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

Release time:

2021-09-15

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

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

The imported seal material should meet the needs of the sealing function. Due to the different sealing medium and the different working conditions of the equipment, different adaptability of the sealing material is required. The requirements for sealing materials are generally:

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

2) have appropriate mechanical hardness and strength;

3) Good compression and resilience, small permanent deformation;

4) No softening or decomposition at high temperature, no hardening or brittle cracking at low temperature;

5) Good corrosion resistance, can work for a long time in acid, oil, alkali and other media, the change in volume and hardness is small, and it will not adhere to the metal surface;

6) Small friction coefficient and good wear resistance;

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

8) Good aging resistance and durable;

9) It is easy to manufacture, cheap and easy to obtain.

10) The imported sealing ring is the most commonly used sealing material.

In addition to rubber, graphite, PTFE and various sealants are suitable for sealing materials. General rubber seal products are more and more widely used in national defense, chemical industry, coal, petroleum, metallurgy, transportation and machinery manufacturing industries, and have become the basis and accessories in various industries.

Common 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 ketones, esters and hydrogen chloride and other media, so oil-resistant sealing products and nitrile rubber are mainly used.

2. Neoprene:

Neoprene has good oil and solvent resistance. It has better resistance to gear oils and transformer oils, but not to aromatic oils. Neoprene also has excellent resistance to weathering and ozone aging. The cross-linking breaking temperature of neoprene is above 200°C, and it is usually used to make door and window seals. Neoprene also has good corrosion resistance to inorganic acids. In addition, because neoprene also has good flexibility and airtightness, it can be made into diaphragms and vacuum sealing products.

3. Natural rubber:

Compared with most synthetic rubbers, natural rubber has good comprehensive mechanical properties, cold resistance, high resilience and wear resistance. Natural rubber is not resistant to mineral oils, but is relatively 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 and rubber ring are all made of natural rubber, and the general sealant is also commonly made of natural rubber.

4. Fluorine rubber:

Fluorine rubber has outstanding heat resistance (200~250℃), oil resistance, can be used to manufacture cylinder seals, rubber bowls and rotating lip seals, which can significantly improve the service time.

5. Silicone rubber:

Silicone rubber has outstanding high and low temperature resistance, ozone resistance and weather resistance. It can maintain its unique use elasticity, ozone resistance and weather resistance in the working temperature range of -70~260℃. Sealing gaskets required, such as strong light source lampshade gaskets, valve gaskets, etc. Because silicone rubber is not oil-resistant, 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 straight-chain structure without double bonds, and there are dienes on its side chains, 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 120 ℃ environment), 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 properties, but lacks self-adhesion 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, accessories in TV sets and door and window sealing products, or the production of rubber strips for various composite profiles.

7. Polyurethane rubber:

Polyurethane rubber has excellent wear resistance and good airtightness, and the operating temperature range is generally -20~80℃. In addition, it also has moderate oil resistance, oxygen resistance and ozone aging resistance, but not acid and alkali, water, steam and ketones. It is suitable for the manufacture of various rubber sealing products, such as oil seals, inlet sealing rings and diaphragms.

8. Chloroether rubber:

Chloroether rubber has the advantages of nitrile rubber and acrylate rubber. It has good oil resistance, heat resistance, ozone resistance, flame resistance, alkali resistance, alkali resistance, water resistance and organic solvent resistance, and has good process performance. Cold resistance is poor. Under the condition that the use temperature is not too low, chloroether rubber is still a good material for making oil seals, various sealing rings, gaskets, diaphragms and dust covers and other sealing products.

9. Acrylate rubber:

Acrylate rubber has heat-resistant oil (mineral oil, lubricating oil and fuel oil), especially oil-resistant stability at high temperature, generally up to 175 °C, and can withstand temperature of 200 °C for intermittent use or short-term use. Its disadvantage is poor cold tolerance. Therefore, it is suitable for making oil seals resistant to high temperature oil in non-cold areas, but 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 seal products, but not for phosphate ester series hydraulic and gear oil containing polar additives. -40~120℃, used to make O-rings, seal oil, suitable for general hydraulic and pneumatic systems.

11. Hydrogenated nitrile rubber:

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

12. Rubber and plastic:

The material has a 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 seals of construction machinery and high-pressure hydraulic systems.

13. Fluorine rubber:

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 resistant, chemical and flame resistant hydraulic oil, widely used in metallurgy, electric power and other industries.

14. Polyurethane:

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

15. Silicone rubber:

Good heat and cold resistance, small compression set, but low mechanical strength, -60~23℃. It is suitable for high-speed rotary seals at high and low temperatures and seals for food machinery.

16. Polyacrylate:

The heat resistance is better than that of NBR, and it can work in various lubricating oils, hydraulic oils and petroleum-based hydraulic oils containing polar additives, but has 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 resistance, good cold resistance, water resistance, oil, steam, medicine and other media. High mechanical strength, high temperature resistance, wear resistance, extremely low friction coefficient, and good self-lubrication. -55~260℃, the production of wear-resistant rings, guide rings and retaining rings are commonly used in machinery.
Sealing material, widely used in metallurgy, petrochemical, construction machinery, light industrial machinery.

18. Nylon:

Oil resistance, heat resistance, good wear 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.