There is a close relationship between the hardness and temperature of an o-ring, as temperature changes directly affect the hardness and modulus of elasticity of an elastic material. Hardness is a mechanical property of an elastic material that describes the material's resistance to external forces.
In general, the relationship between O-ring hardness and temperature can be summarized as follows:
Hardness decreases with increasing temperature:
As the temperature increases, the hardness of most elastomeric materials generally decreases. This is because at high temperatures, the thermal motion of the molecules increases, resulting in a more susceptible change in the molecular structure of the material, which affects the hardness.
Hardness increases with decreasing temperature:
At low temperatures, some elastomeric materials may become more brittle and may increase in hardness slightly. This is because the movement of the molecules is slowed down at low temperatures, and the molecular structure is more stable, which affects the hardness.
Effect of hardness on tightness:
The hardness of an O-ring directly affects its sealing performance. In some applications, changes in temperature can cause changes in the hardness of the o-ring, which in turn can affect its tightness. At high temperatures, too soft o-rings may lose their elasticity, while at low temperatures, too hard o-rings can become brittle, both of which can lead to a decrease in sealing performance.
Hardness & Material Selection:
In a high or low temperature environment, it is important to choose the right hardness for the o-ring material. Typically, o-rings with a hardness range between 50 and 90 Shore A are commonly used in general industrial applications.
Engineering Material Selection:
In a high-temperature environment, some special engineering materials, such as silicone rubber, have good high-temperature stability and can maintain a certain hardness. At low temperatures, materials such as fluoroelastomers may be more suitable because they retain good elasticity at low temperatures.
In practice, manufacturers often provide data on the hardness and performance of O-ring materials at different temperatures. Choosing the right hardness for an o-ring should take into account the range of temperature variations, the operating environment, and the desired sealing performance.