Material that can be deformed elastically, that is it can be stretched to a significant extent and after relief it will quickly and practically completely return to its initial shape. Elastomers comprise more or less loosely linked thread molecules. This linking keeps the threads of molecules together during stretching and prevents the transition to the plastic state on the addition of heat. Unlike thermoplastics, elastomers can therefore no longer melt, instead they are broken down chemically if the maximum permissible temperature is exceeded.
The degree of linking defines the hardness of the elastomer: The more the material is linked, the harder it becomes.
The most important materials for seals in this group are:
- NBR (acrylic nitrile butadiene): It has good mechanical properties including abrasion resistance. It can be adapted to different tasks by varying the acrylic-nitrile content. Temperature range between -20° and +100°C.
- FKM (fluorinated rubber) has high resistance to mineral oil and HFD fluids even at high temperatures (up to 200°C).
- FVMQ (fluorosilicone rubber) can be used over a very high temperature range, high resistance to swelling in relation to mineral oils.