Elastomerics Blog

Silicone foam and silicone sponge are both lightweight, compressible elastomeric materials that provide environmental sealing, cushioning, and thermal insulation. The main difference lies in their cell structure and mechanical properties—silicone sponge has a closed-cell structure and higher toughness for harsh outdoor sealing, while silicone foam offers softer compression and flame-rated indoor cushioning. Stockwell Elastomerics fabricates both materials into precision gaskets, pads, and tapes at its Philadelphia facility.

What Are Silicone Foam and Silicone Sponge?

Silicone foam and silicone sponge are both cellular silicone materials – expanded forms of solid silicone rubber containing internal air pockets. These materials combine silicone’s inherent high-temperature stability and weather resistance with the compressibility and conformability needed for reliable gasket and cushioning performance.

Stockwell Elastomerics stocks and fabricates both materials into custom die-cut, waterjet-cut, and adhesive-laminated parts. They are widely used across aerospace, electronics, medical, defense, and industrial equipment where long-term resilience and consistent sealing under compression are critical.

How Do Cellular Structures Differ?

The most fundamental difference between silicone foam and silicone sponge lies in their cellular structure.

Silicone sponge has a closed-cell structure, meaning the internal air pockets are completely enclosed. This prevents water or air from passing between cells, making silicone sponges an excellent choice for environmental or weatherproof sealing, especially in harsh outdoor enclosures, NEMA-rated housings, and wash-down environments.

Silicone foam, on the other hand, can be open-cell or partially closed-cell depending on its density. Lower-density or open-cell foams contain more interconnected cells, allowing limited air and moisture movement. Higher-density foams have more closed cells, improving their resistance to water ingress. When compressed approximately 50–70%, even open-cell foams can achieve a durable seal against weather and dust.

Both materials are expanded silicone elastomers, but foam manufacturing allows for more control over density and compressibility, providing engineers with options for different load bearing or deflection requirements.

How Do Compression and Recovery Compare?

Silicone sponge and silicone foam both demonstrate excellent compression set resistance, meaning they recover their original thickness after prolonged compression. Their cellular structures allow them to deflect easily under low compressive force, making them suitable for sealing lightweight assemblies without damaging sensitive components. Both materials require at least 50% compression for optimal sealing, ensuring continuous contact pressure and maintaining the seal.

Which Material Performs Better at Temperature Extremes?

Silicone sponge and silicone foam both exhibit the outstanding temperature stability that defines silicone materials. However, temperature performance is a key differentiator:

• Silicone Sponge: Operates from -100°F to +500°F (-73°C to +260°C)
• Silicone Foam: Operates from -67°F to +392°F (-55°C to +200°C)

Silicone sponge’s broader temperature range and greater mechanical toughness make it ideal for outdoor exposure, dynamic sealing, and harsh mechanical environments. Silicone foam, while slightly softer and less rugged, offers a more uniform cell structure that performs exceptionally well in cushioning, insulation, and vibration-damping roles.

When Should You Choose Silicone Foam vs. Silicone Sponge?

Both materials provide UV, ozone, and weather resistance, but their best-fit applications differ based on the required sealing and mechanical properties.

Silicone Sponge is preferred for:

• Outdoor weatherproof gaskets and NEMA enclosures (telecom, instrumentation and control systems)
• Wash-down environments (food processing, industrial equipment)
• Cryogenic and high-temperature sealing (commercial ovens, aerospace systems)
• Rugged mechanical interfaces requiring high tear strength and durability

Silicone Foam is selected for:

• Indoor gasketing and cushioning where compressibility and softness are key
• UL 94 HF-1 or V-0 flame-rated enclosures (lighting, displays, electronics)
• Touchscreen gaskets and vibration damping in portable or handheld devices
• LED lighting housings and instrumentation panels where lightweight seals are required

In short, silicone sponge excels when water sealing and mechanical toughness are critical, while silicone foam is ideal when low compression force, flame resistance, or soft cushioning are design priorities.

Stockwell Elastomerics’ In-Stock Materials and Fabrication Capabilities

Stockwell Elastomerics maintains a deep inventory of premium silicone foam and sponge materials from trusted suppliers, including:

• Saint-Gobain NORSEAL® Silicone Sponge and Foam – available in general-purpose and spec-grade formulations.
• Rogers BISCO® Silicone Foam – featuring precise density control and consistent flame ratings for electronics and transportation applications.

Both materials can be die-cut, waterjet-cut, flash-cut, slit, or laminated with pressure-sensitive adhesives in Stockwell’s Philadelphia manufacturing facility.

Choosing the Right Material for Your Design

Selecting between silicone foam and silicone sponge often depends on your application’s environmental exposure, temperature range, and compression requirements.

• Choose silicone sponge when sealing against liquids, dust, or outdoor conditions.
• Choose silicone foam when lightweight, low-force, or flame-rated sealing is needed.

Stockwell Elastomerics’ applications engineering team can assist in evaluating materials for performance, manufacturability, and compliance with standards such as UL 94, ASTM D1056, and MIL-DTL-25988.

Request a Rapid Silicone Gasket Sample Today

Stockwell Elastomerics is a leading U.S. manufacturer of precision silicone gaskets, foam pads, and EMI shielding components. Our team combines material science expertise with advanced fabrication to deliver custom-engineered silicone foam and sponge parts for demanding environments.

Contact Stockwell Elastomerics to request a technical consultation, samples or more information.