#1 What is the restoring force?
The restoring force describes the will of a material to return to its original state after a load.
If a rubber is stretched or compressed, it then wants to return to its original shape. This elastic behavior of rubber is only possible due to its special molecular structure.
The polymer chains of rubber are not arranged in a rigid structure, but are bundled together in a kind of “ball structure”. When rubber is stretched or compressed, its flexible structure gives it enough elasticity to stretch without tearing.
#2 Why is the restoring force important for O-rings?
Only the high restoring force of O-rings makes it possible for them to maintain their sealing effect over a long period of time and even be used several times.
Note: The restoring force of an O-ring material is specified in data sheets under the item “Compression set – (DVR)” listed.
In this test, an O-ring is clamped between two metal plates and exposed to a higher temperature for a longer period of time. The O-ring is then released again and tested to see to what extent the O-ring returns to its original shape.
If the ring were theoretically to return completely to its origin, the compression set would be 0%. If it is permanently severely deformed, the value could be around 50%, for example.
Tip: If an O-ring material has a compression set greater than 50%, it should not be used.