high-altitude UAV applications.

Ablative and thermal-protection coatings: silicone-modified ablative coatings for re-entry vehicle and missile leading-edge thermal protection. The silicone carbonizes during ablation, leaving a silica char that insulates the underlying structure.

Satellite-grade encapsulation: ultra-low-outgassing platinum-cured silicone gels for satellite electronics. Specifications target below 0.1% TML for sensitive optical components.

Specifications and Standards

Aerospace silicone selection is governed by:

• MIL-STD-810: environmental engineering considerations and laboratory tests
• MIL-PRF-46170: silicone elastomer technical data
• MIL-PRF-23586: corrosion-prevention compounds
• NASA-PRC-2000 / ASTM E595: outgassing requirements (TML, CVCM, WVR)
• ASTM E162: flame propagation of materials
• DO-160: environmental conditions and test procedures for airborne equipment
• AS 9100: quality management for aerospace; supplier-side requirement

Aerospace qualification cycles can take 5-10 years per platform; once qualified, silicone formulations remain in service across decades.

Sourcing Considerations

Aerospace-grade silicones are supplied by a concentrated set of producers with dedicated aerospace-grade production lines:

• NuSil Technology (now Avantor): the dominant aerospace-grade silicone supplier; multiple low-outgas platinum-cured products
• Dow Silicones (Dow): Silastic aerospace grades and dedicated Q7 / Q8 series for satellite applications
• Wacker Chemie: ELASTOSIL and LUMISIL aerospace product family
• Shin-Etsu: KE-1300 and KE-2000 series with aerospace certifications
• Momentive: aerospace-grade adhesives and encapsulants

Chinese aerospace-grade silicone production is emerging but supplier qualification cycles for aerospace platforms are long; Western supply remains dominant for premium aerospace and space applications.

Related Reading

Silicone rubber category, High-temperature resistance, Low-temperature flexibility, Encapsulation application.