Rubber, together with plastic and fiber, is called the three major synthetic materials, and is the only polymer material with high elasticity and excellent elasticity. The biggest feature of rubber is that the modulus of elasticity is very small and the elongation is very high. The second is that it has fairly good gas permeability resistance, resistance to various chemical media and electrical insulation properties. Some special synthetic rubbers have better oil resistance and temperature resistance, and can resist the swelling of fatty oil, lubricating oil, hydraulic oil, fuel oil and solvent oil; cold resistance can be as low as -60 ° C to -80 ° C, heat resistance can be High to +180°C to +350°C. Rubber is also resistant to various flexures and bending deformations because of the small hysteresis loss. The third characteristic of rubber is that it can be used, blended and compounded with various materials, and thus modified to obtain good comprehensive properties.
These basic properties of rubber make it an excellent shock absorbing, sealing, flexing, wear-resistant, anti-corrosion, insulating and bonding material in industry.
1. Types, properties and uses of rubber
In the world, there are more than 100 types of rubber (including plastic-modified elastomers). If estimated by grade, there are actually more than 1,000 kinds.
1. Classification of rubber
(1) According to the source and method of raw materials
Rubber can be divided into two categories: natural rubber and synthetic rubber. Among them, the consumption of natural rubber accounts for 1/3, and the consumption of synthetic rubber accounts for 2/3.
(2) According to the appearance of rubber
Rubber can be divided into four categories: solid rubber (also known as dry rubber), emulsion rubber (referred to as latex), liquid rubber and powder rubber.
(3) According to the properties and uses of rubber
In addition to natural rubber, synthetic rubber can be divided into general synthetic rubber, semi-general synthetic rubber, special synthetic rubber and special synthetic rubber.
(4) According to the physical form of rubber
Rubber can be divided into hard rubber and soft rubber, raw rubber and mixed rubber, etc.
According to the type of rubber and the form of crosslinking, in industrial use, rubber can be classified as follows.
The first category is divided into heat-resistant and oil-resistant functions: ordinary rubber, heat-resistant rubber, oil-resistant rubber, weather-resistant rubber, and rubber resistant to special chemical media.
The other category is divided into: general rubber, hard rubber, semi-hard rubber, hard rubber, microporous rubber, sponge rubber, foam rubber, etc. according to the hardness of the rubber.
2. Varieties, characteristics and uses of commonly used rubber
Varieties, characteristics and uses of commonly used rubber
Rubber Variety
1. Natural rubber
(NR) is mainly rubber hydrocarbon (polyisoprene), containing a small amount of protein, water, resin acid, sugar and inorganic salt. High elasticity, high elongation strength, excellent tear resistance and electrical insulation, good wear resistance and drought resistance, good processability, easy to bond with other materials, and is superior to most synthetic rubbers in terms of comprehensive performance. The disadvantages are poor oxygen and ozone resistance, easy aging and deterioration; poor oil and solvent resistance, low acid and alkali corrosion resistance; low heat resistance. Operating temperature range: about -60℃～+80℃. Making tires, rubber shoes, rubber hoses, tapes, insulation layers and sheaths for wires and cables, and other general products. Especially suitable for the manufacture of torsional vibration dampers, engine shock absorbers, machine mounts, rubber-metal suspension elements, diaphragms, molded products.
2. SBR
(SBR) Copolymer of butadiene and styrene. Its performance is close to that of natural rubber, and it is the most widely used synthetic rubber at present. Its characteristics are that its wear resistance, aging resistance and heat resistance exceed natural rubber, and its texture is more uniform than natural rubber. The disadvantages are: low elasticity, poor flex and tear resistance; poor processing performance, especially poor self-adhesiveness and low raw rubber strength. Operating temperature range: about -50℃～+100℃. It is mainly used to replace natural rubber to make tires, rubber sheets, rubber hoses, rubber shoes and other general products.
3. Butadiene rubber
(BR) is a cis-structured rubber polymerized from butadiene. The advantages are: excellent elasticity and wear resistance, good aging resistance, excellent low temperature resistance, low calorific value under dynamic load, and easy metal bonding. The disadvantages are low strength, poor tear resistance, poor processing performance and self-adhesiveness. Operating temperature range: about -60℃～+100℃. Generally, it is used together with natural rubber or styrene-butadiene rubber to make tire treads, conveyor belts and special cold-resistant products.
4. Isoprene rubber
(IR) is a cis-structured rubber polymerized from isoprene monomer. The chemical composition and three-dimensional structure are similar to natural rubber, and the performance is very close to natural rubber, so it is called synthetic natural rubber. It has most of the advantages of natural rubber, aging resistance due to natural rubber, slightly lower elasticity and strength than natural rubber, poor processing performance, and high cost. Operating temperature range: about -50℃～+100℃ It can replace natural rubber to make tires, rubber shoes, hoses, tapes and other general products.
5. Neoprene
(CR) is a polymer formed by emulsion polymerization of chloroprene monomer. This rubber molecule contains chlorine atoms, so compared with other general-purpose rubbers: it has excellent anti-oxidation, anti-ozone, non-flammable, self-extinguishing after fire, oil resistance, solvent resistance, acid and alkali resistance, and aging and gas resistance. Good tightness and other advantages; its physical and mechanical properties are also better than natural rubber, so it can be used as general rubber or special rubber. The main disadvantages are poor cold resistance, large specific gravity, high relative cost, poor electrical insulation, and easy sticking, scorching and mold sticking during processing. In addition, raw rubber has poor stability and is not easy to store. Operating temperature range: about -45℃～+100℃. Mainly used in the manufacture of cable sheaths and various protective covers and protective covers that require high ozone resistance and aging resistance; oil-resistant and chemical-resistant hoses, tapes and chemical linings; flame-resistant rubber products for underground mining, and various moldings Products, sealing rings, gaskets, adhesives, etc.
6. Butyl rubber
(IIR) is a copolymer of isobutylene and a small amount of isoprene or butadiene. The biggest feature is good air tightness, good ozone resistance, aging resistance, high heat resistance, long-term working temperature can be below 130 ° C; ability to resist inorganic strong acids (such as sulfuric acid, nitric acid, etc.) and general organic solvents, vibration absorption and damping characteristics Good, and electrical insulation is also very good. The disadvantages are poor elasticity, poor processing performance, slow vulcanization speed, poor adhesion and oil resistance. Operating temperature range: about -40℃～+120℃. Mainly used as inner tubes, water tires, balloons, wire and cable insulation layers, chemical equipment linings and shockproof products, heat-resistant conveyor belts, heat-resistant and aging-resistant tape products.
7. NBR
(NBR) Copolymer of butadiene and acrylonitrile. It is characterized by excellent resistance to gasoline and aliphatic hydrocarbon oils, second only to polysulfide rubber, acrylic ester and fluororubber, and better than other general-purpose rubbers. Good heat resistance, good air tightness, wear resistance and water resistance, etc., and strong adhesion. The disadvantages are poor cold resistance and ozone resistance, low strength and elasticity, poor acid resistance, poor electrical insulation, and poor resistance to polar solvents. Operating temperature range: about -30℃～+100℃. Mainly used in the manufacture of various oil-resistant products, such as rubber hoses, sealing products, etc.
8. Hydrogenated nitrile rubber
(HNBR) Copolymer of butadiene and acrylonitrile. It is obtained by fully or partially hydrogenating the double bonds in butadiene of NBR. It is characterized by high mechanical strength and wear resistance, better heat resistance than NBR when crosslinked with peroxide, and other properties are the same as NBR. The disadvantage is that the price is higher. Operating temperature range: about -30℃～+150℃. Mainly used for oil-resistant, high-temperature-resistant sealing products.
9. Ethylene Propylene Rubber
(EPM\EPDM) Copolymer of ethylene and propylene, generally divided into two-dimensional ethylene-propylene rubber and three-dimensional ethylene-propylene rubber. It is characterized by excellent ozone resistance, ultraviolet resistance, weather resistance and aging resistance, ranking first among general-purpose rubbers. Good electrical insulation, chemical resistance, impact elasticity, acid and alkali resistance, small specific gravity, and high filling and matching. Heat resistance up to 150 ° C, resistance to polar solvents - ketones, esters, etc., but not resistant to aliphatic hydrocarbons and aromatic hydrocarbons, other physical and mechanical properties are slightly inferior to natural rubber and better than styrene-butadiene rubber. The disadvantage is that the self-adhesion and mutual adhesion are very poor, and it is not easy to bond. Operating temperature range: about -50℃～+150℃. Mainly used as chemical equipment lining, wire and cable sheath, steam hose, heat-resistant conveyor belt, rubber products for automobiles and other industrial products.
10. Silicone rubber
(Q) Special rubber containing silicon and oxygen atoms in the main chain, among which the silicon element plays a major role. Its main features are high temperature resistance (up to 300°C) and low temperature resistance (minimum -100°C). It is currently the best cold and high temperature resistant rubber; at the same time, it has excellent electrical insulation and high stability to thermal oxidation and ozone. , chemically inert. The disadvantage is that the mechanical strength is low, oil resistance, solvent resistance and acid and alkali resistance are poor, it is difficult to vulcanize, and the price is more expensive. Operating temperature: -60℃～+200℃. It is mainly used to make high and low temperature resistant products (hose, seals, etc.), high temperature resistant wire and cable insulation layer, because it is non-toxic and tasteless, it is also used in food and medical industries.
11. Fluorine rubber
(FPM) is an organic elastomer formed by copolymerization of fluorine-containing monomers. Its characteristics are high temperature resistance up to 300 ℃, acid and alkali resistance, oil resistance is the best in oil resistant rubber, good radiation resistance and high vacuum resistance; electrical insulation, mechanical properties, chemical corrosion resistance, ozone resistance and atmospheric resistance All were excellent in aging properties. The disadvantages are poor processability, high price, poor cold resistance, and low elasticity and air permeability. Operating temperature range: -20℃～+200℃. It is mainly used in the defense industry to manufacture vacuum-resistant, high-temperature-resistant, chemical-resistant sealing materials, hoses or other parts on aircraft and rockets, and in the automotive industry.
12. Polyurethane rubber
(AU\EU) There are elastomers polymerized from polyester (or polyether) and diisocyanate compounds. It is characterized by good wear resistance, which is the best among all kinds of rubber; high strength, good elasticity, and excellent oil resistance. It is also excellent in ozone resistance, aging resistance, airtightness and the like. The disadvantage is poor temperature resistance, poor water and alkali resistance, poor resistance to aromatic hydrocarbons, chlorinated hydrocarbons and ketones, esters, alcohols and other solvents. Operating temperature range: about -30℃～+80℃. The production of tires consists of parts, gaskets, anti-vibration products, and rubber products that are wear-resistant, high-strength and oil-resistant.
13. Acrylic rubber
(ACM\AEM) It is a polymer of ethyl acrylate or butyl acrylate. It is characterized by good heat resistance and oil resistance, and stable performance in lubricating oils containing sulfur, phosphorus and chlorine additives. At the same time, it is resistant to aging, oxygen and ozone, ultraviolet rays, and has excellent air tightness. The disadvantage is that it has poor cold resistance, no water resistance, no resistance to steam, organic and inorganic acids and alkalis. It swells severely in water-soluble solutions such as methanol, ethylene glycol, and ketone esters. At the same time, the elasticity and wear resistance are poor, the electrical insulation is poor, and the processing performance is poor. Operating temperature range: about -25℃～+150℃. It can be used to manufacture oil-resistant, heat-resistant, and aging-resistant products, such as seals, hoses, chemical linings, etc.
14. Chlorosulfonated polyethylene rubber
(CSM) It is an elastic polymer obtained after polyethylene is chlorinated and sulfonated. Excellent ozone resistance and aging resistance, and better weather resistance than other rubbers. Flame retardant, heat resistance, solvent resistance and resistance to most chemicals and acid and alkali resistance are good. The electrical insulation is acceptable, and the wear resistance is similar to that of styrene-butadiene rubber. The disadvantage is that the tear resistance is poor and the processing performance is not good. Operating temperature range: about -20℃～+120℃. It can be used as a sealing material on an ozone generator, to manufacture oil-resistant seals, wire and cable sheaths, oil-resistant rubber products and chemical linings.
15. Chlorine ether rubber
(CO\ECO) A polymer formed by the homopolymerization of epichlorohydrin or the copolymerization of epichlorohydrin and ethylene oxide. It is characterized by excellent resistance to aliphatic hydrocarbons and chlorinated hydrocarbon solvents, alkali resistance, water resistance, aging resistance, ozone resistance, weather resistance close to heat, and high air tightness. The disadvantages are low strength, poor elasticity, and poor electrical insulation. Operating temperature range: about -40℃～+140℃. It can be used as rubber hose, seal, film and container lining, oil tank, rubber roller, and manufacture oil seal, water seal, etc.
16. Chlorinated polyethylene rubber
(CM or CPE) is an elastic polymer made of polyethylene through chlorine substitution reaction. The performance is close to that of chlorosulfonated polyethylene rubber. It is characterized by good fluidity and easy processing; it has excellent weather resistance, ozone resistance and corona resistance, and good heat resistance, acid and alkali resistance, and oil resistance. The disadvantages are poor elasticity, large compression deformation, and low electrical insulation. Operating temperature range: about -20℃～+120℃. Wire and cable sheaths, rubber hoses, adhesive tapes, chemical linings for rubber rollers, etc.
3. Types of rubber industrial products
Rubber industrial products are rubber products other than tires, hoses, tapes, etc. Mainly include the following categories.
1. Rubber sealing products
Rubber sealing products include O-shaped rubber sealing rings, rotating shaft lip seals (oil seals), composite seals, rubber seals with special-shaped sections, brake cup aprons, rubber diaphragms for automobile brake chambers, rubber sealing strips, rubber anti-corrosion Dust cover (cover), film, water seal products, water-absorbing rubber, bridge deck rubber expansion joints, etc.
2. Rubber shock-absorbing products
Rubber damping products include rubber shock absorbers, rubber gas springs, rubber elastic couplings, flexible rubber joints, rubber fenders, rubber shock absorbers for automobiles, rubber shock absorbers for train locomotives, rubber sleeper pads, bridges Rubber bearings, etc.
3. Hard rubber
4. Rubber sponge products
5. Rubber sheet and waterproof membrane
6. Rubber roller
7. Textile rubber products
8. Rubber products for printing industry
9. Rubber lining
10. Rubber electrical insulation products
12. Cork rubber
4. Properties and determination of rubber
The performance of vulcanized rubber mainly refers to mechanical properties, heat resistance, cold resistance, medium resistance, wear resistance, weather aging resistance, flame retardancy and electrical insulation properties, etc., which are decisive for the performance and product quality of rubber products. Impact.
The performance of vulcanized rubber is closely related to its formula composition. Choosing different formula composition can make the properties of vulcanized rubber change in a wide range. Therefore, studying the relationship between performance and formulation components is one of the main contents of formulation design.
The properties of rubber can be divided into two categories, structural properties and functional properties. Structural properties refer to mechanical properties such as high elasticity and strength; functional properties refer to the physical and chemical properties of rubber, such as medium resistance, electrical insulation, and chemical resistance. Corrosive etc. Among rubber products, some mainly use the former type of performance, such as shock absorbing products, sealing products, etc.; some use the latter type of performance mainly, such as water seal (water resistance) and cable sheath (electrical insulation) wait. But among all the properties, structural properties and mechanical properties are the most important. Because it is the foundation of all performance.