Sponge rubber gaskets vs. solid rubber gaskets is a comparison that many seal designers need to make. Elasto Proxy can help.

Do you need sponge rubber gaskets for your next sealing and insulation project? Are you sure you don’t need solid rubber gaskets instead? Both types of rubber come in the same compounds, such as EPDM, silicone, nitrile, and neoprene. Sponge rubber and solid rubber can be extruded into the same shapes, and they can be molded into the same sheet sizes, too. In addition, both types of rubber support the same fabrication processes, such as water jet cutting and adhesive taping. 

So what’s the difference between sponge rubber and solid rubber, and how does it affect the seal design process? Ultimately, the difference is about air. Sponge rubber materials contain interconnected pockets that either hold air (closed cells) or permit its passage (open cells). Solid rubber materials don’t  have this cellular structure. Sponge and solid rubber both provide sealing and insulation, but sponge rubber provides better cushioning while solid rubber provides greater impact resistance.  

If you’re an engineer who’s looking for a custom sealing solution, Elasto Proxy can help you to compare sponge rubber gaskets vs. sponge rubber gaskets for your specific application. Elasto Proxy is both a rubber fabricator and a rubber distributor, and we keep plenty of sponge rubber profiles and solid rubber profiles in stock at our North American and European warehouses.

Keep reading to learn more or request a quote.   

ES32-062-E70 is a U-shaped, 70-durometer, solid rubber profile that is made of EDPM.

Solid Rubber Gaskets

Solid rubber gaskets are fabricated from materials that combine dimensional stability with high tensile strength. They are more resistant to compression than sponge rubber profiles, but that doesn’t mean solid rubber is always hard. Consider the difference between a pencil eraser and a hockey puck. Both are made of solid rubber, but a pencil eraser compresses if you pinch it. That’s not the case with a hockey puck, especially if it’s been kept on ice.

Durometer, a measure of hardness, lets us put numeric values to these differences. As a rule, lower durometers are softer and higher durometers are harder. For example, the soft rubber in a pencil eraser has a durometer of 40 on the Shore A scale. The hard rubber in a hockey put has a durometer of 90 Shore A instead. Hardness is important, but it’s not the only way in which solid rubber gaskets differ from each other and from sponge rubber.    

In addition to durometer, engineers may need to consider density and force distribution. Denser rubber offers greater resistance to abrasion and wear. It is stiffer and less elastic but can better withstand applied forces. Tear resistance, another material property, describes the resistance of an elastomer to the development of a cut or nick when tension is applied. Tensile strength, the amount of force needed to tear apart a rubber specimen, and temperature range are also key specifications.

EC12-545-EMT1 is a medium-durometer EPDM sponge rubber profile.

Sponge Rubber Gaskets

Sponge rubber gaskets also come in different durometers. They’re usually softer than solid rubber gaskets, but that’s not always the case. If you’re comparing these two types of materials, remember that a 40-durometer sponge rubber gasket is still harder than a 30-durometer solid rubber gasket. Also, while sponge rubber provides better cushioning, seal failure can occur if the gasket is over-compressed. That’s because rubber is resilient, but only to a point.  

Compressing a rubber gasket within an allowable percentage causes a seal to form. The ideal compression percentage is 40, the maximum is 50, and the minimum is between 10 to 15. If a gasket is compressed by more than 50%, however, it might not return to its original size. In other words, the rubber won’t rebound or “bounce back” when the compressive stresses are removed. This creates a gap between the rubber gasket and the substrate, such as the edge of the door, through which leakage occurs.  

This problem is called compression set, and it can happen to (but is not limited to) sponge rubber. Compression set can happen to solid rubber gaskets as well, but solid rubber is typically (though not always) harder and more resistant to compression. Where sponge rubber differs from solid rubber is its cellular structure. If the sponge rubber’s cells are open and the gasket is not compressed, air and water can pass. If the cells are closed, then the passages are also closed.  

Abrasive Water Jet Cutting Services
Elasto Proxy uses pure water jet cutting and abrasive water jet cutting equipment.

Solid Rubber Gaskets vs. Sponge Rubber Gaskets Simplified

Do you need low-to-medium volumes of custom gaskets for applications such as sealing the doors and windows on heavy equipment? Maybe you need help with enclosure sealing on food equipment, generator sets, or industrial machinery instead. Elasto Proxy can help you to get the rubber gaskets that you need and has 30+ years of experience that we can leverage on your behalf. From design assistance to material selection to value-added manufacturing, we invite you to learn more about us and the difference that having a true manufacturing partner can make.

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