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- Author: ada
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- Date: 2014-01-18
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What is rubber, the rubber industry is the basic raw material, widely used in the manufacture of tires, hoses, plastic, cables and other various rubber products. Rubber Category:
A raw materials into the natural rubber and synthetic rubber.
2 Press the Form into lumps of raw rubber, latex, liquid rubber and rubber powder.
Latex rubber colloidal aqueous dispersion;
Liquid rubber to rubber oligomers, before unvulcanized generally as a viscous liquid;
Powder latex rubber is processed into a powder to facilitate ingredients and manufacture.
3 is divided by the use of general-purpose and special type.
Better overall performance general-purpose rubber is widely used. There are: ① natural rubber. ② isoprene rubber, also known as synthetic natural rubber. ③ SBR, referred to SBR. ④ butadiene rubber, referred to as BR.
Special rubber that contains certain special properties of rubber. Are:
① silicone rubber, referred SILICONE
Main chain composed of alternating silicon oxygen atoms with organic groups on the silicon atom. High temperature resistance, ozone resistance, electrical insulation. Operating temperature -40 ℃ ﹋ + 220 ℃; oil is preferred, temperature, abrasion resistance, oil! Especially suitable for automobile engine crankshaft oil seal is not temperature volatile oils (diesel, gasoline) Wear respect to oxygen, ozone and sunlight (UV) resistant.
② Viton. Viton
Sub-structure containing synthetic rubber fluorine atoms. Typically the number of fluorine atoms in the fluorine-containing copolymer units represented, such as fluorine rubber 23, is vinylidene fluoride with chlorotrifluoroethylene copolymer. Viton high temperature, oil, chemical resistant. Oil, high temperature resistance, chemical resistance, but also has the characteristics of acid. Temperature -30 ℃ + 280 ℃. Applicable to jet engine crankshaft oil seal, Timing seal, is also used medicament and seals and O-rings
③ neoprene, referred to CR.
By chloroprene polymerization. Has a good overall performance, oil, fire, resistance to oxidation and ozone. But its density, easy to crystallize at room temperature hardening, storage is bad, cold poor.
④ nitrile rubber, referred to as the NBR.
Butadiene and acrylonitrile copolymer obtained. Has good oil resistance, heat resistance, cold resistance, pressure resistance and water resistance, air tightness and excellent bonding properties, and has a suitable wear resistance, a usual use temperature of approximately -40 ℃ ~ + 120 ℃ , may be used in an oil or long-term 150 ℃ in air 120 ℃ in.
Ease of metal molded into an arbitrary shape hydraulic seals, so most suitable for the production of nitrile rubber is not more than 32Mpa working pressure of the hydraulic cylinder seals. Specially designed recipes, easy to press the onset of resistance to oil: when the car wear and can withstand mechanical axis speed 3000 rev / below (in this case a rubber hardness of 70 °).
⑤ Polyurethane
One of the highest tensile strength synthetic rubber, it has excellent oil resistance, heat resistance, cold resistance, pressure resistance and abrasion resistance, the usual temperature is -40 ℃ ~ + 80 ℃, polyurethane rubber sealing properties at room temperature Nitrile rubber is superior, it is particularly suitable for the production of medium pressure, high pressure and high pressure hydraulic cylinder seals.
⑥ Thiokol.
Polycondensation by polysulfide dihaloalkane with an alkali metal or alkaline earth metal together. There are excellent oil and solvent resistance, but the intensity is not high, aging resistance, workability bad smell, and with more and nitrile rubber.
In addition, urethane rubber, epichlorohydrin rubber, acrylic rubber and the like.
Characteristics of silica gel
Divided into coarse pore silica and silica pores
Silicone can adsorb moisture, but also absorb acetylene and carbon dioxide. As the temperature decreases, the first adsorbed moisture (room temperature to about 25 ℃), followed by acetylene and carbon dioxide (the lower the temperature, the adsorption capacity of the stronger).
Adsorption of water, for example size / mm4 ~ 8 at room temperature dynamic adsorption capacity / 6-8% moisture content of dried air / g • m-3 0.03 after the dry air dew point / ℃ -52
Regeneration temperature / ℃ 140 ~ 160
Silica gel adsorption capacity for water is large, the regeneration temperature is low, the price is cheap, so ASU silica gel adsorption of water is mainly used at low temperatures is also used to adsorb carbon dioxide and acetylene. The disadvantage is that the powder more.
Silicone has a rough two holes and pores, pore size difference between the two. Coarse pore silica pore size is 5 ~ 10nm (1nm = 10-9m, called Nano), the specific surface area per gram of silica gel has 100 ~ 300m2 / g as much. Its absorption ability, and not broken after absorbing water, good mechanical strength, moisture absorption used in the dryer. Pore ??silica gel pore size is 2.5 ~ 4nm, a specific surface area of ??400 ~ 600m2 / g. Used to adsorb carbon dioxide and acetylene, adsorbs moisture easily broken. The adsorption process is carbon dioxide adsorber at -110 ~ -120 ℃ low temperature, the effect of carbon dioxide is preferably adsorbed, while also capable of adsorbing acetylene. There will be less due to a temperature below -130 ℃ carbon dioxide precipitation of a solid, not only the solid carbon dioxide can not be adsorbed by silica gel, and will plug the adsorber. Adsorption of acetylene in liquid air, liquid oxygen adsorption is carried out, the adsorption temperature of about -170 ~ -180 ℃.