Knowledge of sealing materials for solenoid valves

At present, there are three most commonly used sealing materials for solenoid valves. Here is an introduction:

I. NBR (NR butadiene rubber)

Obtained from emulsion polymerization of butadiene and acrylonitrile, acrylonitrile butadiene rubber is mainly produced by low temperature emulsion polymerization. It has excellent oil resistance, high wear resistance, good heat resistance and strong adhesion. Its disadvantages are low temperature resistance, poor ozone resistance, poor electrical performance and low elasticity.

In addition, it also has good water resistance, air tightness and excellent bonding performance. It is widely used in the manufacture of various oil-resistant rubber products, various oil-resistant washers, gaskets, casings, flexible packaging, flexible rubber tubes, printing and dyeing rubber rollers, cable rubber materials, etc. it has become an essential elastic material in the automotive, aviation, petroleum, copying and other industries.

NBR has excellent oil resistance, which is second only to polysulfide rubber and fluororubber, and has wear resistance and air tightness. The disadvantage of NBR is that it is not resistant to ozone and aromatic, halogenated hydrocarbon, ketone and ester solvents, so it is not suitable for insulating materials.

Main use: NBR is mainly used for making oil resistant products, such as oil pipe, tape, rubber diaphragm and large oil bag. It is commonly used for making various oil resistant molded products, such as O-ring, oil seal, leather bowl, diaphragm, valve, bellows, etc., and also for making rubber plate and wear-resistant parts.

II. EPDM ethylene propylene diene monomer

EPDM is a terpolymer of ethylene, propylene and non conjugated diene. It began commercial production in 1963. The annual consumption of the world is 800000 tons. The most important characteristic of EPDM is its superior ability to resist oxidation, ozone and erosion. Because EPDM belongs to polyolefin family, it has excellent vulcanization properties. EPDM has the lowest specific gravity of all rubbers. It can absorb a large number of fillers and oil, but has little effect on its properties. Therefore, the rubber compound with low cost can be made.

Molecular structure and properties

Structure: EPDM is a terpolymer of ethylene, propylene and non conjugated diene. Diene has a special structure, only one of the two bonds can be copolymerized, the unsaturated double bond is mainly used as the cross chain. The other unsaturated one will not be the main chain of polymer, but the side chain. The main polymer chain of EPDM is completely saturated. This property makes EPDM resistant to heat, light, oxygen, especially ozone. EPDM is essentially nonpolar, resistant to polar solutions and chemicals, with low water absorption and good insulation properties.

Features: 1. Electrical properties; 2. Elasticity; 3. Adhesion; 4. Low density and high filling; 5. Hot water resistance; 6. Water vapor resistance; 7. Aging resistance; 8. Corrosion resistance.

III. Viton fluororubber (FKM)

There are various types of rubber containing fluorine according to fluorine content or monomer structure. Currently, the widely used fluororubber of hexafluoride series was first listed by DuPont company under the trade name of "Viton" High temperature resistance is better than silicone rubber Chemical resistance, resistance to most oils and solvents (except ketones and esters), good weather resistance and ozone resistance, but poor cold resistance; generally widely used in steam turbine cars, B and other products, chemical plant seals, use temperature range - 20 ℃ ~ 260 ℃, low temperature resistant type can be used to - 40 ℃, but the price is high.