sponge gaskets
At NEDC, we commonly offer different gasketing solutions. Many in the industry organize cellular products in their head a few different ways. However, the specification ASTM D1056 organizes them by type, class, and then grade. Most of the materials characteristics can then be called out within three characters. This is just a summary of the specification, there are details of how to test, and what to test to located within the specification. Many other specifications either reference ASTM D1056 for its definitions and testing. It is largely seen as the authority on cellular products in the gasketing industry.
Type
There are two “types” 1 or 2. 1 indicates open-cell sponge, while 2 indicates closed-cell sponge. This indicates to the user how well the sponge material needs to be able to resist absorbing water. Type 2 must be less than a 5% absorption for densities over 10 pcf, and 10% for 10 pcf and less. Anything else is considered open cell sponge.
Class
A, B, C, D. These classes indicate different requirements of the material. This is probably where the variations really begin. For example, Class A indicates it is non-oil resistant. Many materials could meet this requirement. However, the other classes provide more stringent requirements.
Class A- Non-Oil Resistant
Class B- Fuel-Resistant, Low-Mass Change
Class C- Fuel Resistant, Medium-Mass Change
Class D- High-Temperature Resistance
Class A
As mentioned before, many different materials could meet Class A as that is a low-bar to clear. Oftentimes, sponge blends are found in this class as blending many properties of polymers can achieve a great product, but can have drawbacks when it comes to fuel-resistant requirements. Polymers such as SBR, Natural Rubber, and EPDM are commonly found in this class of materials. It is common for some materials that meet other requirements to meet this as well. For example, 2C1C1F1 technically meets 2A1C1F1- because the Class A is NO REQUIREMENT, so C is better.
Class B
Class B is the most stringent requirement for fuel resistance in the spec. This is typically where you will find epichlorohydrin(ECH), nitrile(buna-n), and other polymers that are very resistant to fuel.
Class C
Class C usually has a host of Neoprene Sponge materials in this class. Neoprene has great resistance to oil. Typically these are not blends, and if they are they contain a very high content of Neoprene Sponge.
Class D
Class D is high-temperature resistance. This is where you will find your high-temperature resistant polymers such as silicone sponge. Silicone sponge is the go-to in the industry for high-temperature resistance while featuring lower compression set.
Grade Classifications
This characteristic indicates the compression/deflection of the sponge material. The higher the number, the more force is required to compress it 25%. The available grades are 0-5. 0 indicates 0-2 psi, while 5 indicates 17-25 psi, with other grades in between 0 and 5. Take the example of 2A0 super-soft would be considered a Grade Classification 0 for super-soft- or say 2A5 would be firm. Different polymers are more challenging than others to achieve a specific density while meeting other requirements. While they aren’t perfectly correlated, higher density of the sponge/foam material is usually associated with higher compression/deflection requirements.
Is ASTM D1056 Foam, or Sponge?
The difference between sponge, and foam is pretty nuanced- however for all intents and purposes- you can call these materials either- ASTM D1056 covers both foam/sponge. The more important distinction to make is when it comes to the thickness tolerance of Expanded Rubber, or Sponge Rubber- but of these materials are made slightly differently- but to be honest, it all depends on your application.
Additional Suffixes
Within ASTM D1056 there are other requirements that can be specified by suffixes. These suffixes are indicated by letters, A through W. Z indicates a special requirement that is not located in the specification. Oftentimes, Z equals Fungus Resistance for military programs, such as MIL-STD-810 METHOD 508, Classification 1 or 0.
hvac system, foam application
hvac system, foam application
Color, Its Always Black?
These materials come in a standard color of black unless otherwise specified- given most of these organic polymers foam/sponge were already black due to the carbon black fillers. However, silicone sponge is oftentimes provided in the standard rusty-red.
Example of an Application of ASTM D1056
Lets start with an easy one.
2A1, 2= closed cell, A= no class requirements, 1= Soft (2-5 psi)
Now how about a hard one?
2C1A2B3C3F1MZ, Z= fungus resistance per MIL-STD-810 METHOD 508. Thats a mouth full!
2= closed cell, C= C class requirements, oil expansion during immersion, 1= soft, A2=compression/deflection after temperature aging, B3= compression set requirements 35% max, C3= ozone exposure Method B, F1= low-temperature flexibility, Mfire combustion characteristics, Z= fungus resistance as stated..
Keep in mind some of these classes, grades, types, suffixes, are mutually exclusive of each other- you cannot combine all of them all of the time.
More Information / Additional Questions on ASTM D1056
NEDC offers die-cutting, and waterjet cutting of cellular sponge products materials. For more information on ASTM D1056 or sponge gaskets, or you believe you have an application that could utilize them, please contact sales@nedc.com.