There are currently three most commonly used sealing materials for solenoid valves.
Nitrile butadiene rubber (NBR) is produced by emulsion polymerization of butadiene and acrylonitrile. NBR is mainly produced using low-temperature emulsion polymerization. It has excellent oil resistance, high abrasion resistance, good heat resistance, and strong adhesion. Its disadvantages include poor low-temperature resistance, poor ozone resistance, poor electrical properties, and slightly lower elasticity.
In addition, it also has good water resistance, airtightness, and excellent adhesion. It is widely used in the manufacture of various oil-resistant rubber products, various oil-resistant gaskets, washers, sleeves, flexible packaging, flexible tubing, printing and dyeing rollers, cable adhesive materials, etc., and has become an indispensable elastic material in the automotive, aerospace, petroleum, and photocopying industries.
Nitrile butadiene rubber has excellent oil resistance, second only to polysulfide rubber and fluororubber, and also possesses good abrasion resistance and airtightness. The disadvantages of NBR are that it is not resistant to ozone and aromatic, halogenated hydrocarbons, ketones, and ester solvents, and is not suitable as an insulating material. Main Uses: Nitrile rubber is mainly used to make oil-resistant products, such as oil-resistant pipes, belts, rubber diaphragms, and large oil bladders. It is commonly used in the manufacture of various oil-resistant molded products, such as O-rings, oil seals, cups, diaphragms, valves, and bellows. It is also used to make rubber sheets and wear-resistant parts.
EPDM (Ethylene Propylene Diene Monomer) Rubber: Ethylene propylene diene monomer (EPDM) is a terpolymer of ethylene, propylene, and a non-conjugated diene. Commercial production began in 1963. Global consumption is 800,000 tons annually. The most important characteristics of EPDM are its superior resistance to oxidation, ozone, and corrosion. As EPDM belongs to the polyolefin family, it has excellent vulcanization properties. Among all rubbers, EPDM has the lowest specific gravity. It can absorb large amounts of fillers and oils with minimal impact on its properties. Therefore, it can be used to produce low-cost rubber compounds.
Molecular Structure and Properties: Ethylene propylene diene monomer (EPDM) is a terpolymer of ethylene, propylene, and a non-conjugated diene. Dienes have a unique structure, requiring only one of their two bonds to copolymerize; the unsaturated double bond primarily serves as a crosslinking site. The other unsaturated bond does not form the polymer backbone but rather a side chain. In contrast, the main polymer chain of EPDM is fully saturated. This characteristic makes EPDM resistant to heat, light, oxygen, and especially ozone. EPDM is inherently nonpolar, resistant to polar solutions and chemicals, has low water absorption, and possesses excellent insulating properties.