Durometer

In practice

Testing follows ASTM D2240. A durometer callout alone does not define a compound, so specify the polymer and grade too.

Where it comes up

• Rubber extrusion and moldingSeals, gaskets, grommets, and profiles extruded or molded in EPDM, silicone, nitrile, neoprene, FKM, and TPE.
• Urethane castingProduction-like plastic and rubber parts cast in silicone molds, typically 10–200 parts in one to two weeks.

Related terms

Compression set

Compression set is the permanent deformation left in a rubber part after it is held compressed for a set time and temperature, expressed as a percentage of the original deflection. Lower is better for seals and gaskets. It is typically tested per ASTM D395 Method B.

Extrusion die

An extrusion die is a hardened steel plate with an opening shaped to the profile being extruded. Rubber, plastic, or aluminum is forced through it to form continuous lengths. Rubber profile dies typically cost a few hundred to a few thousand dollars and are quick to modify.