Custom EPDM gaskets are made of extruded or molded EPDM rubber and fabricated into seals and insulation. They are cut from sheets and profiles of solid, sponge, or foam materials that come in commodity and specialty grades. In addition to water jet cutting, EPDM supports bonding or splicing for finished gaskets and adhesive taping for peel-and-stick gasket installation.
Custom EPDM gaskets are a great choice for environmental sealing. They provide good thermal and electrical insulation, too. Yet this type of custom rubber gasket won’t withstand petroleum products or concentrated acids. Before choosing EPDM gaskets then, you need to understand their rubber properties. You also need to know about the different types or grades of EPDM that are available.
Advantages and Disadvantages of EPDM Rubber
Ethylene propylene diene monomer (EPDM) resists sunlight, ozone, oxygen, aging, acids, alkalis, water, and severe weather conditions. This odor-free elastomer also provides excellent color stability and high heat resistance. Typically, service temperatures range from -70° C to 250° C. All EPDM rubber isn’t the same, so differences in ethylene content and the dienes that are used can affect physical properties.
EPDM generally provides good tensile strength and elasticity. Tensile strength, the resistance to breaking under tension, is measured in pounds per square inch (PSI). With EPDM, typical values are in the 1000 PSI range. Elasticity, a measure of a material’s ability to resume its normal shape after being stretched or compressed, is expressed as a percentage. With EPDM, this percentage is typically in the 300% range.
The main disadvantage of EPDM is its unsatisfactory resistance to certain categories of chemicals. In addition to gasoline, diesel fuel, and motor oil, EPDM is not recommended for use with synthetic diester oils, lubricants found in some types of industrial machinery. EPDM also provides unsatisfactory resistance to Freon, a category of fluorocarbons that are used as refrigerants.
Custom EPDM seals are sometimes used instead of silicones, nitriles, or thermoplastic elastomers (TPEs). Silicones can withstand lower and higher temperatures, but they lack EPDM’s resistance to abrasion, cutting, and tearing. EPDM also provides better tensile strength. For resistance to fuels, greases, and oils, nitrile is a better choice. TPE costs more than EPDM rubber but is recyclable.
Types and Grades of EPDM Gasket Materials
EPDM rubber is molded into sheets or extruded into profiles with different durometers (hardness). Most EPDM materials have a durometer of 40 to 90 (Shore A). Lower durometer EPDM is softer and provides cushioning but is more prone to compression set, a permanent deformation that can result in seal failure. Higher durometer EPDM is harder and provides impact resistance. It’s like a hockey puck instead of a pencil eraser.
Custom EPDM gaskets are made from either sponge rubber or solid rubber. At its most basic level, the difference is about air. Sponge rubber contains balloon-like cells or interconnected pockets. Open-cell EPDM sponge rubber permits the passage of gases or air. Closed-cell EPDM sponge rubber does not. Solid rubber doesn’t have this cellular structure.
Custom EPDM seals that are made from commodity rubber provide good resistance to hot and cold water, saturated steam, or outdoor environments. Higher-grade EPDM rubber offers enhanced material properties and may be recommended for better compression set. Specialty rubber may be required if your application must comply UL 94 or FDA standards.
UL 94 EPDM gaskets are made of flame-retardant rubber that meets specific burn tests such as V-0, V-1, and V-2. Some compounds are halogen-free. Custom gaskets made of UL-rated EPDM sponge rubber also provide good sealing and moderate-to-good cushioning. FDA-approved EPDM gaskets are used in food contact applications and medical devices. Not all food-grade rubber is FDA-approved, however.
How to Find Custom EPDM Gaskets
Do you need custom EPDM gaskets? Do you have questions about EPDM rubber’s advantages or disadvantages? Are you looking for specific EPDM types or grades? For assistance, contact Elasto Proxy.