Silicone Products Silicone Sponge Cords

What Are Silicone Sponge Cords?

Silicone sponge cords are round, closed-cell extruded silicone profiles used for sealing, gasketing, cushioning, vibration isolation, and gap filling. Their lightweight, compressible construction allows them to conform to curved surfaces and irregular spaces while providing environmental protection and reliable performance across a wide temperature range.

Bellofram Elastomers manufactures custom silicone sponge cord in diameters ranging from 0.062” to 2.5”. Available in multiple hardnesses and custom lengths, our closed-cell silicone sealing cords are designed for applications requiring flexibility, compression recovery, moisture resistance, and long-term durability.

Key Takeaways

• Silicone sponge cord is a round, closed-cell extrusion designed for sealing, gasketing, cushioning, and gap filling.
• Available in diameters from 0.062” to 2.5”.
• Bellofram Elastomers offers materials across all five ASTM D1056 hardness ranges.
• Closed-cell construction helps resist water absorption and prevent wicking.
• Designed to perform from -85°F to +400°F.
• Provides resistance to UV, ozone, environmental exposure, and compression set.
• Available in standard or custom lengths.
• Qualified options are available for Boeing BMS 1-23 and all three hardnesses of BMS 1-60.
• Ideal for aerospace, defense, transportation, industrial equipment, and environmental sealing applications.

Why Choose Closed-Cell Silicone Sponge Cord?

Silicone sponge cord combines the flexibility of silicone with a lightweight cellular structure that compresses easily to create an effective seal.

Its round profile makes it particularly useful for filling gaps, following curved surfaces, and creating custom seals.

Benefits of Silicone Sponge Cords

BENEFIT	WHY IT MATTERS
Closed-Cell Construction	Helps resist water absorption and prevent wicking in moisture-prone sealing applications.
Flexible Round Profile	Conforms easily to curved surfaces, irregular gaps, and custom sealing paths.
Lightweight and Compressible	Provides effective sealing and cushioning without adding unnecessary weight or requiring excessive closure force.
Wide Temperature Range	Maintains performance from -85°F to +400°F across demanding hot and cold environments.
Environmental Resistance	Silicone provides resistance to UV, ozone, and outdoor exposure for long-term sealing performance.
Multiple Hardness Options	Material can be selected from all five ASTM D1056 hardness ranges to match compression and sealing requirements.
Custom Sizing	Diameters from 0.062" to 2.5" provide flexibility for both small precision seals and large gap-filling applications.

Silicone Sponge Cord Size and Material Options

Bellofram Elastomers manufactures silicone sponge cord in a wide range of diameters and hardnesses to support different sealing, cushioning, and compression requirements.

Silicone Sponge Cord Options

OPTION	AVAILABLE CAPABILITY
Profile	Round closed-cell silicone sponge cord.
Diameter Range	0.062" to 2.5".
Hardness	Available across all five hardness ranges specified by ASTM D1056.
Temperature Range	-85°F to +400°F.
Lengths	Available in standard or custom lengths.
Aerospace Specifications	Qualified options available for Boeing BMS 1-23 and all three hardnesses of BMS 1-60.
Custom Manufacturing	Elastomer, color, length, and other material characteristics can be tailored to application requirements.

Silicone Sponge Cord vs. Solid Silicone Cord

The primary difference between silicone sponge cord and solid silicone cord is material structure. Silicone sponge cord contains a closed-cell structure that makes it lighter and more compressible, while solid silicone cord provides a denser, non-cellular construction.

Silicone Sponge Cord vs. Solid Silicone Cord

FEATURE	SILICONE SPONGE CORD	SOLID SILICONE CORD
Construction	Closed-cell silicone sponge.	Dense, silicone rubber.
Density	Lightweight.	Denser and heavier.
Compression	Highly compressible and suited for lower closure-force sealing.	Less compressible and typically requires greater force to deform.
Gap Filling	Well suited for irregular gaps and surfaces requiring a conformable seal.	Better suited where dense rubber strength and firmness are required.
Typical Priority	Cushioning, compression sealing, lightweight performance, and environmental protection.	Dense sealing, durability, mechanical strength, and dimensional stability.

For applications requiring a dense, non-cellular round extrusion, explore our Silicone Cords.

Common Applications for Silicone Sponge Cords

Silicone sponge cords are used where a flexible round extrusion can provide sealing, cushioning, insulation, or vibration isolation.

Common Applications for Silicone Sponge Cords

APPLICATION	HOW SILICONE SPONGE CORD HELPS
Enclosure Sealing	Compressible cord fills gaps around doors, covers, and access panels to help protect against moisture and contaminants.
Curved-Surface Sealing	The round flexible profile follows contours and irregular geometries more easily than rigid sealing components.
Custom Gaskets	Cord can be cut to length or fabricated into custom gasket configurations.
Gap Filling	Compressible sponge construction fills uneven or variable spaces while maintaining sealing pressure.
Vibration Isolation	Cellular silicone helps cushion components and reduce vibration transmission.
Thermal and Environmental Protection	Wide temperature capability and resistance to UV and ozone support use in demanding environments.
Aerospace and Transportation	Qualified material options support applications requiring traceability, environmental resistance, and Boeing material specifications.

Aerospace-Grade Silicone Sponge Cord

For aerospace, defense, and transportation applications, material qualification and repeatability can be just as important as dimensional performance.

Bellofram Elastomers is listed on the qualified products list for Boeing BMS 1-23 and is approved for all three hardnesses of BMS 1-60. These qualifications make Bellofram silicone sponge cords a strong option for applications requiring documented material compliance and reliable performance.

Our in-house mixing and compounding capabilities also provide control over material properties and consistency from batch to batch.

Custom Silicone Sponge Cord for Gaskets and Seals

Bellofram Elastomers can tailor silicone sponge cord to meet specific diameter, hardness, length, compression, and performance requirements.

Because round cord can be easily cut to length and adapted to different sealing paths, it provides a versatile alternative to more complex extrusion profiles when a simple circular geometry can meet the application’s needs.

Silicone sponge cord may be used as:

• Continuous sealing cord
• Cut-to-length seals
• Custom gasket material
• Enclosure seals
• Insulation components
• Vibration-isolation elements
• Environmental seals
• Gap-filling material
• Cushioning components

For more complex cross-sectional shapes, explore our Silicone Sponge Profiles.

For hollow round configurations requiring greater compressibility, explore our Silicone Sponge Tubing.

When Should You Choose Silicone Sponge Cord?

Silicone sponge cord may be the right choice when your application requires a simple, flexible round seal that can compress and conform to irregular spaces.

Silicone sponge cord may be ideal when:

• A round sealing profile fits the application.
• Irregular gaps or curved surfaces must be sealed.
• Low closure force is important.
• Moisture absorption and wicking must be minimized.
• The component must perform from -85°F to +400°F.
• UV, ozone, or environmental exposure is expected.
• Different hardness levels are needed to optimize compression.
• Aerospace material qualifications such as BMS 1-23 or BMS 1-60 are required.
• Custom diameters or cut lengths are needed.

Why Choose Bellofram Elastomers for Silicone Sponge Cords?

Bellofram Elastomers combines in-house silicone compounding and extrusion capabilities to provide custom silicone sponge cords with controlled material properties and consistent dimensions.

Bellofram Elastomers offers:

• Diameters from 0.062” to 2.5”.
• All five ASTM D1056 hardness ranges.
• Closed-cell silicone sponge construction.
• Temperature performance from -85°F to +400°F.
• UV, ozone, and compression-set resistance.
• Standard and custom lengths.
• Boeing BMS 1-23 qualified material.
• Approval for all three BMS 1-60 hardnesses.
• Custom compounding and extrusion support.
• U.S.-based manufacturing in Newell, West Virginia.

Frequently Asked Questions About Silicone Sponge Cords