The properties of rubber mainly depend on the type of raw rubber used and the different formulations of rubber materials.
Types of rubber
1.1 Natural Rubber (NR)
Natural rubber (NR) is an isoprene polymer. It has excellent resilience, tensile strength, elongation, wear resistance, tear and compression permanent deformation properties are better than most synthetic rubber. Suitable for making tires, shock absorbing parts, cushioning parts and sealing parts. Oil resistance, weather resistance, ozone, oxygen performance is poor. Operating temperature range -60 ~ 100℃.
1.2 Styrene butadiene Rubber (SBR)
Styrene butadiene rubber (SBR) is a copolymer of butadiene and styrene. Butadiene-10 containing 10% styrene has good cold property, Butadiene-30 containing 30% styrene has good wear resistance. Suitable for making tires and sealing parts, the products have poor oil resistance and aging resistance. The operating temperature range is -60 ~ 120℃.
1.3 Butadiene rubber (BR)
Butadiene rubber (BR) is a butadiene polymer. The commonly used malebutadiene rubber has good cold resistance, wear resistance and resilience. Suitable for making tires, sealing parts, shock absorbing parts, tape and hose and other products. Products are not resistant to oil and aging. Operating temperature range -70~100℃.
1.4 Neoprene rubber (CR)
Chloroprene rubber (CR) is a chloroprene polymer, weather resistant, ozone aging resistance, self-extinguishing, oil resistance second only to nitrile rubber, tensile strength, elongation, resilience, and metal and fabric bonding is very good. Suitable for the production of sealing rings and sealing profiles, hose, coating, wire insulation layer, tape and preparation of adhesives. Products are not resistant to synthetic double ester lubricating oil and phosphate ester hydraulic oil. Operating temperature range -35 ~ 130℃.
1.5 Nitrile butadiene Rubber (NBR)
Nitrile butadiene rubber (NBR) is a copolymer of butadiene acrylonitrile. Generally containing acrylonitrile 18%, 26% or 40%, the higher the content, the better the oil resistance, heat resistance, wear resistance, but the cold resistance is the opposite. Nitrile rubber containing carboxyl group has better wear resistance, high temperature resistance and oil resistance than nitrile rubber. Nitrile rubber is suitable for making all kinds of oil-resistant sealing parts, diaphragms, hose and soft fuel tanks. Products are not resistant to weather, ozone aging, phosphate ester hydraulic oil. Operating temperature range -55 ~ 130℃.
1.6 Ethylene propylene rubber (EPM, EPDM)
Ethylene propylene rubber is a binary copolymer (EPM) of ethylene and propylene or a ternary copolymer (EPDM) of ethylene, propylene and diene olefin. Weather resistance, ozone aging resistance, steam resistance, phosphate ester hydraulic oil, acid, alkali and rocket fuel and oxidant, electrical insulation performance is excellent. Suitable for the production of phosphate ester hydraulic oil system sealing parts, hose and aircraft, automobile doors and Windows sealing profiles, tape and wire insulation layer. Products are not resistant to petroleum-based oils. Operating temperature range -60 ~ 150℃.
1.7 Butyl Rubber (IIR)
Butyl rubber (IIR) is a copolymer of isobutylene and isoprene. Weather resistance, ozone aging, resistance to phosphate ester hydraulic oil, acid, alkali, rocket fuel and oxidant, with excellent dielectric properties and insulation properties, minimal permeability. Suitable for the production of tire inner tube, door and window seal, sealing parts of phosphate ester hydraulic oil system, hose, wire insulation layer, tape and shock absorber. Products are not resistant to petroleum-based oils. Operating temperature range -60 ~ 150℃.
1.8 Chlorosulfonated polyethylene rubber (CSM)
Chloro-sulfonated polyethylene rubber (CSM) is resistant to weather and ozone aging, oil resistance increases with the increase of its chlorine content, acid and alkali resistance, suitable for the production of adhesive cloth, car air filter coupling sleeve, radiator drain pipe, sealing gasket, cable sleeve, anti-corrosion coating and soft oil tank outer wall. Operating temperature range -50 ~ 150℃.
1.9 Polyurethane Rubber
It is a polyurethane. There are usually two types of polyester (AU) and polyether (EU). Excellent elongation strength, tear strength and wear resistance, excellent resistance to oil, ozone, and atomic radiation. Suitable for the production of various shapes of sealing energy absorption device, punching template, vibration damping device, mechanical support gasket, flexible connection, anti-wear coating, friction power transmission device, rubber roller and so on. Operating temperature range -60 ~ 80℃. It should not be in contact with ester, ketone, phosphate ester hydraulic oil, concentrated acid, alkali, steam, etc.
1.10 Polysulfide Rubber (T)
Polythioalkane polymer, there are solid polysulfide rubber and liquid polysulfide rubber two kinds. Good oil resistance, weather aging resistance, small air permeability, electrical insulation is also good. Solid adhesives are commonly used with butadiene rubber to make sealing parts, hoses and diaphragms for fuel systems. The operating temperature range is -50 ~ 100℃, and it can reach 130℃ for a short time. Liquid adhesives are commonly used to prepare sealants.
1.11 Chlorohydrin rubber
It is an epichloropropane polymer (CO), or a binary copolymer (ECO) of epichlorohydrin and ethylene oxide, or a terpolymer with a third monomer (propylene oxide) added. It has oil resistance and ozone resistance, better heat resistance than glue, and less air permeability. Suitable for making sealing gaskets and diaphragms.
1.12 Acrylic Rubber (ACM)
Acrylic rubber (ACM) is a new type of special rubber developed in the world, with excellent heat resistance, oil resistance, cold resistance, ozone resistance and other properties. According to the needs, it can be used with fluorine rubber, butadiene rubber, chlorosulfonated polyethylene, EPDM rubber, etc., so as to obtain high temperature resistance and oil resistance. It is widely used in high temperature oil sealing materials for automobiles and military equipment, adhesive for container pipeline lining and building sealant, outer sheath of special wire and cable for sound insulation and shock absorption products.
1.13 Silicone rubber
It is polysiloxane. There are usually dimethyl silicone rubber (MQ), methyl vinyl silicone rubber (MVQ), methyl phenyl silicone rubber (MPQ), methyl phenyl vinyl silicone rubber (MPVQ) and so on. Silicone rubber has excellent heat resistance, cold resistance, aging resistance, insulation resistance, dielectric properties, good thermal conductivity, but the strength and tear resistance is poor, oil resistance, the price is more expensive. Generally suitable for the production of sealing rings, sealing profiles, oxygen bellows, diaphragm, shock absorbers, insulating materials, thermal insulation sponge board. Operating temperature range -70 ~ 280℃.
1.14 Fluorine Rubber (FPM)
Commonly used are fluorine rubber - 26, fluorine rubber - 246, the former is the copolymer of vinylidene fluoride and hexafluoropropylene, the latter is the copolymer of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. Fluorine rubber has outstanding heat resistance, oil resistance, acid resistance, alkali resistance, aging performance and electrical insulation performance, flame resistance, small permeability. But low temperature performance is poor. Generally used temperature range -40 ~ 250℃, up to 300℃ for a short time. Suitable for the production of various requirements of heat and oil resistant sealing parts, hose, tape and fuel tank, but the price is more expensive.
1.15 Fluorosilicone Rubber (MFQ)
It is a polysiloxane containing fluoroalkyl. Oil resistance, chemical resistance, heat resistance, cold resistance, aging resistance is excellent, but the strength and tear resistance is low, expensive. Suitable for the production of fuel oil, double ester lubricating oil, hydraulic oil system seal ring, diaphragm. Operating temperature range -65 ~ 250℃.
The main properties of vulcanized rubber
2.1 Tensile properties
It is the first property that should be considered for all adhesives, including tensile strength, constant elongation, elongation at break and permanent deformation at break, as well as stress-strain curves. Tensile strength is the maximum tensile stress at which a specimen is stretched to fracture. Constant elongation stress (constant elongation modulus) is the stress (modulus) achieved at specified elongation. Elongation is the deformation of the specimen caused by tensile stress, expressed as a percentage of the ratio of the increment of elongation to the original length. Elongation at break is the elongation of the specimen at break. The permanent deformation at tear is the residual deformation of the standard distance after tensile fracture.
2.2 Hardness
Indicates the ability of rubber to resist external pressure, and is also the basic property of all rubber compounds. The hardness of rubber is related to some other properties to some extent. For example, the higher the hardness of the rubber, relatively speaking, the greater the strength, the smaller the elongation, the better the wear resistance, and the poor low temperature resistance. High hardness rubber can resist extrusion damage under high pressure. Therefore, the appropriate hardness should be selected according to the working characteristics of the parts. At present, the hardness of rubber is generally measured by Shore A(HS A) hardness tester in China, which is close to the international rubber hardness value.
2.3 Compression Performance
Compression properties Rubber seals are usually in a compressed state. Due to the viscoelasticity of rubber, the compressive stress will decrease with time after the rubber is compressed, which is manifested as compressive stress relaxation. After the pressure is removed, the original shape cannot be restored, which is manifested as compression permanent deformation. In high temperature oil medium, these phenomena are more significant. They will affect the sealing performance of the seal and are one of the important properties of the sealant used in the seal.
2.4 Low temperature performance
Low temperature performance The following three methods are usually used to express the low temperature resistance of rubber. 1) The most commonly used is the brittleness temperature, which refers to the highest temperature at which the sample breaks when subjected to a certain impact force at low temperature, which can be used to compare the low temperature performance of different rubber materials. However, because the working state of rubber is different from the test conditions, the brittle temperature of rubber does not mean the lowest working temperature of rubber parts, especially in the oil medium. 2) Low temperature retraction temperature is to stretch the test piece to a certain length at room temperature, then fixed, quickly cooled to below the freezing temperature, after reaching the temperature balance, release the test piece, and warm up at a certain speed, record the temperature of the test piece retraction of 10%, 30%, 50% and 70%, respectively, TR10, TR30, TR50 and TR70. In the material standard, TR10 is generally used as the standard, which is close to the brittleness temperature of rubber. 3) Cold resistance coefficient, generally the sample is compressed at room temperature to a certain amount of deformation, and then frozen at the specified low temperature, and then the load is removed to restore it at low temperature, the ratio of recovery and compression is called the compression cold resistance coefficient. The greater the coefficient, the better the cold resistance of the rubber.
2.5 Oil resistance
Rubber in the oil medium (fuel oil, lubricating oil, hydraulic oil, etc.), especially at higher temperatures, will lead to expansion, softening and reduce strength, hardness, while the plasticizer or soluble substance in the rubber may be leach by the oil, resulting in weight reduction, volume reduction, causing leakage. Therefore, the oil resistance of rubber is an important property of working rubber in the oil medium. Generally, after soaking in oil at a certain temperature for a number of time, the weight changes, volume changes, and changes in strength, elongation and hardness are measured. Sometimes it can also be expressed by the oil resistance coefficient, that is, the ratio of the strength or elongation after soaking in the medium to the original strength or elongation.
2.6 Aging resistance
Rubber by oxygen (air), ozone, heat, light, moisture and mechanical stress and other factors will cause the performance of the deterioration, called the aging of rubber. The aging resistance of rubber can be determined by natural aging and artificial accelerated aging tests (thermal aging, wet heat aging, ozone aging, etc.). The aging resistance can be expressed by the change of the strength, elongation or hardness of the sample after aging, or the aging coefficient, that is, the ratio of the product of the tensile strength, elongation at break or tensile strength and elongation at break of the sample after aging to the original value. Accordingly, it is called the aging coefficient calculated by tensile strength (referred to as the aging coefficient by strength), the aging coefficient calculated by elongation at break (referred to as the aging coefficient by elongation) or the aging coefficient calculated by tensile product (referred to as the aging coefficient by tensile accumulation).