Choosing the Right Closed Cell Foam for Sealing and Gasketing Applications
Selecting the most effective materials for gasketing applications is critical for ensuring the durability, efficiency, and overall performance of each part. Where many companies struggle making the choice when presented with the sheer number of material options available in the market. While many types of plastic, composites, rubber, and foam can technically be used in gasketing applications, closed cell foams stand out for their exceptional sealing properties, making them ideal for a wide range of gasketing applications. What are closed cell foams, and what should you consider when choosing the most suitable type for your specific needs.
What Are Closed Cell Foams?
By their nature foam products are more compressible than higher durometer materials like composites or rubber. Moreover, Closed cell foams are engineered materials whose cells are entirely enclosed within the foam structure. Unlike open cell foams, where the cell walls are “open” and interconnected, thus making the foams permeable to air and water intrusion, closed cell foams have air bubbles packed within the cell structure that provides a foam which is resistant to water, air, and gases, thereby offering exceptional sealing and gasketing capabilities.
Why Closed Cell Foams Excel in Gasketing Applications
While open cell foams (like reticulated foam, etc.) are more suited for filtration applications because they allow gases and liquids to pass freely through them, the inherent physical properties of closed cell foams make them far more suitable for gasketing applications. Closed cell foams are most known for their:
Durability: many close cell foams do not easily break down when exposed to a variety of environmental stresses making them ideal for outdoor and harsh industrial applications. There is a wide range of products, so depending on the need you can find resistance to UV, moisture, chemicals, fuels, oils and more.
Sealing Properties: These materials also have little or no liquid absorption, so they inhibit the passage of fluids and will minimize the intrusion of gases, providing a reliable seal over time.
Compression Deflection Ranges: There is a wide range of compression deflection (foam push back against compression) values which helps engineers find the right values to ensure positive seals for any application.
Temperature Resistance: many closed cell foams can withstand a wide range of temperatures, making them suitable for applications exposed to extreme conditions.
The Role of ASTM D-1056 in Gasket Selection
The ASTM D-1056 standard provides guidelines for the selection of flexible cellular materials like sponge and expanded rubber materials used in gasketing and sealing applications. This standard outline specific criteria for classifying materials based on their performance characteristics, which include cellular structure, resistance to oils, and firmness as measured by compression deflection. Additional information may also be provided through the standard’s suffix letters that can provide useful characteristics information like heat aging, compression set, ozone resistance, low temperature flexibility and more. Referencing this standard can help engineers make informed decisions when selecting a closed cell foam for their gasketing needs.
What to Consider When Choosing a Closed Cell Foam
What makes an ideal closed cell foam for your gasketing application? That’s highly dependent on the specific application you’re working with and the environment it’s in. From the physical properties to the environmental conditions, here are some of the things you should consider:
The Application Area and Thickness: assess the space and thickness constraints within the application to determine the dimensions of your gasket as well as the minimum or maximum thickness of the material.
Sealing Efficiency: alongside material thickness, it is important to evaluate the amount of foam compression needed to achieve a positive seal, taking into account the foam's compression deflection and compression set.
Mechanical Resilience: consider the foam's resistance to fatigue, impact, elongation, and tensile strength based on the mechanical demands of the application.
Color: different foams have varying color options, which can be a consideration for the aesthetics of your product.
Other Standards to Meet: consider any other UL, FR, MIL specs, automotive specs, or FDA requirements.
It’s also important to consider the environmental factors in your application, including:
The exposure to humidity, ozone, UV radiation, and temperature extremes.
The exposure to chemicals, solvents, or fuels the foam may encounter.
The expected lifespan of the application
The need for thermal, electrical, acoustical or vibration insulation. Different foam types have essential qualities that allow them to provide the levels of insulation you need.
What Are Your Closed Cell Foam Gasketing Options?
Polyethylene Foam
Polyethylene foam is a chemically inert closed-cell foam known for its low weight and affordability. It’s durable and impact-resistant properties provides excellent moisture resistance and thermal insulation. It’s also capable of absorbing energy and vibrations effectively. Its buoyancy and non-dusting characteristics make it ideal for spacers, packaging, vibration dampening, and floatation devices.
Strengths: Lightweight and flexible. Good moisture and chemical resistance. Lower cost.
Limitations: Lower durability and high temperature resistance
Neoprene Foam
Neoprene is a foam derived from synthetic rubber that has a balance of flexibility and durability, and provides some resistance to oils, and chemicals. Its cellular structure provides excellent insulation, buoyancy, and vibration damping properties. It’s commonly used in automotive gaskets, marine applications, and as weather stripping.
Strengths: Durable foam with excellent elongation properties. Good chemical resistance.
Limitations: Fair outdoor performance. Lower service temperature.
EPDM Foam
EPDM foam is a stable synthetic rubber suitable for a wide range of temperatures. Its closed-cell structure ensures effective sealing and insulation, making it resistant to water and steam penetration. EPDM maintains its elasticity and flexibility over time, contributing to its longevity. It’s most commonly used in window and door seals, electrical gaskets, copper tubing insulation.
Strengths: Excellent weather, UV, radiation, and ozone resistance. Very good heat resistance.
Limitations: Poor resistance to petroleum-based oils and fuels. Limited shock absorption.
Blended Neoprene, EPDM, SBR Foam
These blended foams bring the best of EPDM and Neoprene foams together. They are some of the best all-purpose foam products for sealing, gasketing, and insulating applications. These foams provide the added benefit of good flammability performance, carrying a UL94HF-1 rating. They are most commonly used in HVAC, appliances, and automotive gasketing and sealing applications.
Strengths: Strong outdoor performance. Very good temperature performance. Good resistance to chemicals.
Limitations: Poor oil and fuel resistance
Vinyl Nitrile Foam
PVC/NBR foams are soft, flexible, and provide very good flammability performance. Many provide UL94-5VA ratings and have some of the broadest resistances to oils and fuels. Often used in the construction industry under brands like Armaflex(R), these products have very good compression set recovery. They are most commonly used in pipe and HVAC insulation applications.
Strengths: Excellent flame properties. Very good fuel and oil properties alongside very good compression set resistance.
Limitations: Lower temperature range. Weak outdoor weathering
PVC Foam
PVC foam is characterized by its excellent chemical stability, flame retardancy, and resistance to moisture, corrosion, and weathering. It offers a unique combination of properties, including mechanical strength and thermal insulation. PVC foam's closed-cell structure ensures that it performs well in sealing and cushioning applications, so it’s often used in HVAC seals and gaskets, automotive gaskets, and electrical enclosures.
Strengths: Good chemical and corrosion resistance, and flame retardancy. High outdoor resistance.
Limitations: Can become brittle in cold temperatures
Silicone Sponge
Silicone Sponge stands out for its remarkable thermal stability and flexibility across extreme temperature ranges, from very low to very high. It is inert, non-toxic, and offers excellent resistance to compression set, UV light, ozone, and weathering. It’s also hypoallergenic, making it suitable for medical and food-grade applications. Silicone foam is commonly used as a high-temperature gasket and in food-grade seals and medical equipment.
Strengths: ideal for high temperatures. Excellent resistance to weathering, solvents, and flame retardancy
Limitations: Higher cost and lower tear strength.
Read more about the differences between silicone foam and silicone sponge when it comes to high temperature gasketing materials.
Make the Best Choice for Your Gasketing Application
Choosing the right closed cell foam involves understanding the unique properties of each foam and considering the specific requirements of the application. Now that you’re armed with technical knowledge and guided by standards such as ASTM D-1056, selecting the ideal closed cell foam is a more straightforward process, and our team at Engineered Materials can help you make the best choice, every time.