1, o-ring definition
O-ring is a rubber sealing ring with circular cross section. Because their cross section is O-shaped, they are called O-rings, also known as O-rings. /kloc-began to appear in the middle of 0/9th century, when it was used as the sealing element of steam engine cylinder.
2. Scope of application of O-ring
O-ring is suitable for all kinds of mechanical equipment, which can play a sealing role in static or moving under specified temperature, pressure and different liquid and gas media. Various types of seals 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.
O-ring seal is mainly used for static seal and reciprocating seal. When used for rotary sealing, it is limited to low-speed rotary sealing device. O-ring is generally installed in the groove with rectangular section on the outer circle or the inner circle for sealing.
O-ring can still play a good sealing and damping role in oil, acid, alkali, wear and chemical corrosion.
Therefore, O-ring seal is the most widely used seal in hydraulic and pneumatic transmission systems.
3. Advantages of O-ring
Compared with other types of sealing rings, O-rings have the following advantages:
(1) is suitable for various sealing forms: static sealing and dynamic sealing.
(2) Materials suitable for various purposes, with standardized dimensions and grooves, and highly interchangeable.
(3) Suitable for all kinds of motion modes: rotary motion, axial reciprocating motion or combined motion (such as rotary reciprocating combined motion).
(4) Suitable for many different sealing media: oil, water, gas, chemical media or other mixed media.
(5) Oil, water, air, gas and various chemical media can be effectively sealed by selecting appropriate rubber materials and designing appropriate formulas. The temperature range is wide (-60℃ ~+220℃), and the pressure can reach 1500Kg/cm2 when fixed (used in conjunction with the reinforcing ring).
(6) Simple design, compact structure and convenient disassembly.
4. The cross-sectional structure of O-ring is extremely simple, with self-sealing function and reliable sealing performance.
Because the O-ring itself and the structure of the installation part are extremely simple and standardized, it is very easy to install and replace.
(1) There are many kinds of materials.
It can be selected according to different fluids: nitrile rubber (NBR), fluororubber (FKM), silicone rubber (VMQ), ethylene-propylene rubber (EPDM), neoprene (CR), butyl rubber (BU), polytetrafluoroethylene (PTFE), natural rubber (NR), etc.
(2) low cost
(3) The dynamic friction resistance is relatively small.
Second, the representation of O-rings.
1 and GB/T342. 1
Inner diameter d 1× line diameter d2.
Implement the national standard GB3452. 1.
For example: O-ring 20*2.4, II-2GB 1235-XX, where 20 represents the inner diameter of 20 mm large ring, 2.4 represents the cross-sectional diameter of 2.4 mm apron, II-2 represents the type of rubber used, GB 1235 represents the standard number, and XX represents the year when the standard was issued.
Representation of 2.GB/T 3452.438+0-2005.
For example: o-ring 7.5× 1.8-G-N,
7.5—— Inner diameter
1.8- section diameter
G series
N-level
3. The material is HG/T2579-2008.
Representation of O-rings for mechanical seals in 4.JB/T7757.2-2006.
For example: o-ring 7.5× 1.8-G-N,
7.5—— Inner diameter
1.8- section diameter
G series
N-level
Material: nitrile rubber,
Ethylene propylene rubber, etc.
III. Comparison of O-ring materials classification, advantages and disadvantages:
1, natural rubber NR
Natural rubber is a polymer of isoprene, which is made of latex collected from rubber trees. It has good wear resistance, high elasticity, breaking strength and elongation. Easy to age in air, sticky when heated, easy to swell and dissolve in mineral oil or gasoline, alkali-resistant but not strong acid-resistant. It is the raw material for manufacturing adhesive tape, rubber hose and rubber overshoes, and is suitable for manufacturing damping components and products used in hydroxyl-containing liquids such as automobile brake oil and ethanol.
2, styrene-butadiene rubber SBR
Compared with natural rubber, the polymer of butadiene and styrene has uniform quality and less impurities, but its mechanical strength is weak, so it can be blended with natural rubber.
(1) Advantages:
Low-cost non-oil resistant materials.
Good water resistance, good elasticity and hardness below 70.
It has poor compression deformation at high hardness.
Most neutral chemicals and dry and nutritious organic ketones can be used.
(2) Disadvantages:
? Strong acids, ozone, oil, grease and most hydrocarbons are not recommended.
? Widely used in tire industry, shoe industry, cloth industry and conveyor belt industry.
3. Butyl rubber
Butyl rubber is polymerized from isobutylene and a small amount of isoprene, and a small amount of unsaturated groups are reserved for sulfur addition. Because sterically hindered molecules of methyl move less than other polymers, it has less air permeability, stronger resistance to heat, sunlight and ozone, and better electrical insulation. It is resistant to polar solvents, such as alcohol, ketone, ester and so on. The general temperature range is -54~ 1 10℃.
(1) Advantages:
Impermeability to most common gases.
Good resistance to sunlight and ozone.
May come into contact with animals or vegetable oils or oxidizable chemicals.
(2) Disadvantages:
It is not recommended to use it with petroleum solvents, colloidal kerosene and aromatic hydrogen.
? Used for manufacturing rubber parts of chemical corrosion resistant and vacuum equipment.
4. Hydrogenated nitrile rubber HNBR
Hydrogenated nitrile rubber is a kind of nitrile rubber with partial double chains removed after hydrogenation. After hydrogenation, the temperature resistance and weather resistance are much higher than those of ordinary nitrile rubber, and the oil resistance is similar to that of ordinary nitrile rubber. The general temperature range is -25~ 150℃.
(1) Advantages:
Compared with butyl rubber, it has better wear resistance.
Excellent corrosion resistance, tensile resistance, tear resistance and compression deformation.
Good resistance to ozone, sunlight and other atmospheric conditions.
Generally speaking, it is suitable for washing clothes or washing dishes.
(2) Disadvantages:
It is not recommended to use in alcohol, ester or aromatic solution.
? Environmental protection refrigerant R 134a system seals are widely used in air conditioning and refrigeration industries.
Automobile engine system seal.
5. Ethylene propylene rubber
The main chain of ethylene-propylene rubber is not double-stranded, so it has excellent heat resistance, aging resistance, ozone resistance and stability, but sulfur cannot be added. In order to solve this problem, EPDM can be obtained by introducing a small amount of the third component with double chains into the main chain of EP and adding sulfur. The general temperature range is -50~ 150℃. Excellent resistance to polar solvents, such as alcohol, ketone, ethylene glycol and phospholipid hydraulic oil.
(1) Advantages:
It has good weather resistance and ozone resistance.
Excellent water resistance and chemical resistance.
Alcohol and ketones can be use.
High temperature steam resistance, good air tightness.
(2) Disadvantages:
Not recommended for food or contact with aromatic hydrogen.
Seals in high temperature water vapor environment.
Sanitary ware seals or parts.
Rubber parts in braking system.
Seals in radiator (automobile water tank).
6. NBR of NBR
(NBR) is polymerized from acrylonitrile and butadiene. The content of acrylonitrile ranges from18% to 50%. The higher the acrylonitrile content, the better the hydrocarbon-resistant fuel oil performance of petrochemical products, but the low-temperature performance is poor. The general temperature range is -25~ 100℃. Butadiene rubber is one of the most commonly used rubbers for oil seals and O-rings.
(1) Advantages:
It has good oil resistance, water resistance, solvent resistance and high pressure oil resistance.
Good compression deformation, wear resistance and elongation.
(2) Disadvantages:
Not suitable for polar solvents, such as ketone, ozone, nitrohydrocarbon, MEK and chloroform.
Used for manufacturing fuel tanks, lubricating oil tanks and rubber parts, especially seals, and used for fluid media such as petroleum hydraulic oil, gasoline, water, silicone grease, silicone oil, diester lubricating oil and ethylene glycol hydraulic oil. It can be said that it is the most widely used rubber seal with the lowest cost at present.
7, chloroprene rubber CR
(chloroprene rubber, polychloroprene) is polymerized from chloroprene monomer. Vulcanized rubber has good elasticity and wear resistance, is not afraid of direct sunlight, especially has good atmospheric aging resistance, strong twisting resistance, resistance to refrigerants such as dichlorodifluoromethane and ammonia, resistance to dilute acid and silicone ester lubricating oil, and resistance to phosphate ester hydraulic oil. It is easy to crystallize and harden at low temperature and has poor storage stability. It has great expansion in mineral oil with low aniline point. Generally speaking, the temperature range is -50~ 150℃
(1) Advantages:
Good elasticity and good compression deformation.
This formula does not contain sulfur, so it is easy to make.
It has anti-animal and vegetable oil properties.
Physical properties will not be affected by neutral chemicals, esters, oils, various oils and solvents.
It has the characteristics of fire prevention.
(2) Disadvantages:
Strong acids, nitro-hydrocarbons, esters, chloroform and ketones are not recommended.
R 12 refrigerant-resistant seal.
Rubber parts or seals on household appliances.
Suitable for making all kinds of parts that are in direct contact with the atmosphere, sunlight and ozone.
Suitable for all kinds of fire-resistant and chemical-resistant rubber products.
8. CSM of chlorosulfonated polyethylene adhesive
(Hypalon, polyethylene) chlorosulfonated polyethylene is a kind of synthetic rubber patented by DuPont. Good heat resistance, weather resistance and ozone resistance; Acid resistance is also good, and it is often used in places where antioxidant drugs (nitric acid and sulfuric acid) are used, and the general temperature range is -45~ 120℃.
(1) Advantages:
Good ozone resistance, oxidation resistance and flame retardancy.
Physical properties are similar to chloroprene rubber, which has better acid resistance.
Excellent wear resistance.
It has the same low friction surface as butyl rubber.
Oil resistance and solvent resistance are between NBR and chloroprene rubber.
It is recommended to use water to prevent leakage.
(2) Disadvantages:
Exposure to concentrated oxidizing acids, nitrohydrocarbons, esters, ketones and aromatic hydrogen is not recommended.
9. Silicone rubber si
(Silicone rubber) The main chain of silica gel is composed of silicon (-si-o-si). Excellent heat resistance, cold resistance, ozone resistance and atmospheric aging resistance. It has good electrical insulation performance. The tensile strength is worse than that of ordinary rubber, and there is no oil resistance.
(1) Advantages:
The tensile strength can reach 1500PSI and the tear strength can reach 88LBS.
Good elasticity and good compression deformation.
Good resistance to neutral solvents.
Excellent heat resistance.
It has excellent cold resistance.
Excellent ozone and oxidation corrosion resistance.
Excellent electrical insulation performance
Good heat insulation and heat dissipation performance.
(2) Disadvantages:
? It is not recommended to use in most concentrated solvents, oils, concentrated acids and diluted sodium hydroxide.
? Seals or rubber parts used in household appliances industry, such as rubber parts in electric cookers, irons and microwave ovens.
? Seals or rubber parts in electronic industry, such as mobile phone keys, shock absorbers in DVD, and seals in cable joints.
? Seals on various articles in contact with human body, such as kettles and drinking fountains.
10, silicone fluororubber FLS
Fluorescent silicone rubber is fluorinated silicone rubber, and its general properties have the advantages of both fluororubber and silicone rubber. Its oil resistance, solvent resistance, fuel oil resistance and high and low temperature resistance are all good, and the general use temperature is -50~200℃.
(1) Advantages:
? Suitable for special purposes, such as corrosion resistance of oxygen-containing chemicals, aromatic hydrogen-containing solvents and chlorine-containing solvents.
(2) Disadvantages:
? It is not recommended to touch the solution of brake oil, ketone and bladder. ?
? On the space machine.
1 1, fluororubber FPM
(Fluorocarbon rubber) There are many types of rubber containing fluorine in the molecule according to fluorine content (that is, monomer structure). At present, the widely used hexafluororubber was first listed by DuPont under the trade name "Viton". High temperature resistance is better than silicone rubber, and it has excellent chemical resistance, resistance to most oils and solvents (except ketones and esters), weather resistance and ozone resistance; Cold resistance is poor, and the general temperature range is -20~250℃. The special formula can resist the low temperature of -40℃.
(1) Advantages:
The heat-resistant temperature is as high as 250℃
It is resistant to most oils and solvents, especially all acids, aliphatic hydrocarbons, aromatic hydrocarbons and animal and vegetable oils.
(2) Disadvantages:
Not recommended for ketones, low molecular weight esters and mixtures containing nitrates.
Automobile, locomotive, diesel engine and fuel system.
Seals for chemical plants.
12, perfluororubber FFPM
(perfluoroelastomer)
(1) Advantages:
Optimum heat resistance
Excellent chemical resistance
Low outgassing characteristics
Excellent plasma resistance.
(2) Disadvantages:
Low temperature resistance is poor.
The price of raw materials is higher.
It is difficult to produce.
Perfluorinated products are widely used in semiconductor industry and information-related industries, including PVC, CVD and etching processes in thin film technology and various high vacuum sealing processes.
13, acrylic rubber ACM
Polyacrylate rubber is an elastomer polymerized with alkyl acrylate as the main component. It has good petrochemical oil resistance, high temperature resistance and weather resistance, but its mechanical strength, compression deformation rate and water resistance are weak, which is slightly worse than ordinary oil-resistant rubber. The general temperature range is -25~ 170℃.
(1) Advantages:
Suitable for automobile transmission oil.
It has good oxidation resistance and weather resistance.
It has the function of resisting bending deformation.
Excellent oil-resistant product performance
Suitable for automobile transmission system and power steering wheel.
(2) Disadvantages:
Not suitable for hot water.
Not applicable to brake oil.
Does not have the function of low temperature resistance.
Not suitable for phosphate ester?
Automobile transmission system and power system seal.
14, polyurethane rubber PU
Polyurethane rubber has quite good mechanical properties, and its high hardness, high elasticity and wear resistance are incomparable with other rubbers. Aging resistance, ozone resistance and oil resistance are also quite good. The general temperature range is -45~90℃.
(1) Advantages:
Wear resistance and high pressure resistance
(2) Disadvantages:
Not resistant to high temperature?
Industrial high-pressure wear-resistant seals, such as hydraulic cylinder seals.
High voltage and high charge system.
Four. English abbreviation and English alias of chemical description of material name
Material name chemical description English abbreviation English alias
nitrile rubber
Hydrogenated nitrile rubber
EPDM
chloroprene rubber
Silicone silicone rubber WMQPVMQ
Fluorosiloxane fluorosilicone rubber
acrylic rubber
Ethylene vinyl acrylate-acrylic rubber
butadiene-styrene rubber
Polyurethane polyester/polyether polyurethane AU/EuAU/EU
Natural rubber NRNR natural rubber
butadiene-styrene rubber
The verb (verb's abbreviation) uses an O-ring thermometer.
Basic properties nbrhnbrepdmfkmcracmaemsbrau/euvmqfvmqnr
High temperature (standard,? f)2 123003003902503503002 122 12390400220
High temperature (special,? F)250 - 480 -
Low temperature (standard,? 22-22-605-400-40-40-40-65-75-60
Low temperature (special,? 60-40 - 30 -
Comparison of material characteristics of intransitive verbs
Material selection of 1 and o-ring
Materials used as O-rings include nitrile rubber, carboxylic acid nitrile, fluororubber, ethylene propylene rubber, hydrogenated nitrile rubber, silicone rubber, chloroprene rubber, fluorosilicone rubber, polyurethane, chlorohydrin rubber, styrene-butadiene rubber, butyl rubber, natural rubber, ethylene/vinyl propionate rubber, polyacrylate rubber, perfluororubber, etc.
The performance index of the same kind of rubber also varies greatly due to different formulations. Therefore, it is not accurate to simply fill in NBR or NBR -40 in the material column. The Ministry of Materials and Chemical Industry has special standards for O-rings, such as HG/T 2579, HG/T 202 1, HG/T 2333, HG/T 3089, HB 5290, etc. HG/T 2579 specifically removes the specific categories of materials and only gives some performance indicators of materials.
2. The choice of O-ring hardness is more important. For example, the sealing ring with hardness of 70 (Shore) of pump turbine in a power station often peels off or even cuts off horizontally, and then the sealing ring with hardness of 85 ~ 90 (Shore) is adopted, and the effect is ideal.
3. Low hardness, convenient installation, but easy to peel, installation damage, extrusion and even explosion. The hardness is too high and the installation is inconvenient.
4. Under normal circumstances, the hardness of O-ring is 40 ~ 90 IRHD, but in use, 70IRHD is more suitable, except for silicone rubber, and 60 IRHD is generally used.