In addition to meeting the general requirements for sealing ring materials, sealing rings should also meet the following conditions:
(1) Possessing good elasticity and resilience;
(2) Appropriate mechanical strength, including tensile strength, elongation, and tear strength;
(3) Stable performance, not easily swelling in the medium, and minimal thermal shrinkage (Joule effect);
(4) Easy to process and mold, and able to maintain precise dimensions;
(5) Non-corrosive to contact surfaces and does not contaminate the medium.
The most suitable and commonly used material that meets the above requirements is rubber, therefore, most sealing rings are made of rubber. There are many types of rubber, and new types are constantly emerging. When designing and selecting, the characteristics of various rubbers should be understood to make a reasonable choice.
As one of the most commonly used sealing methods, O-rings possess the following comprehensive performance characteristics: Advantages include excellent sealing performance and long service life; small size, light weight, and low cost; simple sealing structure and easy assembly/disassembly; a single ring can provide sealing in two directions; good adaptability to oil, temperature, and pressure; suitable for both static and dynamic sealing; low dynamic friction resistance; and standardized dimensions and grooves, facilitating selection and external procurement. Disadvantages include relatively high frictional resistance during dynamic sealing startup, approximately 3-4 times the dynamic friction force, and the tendency to be squeezed into gaps under high pressure; the need for lubrication when used as a seal in pneumatic devices to prevent wear; and stringent requirements for the machining dimensions and precision of mating components such as moving surfaces, grooves, and gaps.
