Specifications for rubber or elastomeric gasket materials often reference an ASTM classification. For example, silicone gasket sheet material might be shown as “ISO/ASTM Designation FE” while material for a nitrile gasket could be BF. These references come from ASTM D2000, one of many standards addressing gasket design, gasket material and gasket classification. Buyers don’t have to know these standards, but understanding what they address helps when selecting material.
ASTM and their gasket standards
ASTM International develops voluntary consensus standards. These help manufacturers and buyers alike by standardizing aspects of design, testing and manufacture.
For gasket materials the first two standards to be aware of are F104 and D2000. F104 is a system for classifying non-metallic gasket materials. The idea is to simplify material and gasket selection by translating application needs into a six digit code. F104 covers asbestos, cork, cellulose, PTFE, graphite and other non-asbestos materials. Rubber and rubber-like materials are excluded from this system and come under D2000 instead.
Material properties like compressibility and tensile strength are covered under a range of other standards. For example, D2240 addresses testing of rubber hardness, (durometer,) while F36 describes compressibility and recovery and F37 covers sealability test methods.
Interpreting ASTM classifications
The D2000 standard does the same for vulcanized rubber as F104 does for non-metallic gasket materials, namely, it sets out a standard way of describing every type of material. A complete D2000 specification covers maximum temperature, swelling performance, hardness and tensile strength, plus optional characteristics such as fuel and water resistance.
Maximum temperature is defined as the temperature at which material performs degrades to a set level. This is indicated by letter where “A” means a maximum of 70°C and K is 300°C. Swelling performance is also shown by letter with B the highest.
These two letters are used to describe many rubber-like materials. A “FE” designation for silicone gasket material shows that it’s performance degrades only slightly at 200°C but under defined conditions it will swell by 60%. Likewise, a nitrile gasket designated “BF” has the same swell behavior but is only good to 100°C.