Why Solid Rubber and Foam are Ideal Gasketing Materials
Both foam and rubber materials have physical properties that make them ideal for gasketing applications. Unlike metal, composite, or plastic gaskets, these materials can be compressed to fit rough and uneven surfaces, creating a tighter seal. Ensuring a positive seal through material compression is just one key benefit. Foam and rubber gasket materials are used across manufacturers in many industries due to their versatility, utility, ubiquity, and best of all the ease with which they can be converted to the exact part specifications required.
Why is Closed Cell Foam an Ideal Gasket Material?
There are many ways to classify foam materials. One of the major ways to differentiate foam is by how the cells are structured. More specifically, it separates foam types into one of two categories: open cell and closed cell.
Open cell foams, as their name implies, have a cell structure that is porous. Inflating agents which outgas in the manufacturing process create interlocking open pores which create the foam structure. This structure often can make the foam highly compressible and resilient, but it also allows for more absorption and permeation of gas, vapor, and water. This makes open cell foams with high porosity great at cushioning, insulating, and filtration rather than sealing against moisture intrusion. Two-pound polyurethane ester foam is an example of a very widely used porous open cell foam that is breathable to air, vapor, and liquids. These types of open cell products should not be used for liquid intrusion. However, there are microcellular high density open cell foams that can act as a suitable gasket and a water seal if they are compressed enough to stop liquid flow. Products like PoronTM and 3MTM AeroTM IsolossTM are open cell products that can seal against both air and water if designed properly, yet due to their open cell structure, they are typically used for their resilience, vibration damping and insulative properties.
Closed cell foams, on the other hand, have an internal cell structure that remains unconnected within the material because the gas bubbles of the inflating agents remain trapped during the manufacturing process. This allows the foam to be impervious to air, vapor, and water penetration and resistant to liquid absorption. Closed cell foams are available in a wide variety of material types, compression characteristics, and thicknesses. Given the wide variety of options, it is very likely that there is a suitable material for your application and its environment. You are generally able to find a foam material that has the:
Compression deflection and compression set necessary to create the perfect seal
Right thickness to fill the gap in your application
Ideal resistances to environmental factors (including heat, oil exposure, outdoor elements, etc.)
Resistance to chemicals
Resistance to mold and fungi
Resistance to weather and UV light (i.e., EPDM)
Temperature resistance (i.e., silicones)
Typical closed cell foam gasket options include:
Why is Solid Rubber an Ideal Gasket Material?
Other suitable choices for many gasketing applications are the many different types of rubber. Rubber is a tough and durable material that has high shock absorption and impact and abrasion resistance. The material seals out liquid and moisture, and the variety in polymer types allows for a material to be chosen that meets specific application requirements. An important method of classifying solid rubber is by its hardness or durometer which is measured on the Shore A scale. Lower numbers, like the 20D rubber commonly seen in rubber bands are soft rubbers. Moving up the scale, 40D rubber like that seen in pencil erasers are medium soft, 70D rubbers seen in car tires are medium hard, and 90D rubber like that in hockey pucks are categorized as hard.
Since rubber is an elastomer, the material is conformable to surfaces and under compression and can create a tight, resilient seal. Compared to closed cell foam gaskets, solid rubber is much less compressible, especially as durometers increase, so it is critical to pay close attention to the product and gasket design tolerances to ensure a proper seal.
Rubber is also a very stable material and can be engineered to resist many types of harsh environmental conditions that include:
Acids
Alkalis
Oxidation
Ozone
UV light
Water (hydrolysis)
High temperatures and flames
Electricity
The resistances that different types of rubber have depend on the base compounds used during the manufacturing process. Rubber materials also come in various thicknesses that can be die cut and fabricated to allow them to fit any space in any application.
Typical rubber gasket options include:
The Industry Applications Examples of Foam and Rubber Gaskets
Automotive drive flange oil gasket
Electrical enclosure door seals
Medical hearing aid moisture protection
HVAC Roof Unit drip pan seal
Electric vehicle battery seal
Commercial lighting seal
Customize Rubber and Foam Gaskets
Whether you choose rubber or foam gaskets, Engineered Materials can help you customize the materials to fit your application. We offer foam and rubber materials in a variety of thicknesses, all of which can be combined with PSA tapes for a secure bond and tight fit. Combining gaskets with PSA tape allows you to reliably bond dissimilar materials, creating an air or watertight seal that is effective and easy to install.
Looking for help with gasket material selection, conversion, fabrication, and anything else? We have it all in-house. Contact us today to talk about your gasketing application today.