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Knowledge of rubber O-rings:

1. Introduction to rubber O-rings:
O-rings are rubber rings with a circular cross-section, also known as O-rings because of their O-shaped cross-section. They first appeared in the mid-19th century, when they were used as sealing elements for steam engine cylinders. They are the most widely used type in hydraulic and pneumatic systems. They are usually called O-rings in Taiwanese and Japanese companies.
　　O-rings are annular rubber seals with a circular cross-section. They are mainly used in mechanical components under static conditions to prevent leakage of liquid and gaseous media. In some cases, O-rings can also be used as dynamic sealing elements for axial reciprocating motion and low-speed rotary motion. Different materials can be selected according to different conditions.
　　When selecting O-rings, it is generally recommended to select O-rings with a larger cross-section. Under the same gap, the volume of the O-ring squeezed into the gap should be less than its maximum allowable squeezed value.
For different types of fixed or dynamic sealing applications, O-rings provide designers with an effective and economical sealing element. O-rings are bi-directional sealing elements. The initial compression in the radial or axial direction during installation gives the O-ring its initial sealing capability. The sealing force generated by the system pressure and the initial sealing force combine to form the total sealing force, which increases with the increase of the system pressure. O-rings show outstanding performance in static sealing applications. However, O-rings are also often used in appropriate dynamic applications, but they are limited by the speed and pressure at the sealing point.

2. Advantages:
1) Compact structure, easy to install and disassemble,
2) Can be used for both static and dynamic sealing,
3) Relatively small dynamic friction resistance,
4) Using a single O-ring can seal in two directions

3. O-ring specifications and standards:
O-ring specifications and models mainly include UHS O-ring specifications, UHP O-ring specifications, UNO O-ring specifications, DHO O-ring specifications, piston rod O-ring specifications, high-temperature resistant O-rings, high-pressure resistant O-rings, corrosion-resistant O-rings, and wear-resistant O-rings.
　　O-rings have excellent sealing performance and long service life. The dynamic pressure sealing service life is 5-10 times higher than that of conventional rubber seals, and can reach tens of times in some cases. Under certain conditions, it can have the same service life as the sealing substrate.
　　O-rings have low frictional resistance, and the dynamic and static frictional forces are equal, which is 1/2-1/4 of the frictional force of a "0" shaped rubber ring, eliminating the "crawling" phenomenon under low speed and low pressure.
　　O-rings are highly wear-resistant, and the sealing surface has an automatic elastic compensation function after wear.
　　O-rings have good self-lubricating properties and can be used as oil-free lubrication seals.
　　O-rings have a simple structure and are easy to install.
　　O-ring working pressure: 0-300MPa; working speed: ≤15m/s; working temperature: -55-250 degrees.
O-rings are suitable for hydraulic oil, gas, water, mud, crude oil, emulsion, water-ethylene glycol, and acid.

4. Application range of O-rings:
O-rings are suitable for installation on various mechanical equipment, and play a sealing role in static or dynamic states under specified temperature, pressure, and different liquid and gas media. They are widely used in machine tools, ships, automobiles, aerospace equipment, metallurgical machinery, chemical machinery, engineering machinery, construction machinery, mining machinery, petroleum machinery, plastic machinery, agricultural machinery, and various instruments and meters. O-rings are mainly used for static sealing and reciprocating motion sealing. When used for rotary motion sealing, they are limited to low-speed rotary sealing devices. O-rings are generally installed in rectangular grooves on the outer or inner circle to achieve sealing.

Rubber seal compound formulation design:
〈1〉 Principles of formulation design:
Rubber formulations generally consist of raw rubber, vulcanization antioxidants, reinforcing agent systems, protective systems, reinforcing systems, and softening systems. The purpose of formulation design is to find the optimal combination of various components to obtain good comprehensive performance. The ultimate goal of formulation design is to achieve the following:
1. Meet the performance requirements of the sealing ring.
2. Good rubber processing performance.
3. On the premise of ensuring product quality, choose raw materials that are cheap, abundant, non-toxic or low-toxic, and stable in performance.
Rubber formulations can be divided into experimental formulations and practical formulations according to their uses. The former is used to study or identify the relationship between certain raw materials and the properties of vulcanized rubber and mixed rubber, and the composition is simple. Practical formulations mainly study the relationship between the properties of vulcanized rubber and the actual use performance of products and the processing performance of mixed rubber. The process of formulating practical formulations is: analysis of product use environment conditions and manufacturing processes → selection of rubber types and components of various compounding agents to form experimental formulations → performance evaluation tests → component adjustment and improvement → expanded tests to determine practical formulations.

〈2〉 Seal ring rubber compound formulation design:
Rubber sealing rings operate in a wide variety of complex environments, requiring the rubber material to possess certain special properties. In hydraulic systems, good oil resistance, temperature resistance, low compression set, and a certain tensile strength are required. As a dynamic seal, in addition to the above requirements, the rubber material should also have good wear resistance and tear resistance. Seals used in special media require that the volume and hardness changes of the rubber material in the medium are small. In short, the formulation design should comprehensively consider the specific working conditions, medium type, operating temperature, working pressure, and application status.

〈Three〉 Rubber Material Processing for Sealing Rings:
Rubber sealing rings are mainly produced using the molding method, and the vulcanization methods for molded products mainly include three types: flat molding, transfer molding, and injection molding. The flat molding method has the longest history. Transfer molding began to be used around the 1950s, while injection molding gradually entered the rubber industry from the plastics industry since the 1960s. The current development trend is to gradually develop injection molding, but due to the different applicable ranges, the three methods coexist and develop. Sealing rings, according to their characteristics, are still mainly formed by flat molding. During the molding and vulcanization process, the vulcanization temperature, time, and pressure must be strictly and correctly controlled, and the changes in parameters such as temperature during the vulcanization process must be monitored and handled accordingly; otherwise, under-vulcanization or over-vulcanization will occur. If an automatic control system is used, the entire vulcanization process will be automatically recorded and controlled to ensure that the product reaches the correct degree of vulcanization.
Vulcanization temperature is one of the basic conditions for the vulcanization reaction of rubber sealing rings, and it directly affects the vulcanization speed and product quality. A high vulcanization temperature results in a fast vulcanization speed and high production efficiency; a low vulcanization temperature results in a slow vulcanization speed. The vulcanization temperature is determined according to the formula, and the most important factor is the type of rubber and the vulcanization system used. The most suitable vulcanization temperature for natural rubber is generally 143℃-150℃, and for synthetic rubber, it is generally 150℃-180℃. The vulcanization time is usually determined through experiments based on the determined vulcanization temperature.
Pressurization during the vulcanization process of the product is to facilitate the flow of the rubber material, fill the cavity, prevent the formation of bubbles during vulcanization, and improve the density of the product. The size of the vulcanization pressure depends on the hardness of the rubber material and the size of the mold. When the rubber material has high hardness and the mold size is large, the pressure can be increased; conversely, the pressure should be appropriately reduced.