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Types and uses of seal materials with good heat and cold resistance

Release time:

2021-01-12

Imported sealing material should meet the requirements of sealing function. Due to the different sealing media and different working conditions of the equipment, the sealing material is required to have different adaptability.

Types and uses of seal materials with good heat and cold resistance

1) The material has good compactness and is not easy to leak the medium;

2) Appropriate mechanical hardness and strength;

3) Good compression and resilience, and small permanent deformation;

4) It does not soften or decompose under high temperature, and does not harden or brittle under low temperature;

5) Good corrosion resistance, long-term work in acid, oil, alkali and other media, small changes in volume and hardness, and will not adhere to metal surfaces;

6) Small friction coefficient and good wear resistance;

7) It has the flexibility to combine with the sealing surface;

8) Good aging resistance and durability;

9) Convenient processing and manufacturing, low price and easy to obtain materials.

10) Imported sealing ring is the most commonly used sealing material.

In addition to rubber, graphite, PTFE and various sealants are also suitable for sealing materials.

General-purpose rubber seal products are more and more widely used in defense, chemical, coal, petroleum, metallurgy, transportation and machinery manufacturing industries, and have become the basis and accessories in various industries.

Commonly used materials for rubber sealing products are as follows:

1. Nitrile rubber:

Nitrile rubber has excellent properties such as fuel oil and aromatic solvents, but it is not resistant to media such as ketones, esters and hydrogen chloride, so oil-resistant sealing products and nitrile rubber are mainly used.

2. Neoprene:

Neoprene rubber has good oil and solvent resistance. It has good resistance to gear oil and variable pressure oil, but it is not resistant to aromatic oils. Neoprene rubber also has excellent resistance to weathering and ozone aging. The cross-linking rupture temperature of neoprene is above 200℃, and neoprene is usually used to make door and window seals. Neoprene rubber also has good corrosion resistance to inorganic acids. In addition, because neoprene rubber has good flexibility and gas impermeability, it can be made into diaphragm and vacuum sealing products.

3. Natural rubber:

Compared with most synthetic rubbers, natural rubber has good comprehensive mechanical properties, cold resistance, higher resilience and abrasion resistance. Natural rubber is not resistant to mineral oil, but it is more stable in vegetable oils and alcohols. In the hydraulic brake system of the brake fluid composed of n-butanol and refined castor oil mixed liquid, the rubber bowl is used as the seal, and the rubber ring is made of natural rubber. Generally, the sealant is also made of natural rubber.

4. Fluorine rubber:

Fluorine rubber has outstanding heat resistance (200~250°C) and oil resistance. It can be used to manufacture cylinder seals, rubber bowls and rotating lip seals, which can significantly increase the use time.

5. Silicone rubber:

Silicone rubber has outstanding high and low temperature resistance, ozone resistance and weathering resistance. It can maintain its unique flexibility and ozone resistance and weather resistance within the working temperature range of -70~260℃. It is suitable for making heat mechanism Required gaskets, such as strong light source lampshade gaskets, valve gaskets, etc. Since silicone rubber is not resistant to oil, has low mechanical strength, and is expensive, it is not suitable to make oil-resistant sealing products.

6. EPDM rubber:

The main chain of EPDM rubber is a fully saturated linear structure without double bonds, and its side chain has diolefins, so that it can be vulcanized with sulfur. EPDM rubber has excellent aging resistance, ozone resistance, weather resistance, heat resistance (can be used for a long time in an environment of 120 ℃), chemical resistance (such as alcohol, acid, strong alkali, oxidant), but not Resistant to aliphatic and aromatic solvents. EPDM rubber has the lowest density in rubber and has high filling characteristics, but it lacks self-adhesiveness and mutual adhesion. In addition, EPDM rubber has outstanding steam resistance and can be used to make sealing products such as steam resistant diaphragms. EPDM rubber has been widely used in washing machines, TV accessories and door and window sealing products, or the production of multiple composite profiles.

7. Polyurethane rubber:

Polyurethane rubber has excellent abrasion resistance and good gas impermeability, and its use temperature range is generally -20~80℃. In addition, it also has medium oil resistance, oxygen resistance and ozone aging resistance, but it is not resistant to acid, alkali, water, steam and ketones. It is suitable for manufacturing various rubber sealing products, such as oil seals, imported sealing rings and diaphragms.

8. Chloroether rubber:

Chloroether rubber has the advantages of nitrile rubber and acrylate rubber. Its oil resistance, heat resistance, ozone resistance, flame resistance, alkali resistance, alkali resistance, water resistance and organic solvent resistance are all very good, and it has good process performance. The cold resistance is poor. When the operating temperature is not too low, chloroether rubber is still a good material for sealing products such as oil seals, various sealing rings, gaskets, diaphragms and dust covers.

9. Acrylic rubber:

Acrylic rubber has heat-resistant oils (mineral oil, lubricating oil and fuel oil), especially oil-resistant stability at high temperatures, generally up to 175°C, and can withstand temperatures of 200°C for intermittent use or short-term use. His disadvantage is poor cold resistance. Therefore, it is suitable to make oil seals resistant to high temperature oil in non-cold areas, but it is not suitable for sealing products subjected to tensile or compressive stress at high temperatures.

10. Nitrile rubber:

Oil resistance, heat resistance, good wear resistance, widely used in the production of sealing products, but not for phosphate ester series hydraulic and gear oils containing polar additives. -40~120℃, used for making O-rings and sealing oil, suitable for general hydraulic and pneumatic systems.

11. Hydrogenated nitrile rubber:

High strength, oil resistance, wear resistance, heat resistance and aging resistance. -40~150℃, used for high-temperature, high-speed reciprocating and rotary sealing.

12. Rubber and plastic:

The material has large elastic modulus and high strength, and other properties are the same as above. -30~80℃, used to make O-rings, Y-rings, dust-proof rings, etc., used in construction machinery and high-pressure hydraulic system seals.

13. Viton:

Heat resistance, acid and alkali resistance and other chemicals, oil resistance (including phosphate ester series hydraulic oil), suitable for all lubricating oil, gasoline, hydraulic oil, synthetic oil. -20~200℃, suitable for sealing of high temperature resistance, chemical medicine, flame-resistant hydraulic oil, and widely used in metallurgy, electric power and other industries.

14. Polyurethane:

Excellent wear resistance, high strength, good aging resistance, -20~80℃. Suitable for high-pressure and high-speed system sealing in engineering machinery and metallurgical equipment.

15. Silicone rubber:

It has good heat and cold resistance, small compression set, but low mechanical strength, -60~23℃. Suitable for high-speed rotating seals and food machinery seals at high and low temperatures.

16. Polyacrylate:

The heat resistance is better than NBR, and it can work in various lubricating oils, hydraulic oils, and petroleum hydraulic oils containing polar additives, with poor water resistance. -20~150℃, can be used for various car oil seals and various gearboxes and gearboxes, and can withstand medium and high temperature.

17. Polytetrafluoroethylene:

Good chemical stability, good heat and cold resistance, resistance to various media such as water, oil, steam, and drugs. High mechanical strength, high temperature resistance, abrasion resistance, extremely low friction coefficient, and good self-lubrication. -55~260℃, making wear-resistant rings, guide rings, and retaining rings are commonly used densely on machinery

Seal materials are widely used in metallurgy, petrochemical, engineering machinery, and light industry machinery.

18. Nylon:

Good oil resistance, heat resistance, abrasion resistance, high compressive strength, good impact resistance, but poor dimensional stability. -40~120℃, used to make guide ring, support ring, pressure ring and retaining ring.

19. Polyoxymethylene:

Oil resistance, heat resistance, good wear resistance, high compressive strength, good impact resistance, good self-lubricating performance, good dimensional stability, but poor flexibility. -40~140℃. Used to make guide rings and retaining rings.