Rubber is divided into natural rubber and synthetic rubber. Natural rubber mainly from the clover rubber tree, when the skin of the rubber tree is cut, it will flow out of milky white juice, known as latex, latex by the cohesion, washing, forming, drying that is natural rubber. Synthetic rubber is made by artificial synthesis method, using different raw materials (monomer) can be synthesized into different types of rubber. 1900 ~ 1910 chemist C.D. Harris (Harris) measured the natural rubber structure is isoprene polymer, which opens up a way for synthetic rubber. 1910 Russian chemist SV Lebedev (Lebedev, 1874-1934) with sodium sodium as the initiator of 1,3-butadiene polymerization of sodium butadiene rubber, and later appeared in a number of new varieties of synthetic rubber, such as Shun Butadiene rubber, neoprene, styrene butadiene rubber and so on. Synthetic rubber production has been much higher than natural rubber, which is the largest production of styrene butadiene rubber.
Tires and general industrial rubber products. General rubber demand, is the main varieties of synthetic rubber.
Shoes and so on. The shortcomings of butadiene rubber is the tear resistance of the poor, anti-slippery performance is not good.
Oil resistance and styrene butadiene rubber close. Ethylene-propylene rubber is widely used, can be used as tire sidewall, tape and tube and car parts, but also for the wire, cable foreskin and high pressure, ultra-high pressure insulation material. Can also manufacture shoes, health supplies and other light-colored products.
Hoses, washers and chemical resistant linings.
The general structure of vulcanized rubber. Due to the large molecular weight, no external force, was fine group. When the external force, the removal of external forces, fine group of entanglement changes, the molecular chain rebound, resulting in a strong tendency to restore, which is the origin of high elastic rubber.
Branches: The chains of rubber macromolecules are clustered to form gels. The gel is detrimental to the performance and processing of the rubber. In the refining of rubber, a variety of complexing agent is often progressing the gel area, the formation of local blank, can not form reinforcement and cross-linking, as the weak parts of the product.
Crosslinking structure: Linear molecules through some atoms or atomic groups of the bridge and connected to each other to form a three-dimensional network structure. With the progress of the vulcanization process, this structure has been strengthened. In this way, the free activity of the segment decreases, the plasticity and elongation decrease, the strength, the elasticity and the hardness rise, and the compression set and the degree of swelling decrease.
The advantages and disadvantages of each classification of rubber material and use
Natural rubber NR (Natural Rubber)
It is made of rubber latex and is a polymer of isoprene with good abrasion resistance, high elasticity, breaking strength and elongation. Aging in the air, Oil or gasoline in the expansion and dissolution, alkali-resistant but not strong acid. Advantages: good elasticity, acid and alkali. Disadvantages: not weather, not resistant to oil (resistant to vegetable oil) is the production of tape, hose, rubber shoes and raw materials, and for the production of shock absorber parts, in the car brake oil, ethanol and other products used in the liquid hydroxide.
SBR (Styrene Butadiene Copolymer)
Butadiene and styrene copolymer, compared with natural rubber, uniform quality, less foreign body, with better wear resistance and aging resistance, but the mechanical strength is weak, can be used with natural rubber blending. Advantages: low-cost non-oil resistant material, good water resistance, hardness of 70 or less with good elasticity, high hardness with poor compression, Disadvantages: do not recommend the use of strong acid, ozone, oil, oil and fat and large Part of the hydrocarbons. Widely used in the tire industry, footwear, cloth industry and conveyor belt industry.
Butyl Rubber IIR (Butyl Rubber)
Isobutylene and a small amount of isoprene polymerization, because the methyl-dimensional barrier molecules than other polymers less movement, so less gas permeability, heat, sunlight, ozone resistance, electrical insulation good ; The resistance of the polar agent, the general use of temperature range of -54-110 ° C. Advantages: for most of the general gas is impermeable to the sun and smelly with good resistance can be exposed to animal or vegetable oil or Is a gasifiable chemical. Disadvantages: It is not advisable to use inner tubes, purses, rubber paste paper, window frame rubber, steam hose, heat-resistant conveyor belt, etc. for automotive tires with petroleum solvents, kerosene and aromatic hydrogen
Hydrogenated Nitrile HNBR (Hydrogenate Nitrile)
Hydrogenated Dingqing rubber for Dingqing gum after hydrogenation to remove part of the double chain, after hydrogenation of its temperature resistance, weatherability than the general increase in a lot of NBR, oil resistance and general Dingqing plastic similar. General use temperature range of -25 ~ 150 ℃. Advantages: better than Dingqing plastic wear resistance, with excellent resistance to corrosion, tensile, tear resistance and compression characteristics
In the ozone and other atmospheric conditions with good resistance, generally applicable to laundry or dishwashing cleaning agent. Disadvantages: It is not recommended for use in alcohols, esters or aromatic solutions in the air-conditioning refrigeration industry, widely used in environmentally friendly refrigerant R134a system seals.
Automotive engine system seals.
EPDM (Ethylene propylene Rubber)
From ethylene and propylene copolymerization, so heat resistance, aging resistance, ozone resistance, stability are very good, but can not sulfur sulfur. To solve this problem, in the EP main chain into a small amount of double-stranded The third component can be added sulfur into EPDM, the general use of the temperature of -50 ~ 150 ° C. Polar solvents such as alcohol, ketones and other excellent resistance: good resistance to weather and ozone resistance, with excellent Water resistance and anti-chemical objects, can use alcohol and ketones, high temperature steam, the gas with good impermeability. Disadvantages: Not recommended for food use or exposure to aromatic hydrogen. Seals or parts of sanitary ware for high temperature water vapor. Brake (brake) system in the rubber parts. A seal in a radiator (car water tank).
NBR (Nitrile Rubber)
From the acrylic and butadiene copolymerization, the acrylic surface content from 18% to 50%, the higher the content of propylene, the petrochemical oil hydrocarbon fuel oil resistance is better, but the low temperature performance is worse, the general The use of temperature range of -25 ~ 100 ℃. NBR is one of the most commonly used rubber for oil seals and O-rings. Advantages: Good resistance to oil, water resistance, solvent resistance and anti-high pressure oil
With good compression, anti-wear and elongation.
Disadvantages: Not suitable for use in polar solvents such as ketones, ozone, nitrohydrocarbons, MEK and chloroform. For the production of fuel tanks, lubricating tanks and oil in the hydraulic oil, gasoline, water, silicone oil, Lubricants and other fluid medium used in the rubber parts, especially the sealing parts can be said that the most widely used, the lowest cost rubber seals
Neoprene CR (Neoprene, Polychloroprene)
From chlorinated butadiene monomer polymerization. After vulcanization of rubber elastic wear resistance, not afraid of direct sunlight, there are particularly good weathering performance, not afraid of intense distortion, not afraid of refrigerant, resistant to acid, resistant to silicon Lubricating oil, but not resistant to phosphoric acid ester hydraulic oil. At low temperature easy to crystallization, hardening, storage stability is poor, low in the mineral point of mineral oil in the expansion of large. General use temperature range of -50 ~ 150 ° C. Advantages: Elasticity and good compression deformation, the formula does not contain sulfur is very easy to produce. With anti-animal and vegetable oil characteristics, not because of neutral chemicals, fat, grease, a variety of oil, solvent and physical properties, With fire resistance.
Disadvantages: It is not recommended to use strong acids, nitrohydrocarbons, esters, chloroform and ketone chemicals in the resistance of R12 refrigerant seals, household appliances on the rubber parts or seals. Suitable for the production of a variety of direct contact with the atmosphere, sunlight, ozone parts. Applicable to all kinds of fire-resistant, chemical-resistant rubber products.
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