Nitrile rubber is mainly used to make oil-resistant rubber products. A synthetic rubber made of butadiene and acrylonitrile. It is a synthetic rubber with good oil resistance (especially alkane oil) and aging resistance. There are five kinds of acrylonitrile content (%) in NBR: 42 ~ 46, 36 ~ 4 1, 3 1 ~ 35, 25 ~ 30, 18 ~ 24. The higher the acrylonitrile content, the better the oil resistance, but the lower the cold resistance.
It can be used in air at 120℃ or oil at 150℃ for a long time. In addition, it also has good water resistance, air tightness and excellent adhesion. It is widely used to make all kinds of oil-resistant rubber products, all kinds of oil-resistant gaskets, washers, sleeves, soft packages, hoses, printing and dyeing cots, cable rubber materials and so on. , has become an indispensable elastic material in automobile, aviation, petroleum, photocopying and other industries. ?
Basic performance? NBR has excellent oil resistance, second only to polysulfide rubber and fluororubber, and has good wear resistance and air tightness. The disadvantage of Ding Qing rubber is that it is not resistant to ozone, aromatic hydrocarbons, halogenated hydrocarbons, ketones and esters, so it is not suitable for insulating materials. ?
Main uses NBR is mainly used to make oil-resistant products, such as oil-resistant pipes, adhesive tapes, rubber diaphragms and large oil bags. It is often used to make various oil-resistant molded products, such as O-rings, oil seals, leather cups, diaphragms, valves, corrugated pipes, etc. It is also used to make rubber plates and wear-resistant parts. ?
Nitrile rubber is very polar, and its compatibility with other polymers is generally not very good, but it has good compatibility with high polar polymers such as chloroprene rubber, modified phenolic resin and polyvinyl chloride, especially with chlorine-containing polymers, and is often used in combination. In addition, NBR is often used with nonpolar rubber such as natural rubber, styrene-butadiene rubber and cis-butadiene rubber in order to improve processability and usability. It should be pointed out that NBR is characterized by good oil resistance, and the oil resistance tends to decrease when it is used with other polymers (except PVC).
2. Synthetic rubber with fluorine atoms in its molecular structure is a kind of special rubber with high temperature resistance, oil resistance and chemical corrosion resistance. There are many kinds, usually expressed by the number of fluorine atoms in fluorine-containing units in * * * polymers. For example, fluororubber 23 is a polymer of vinylidene fluoride and chlorotrifluoroethylene, fluororubber 246 is a polymer of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, and fluororubber 26 is a polymer of vinylidene fluoride and hexafluoropropylene.
Fluorocarbon 26 is a white, odorless, nontoxic and nonflammable solid with outstanding characteristics of high temperature resistance, chemical corrosion resistance, oil resistance and oxidation resistance. It can be used for a long time at 250℃ and for a short time at 300℃. The tensile strength of its vulcanizate is 7.0 ~ 17.5 MPa and the elongation is 150% ~ 300%. It has weather resistance, ozone resistance, excellent electrical insulation and lower air permeability than other rubbers. The strong oxidation resistance of fluororubber 23 is outstanding. The main disadvantages of fluororubber are poor low temperature resistance, high density and high price.
Uses fluororubber is essential in aviation, aerospace, automobile, petroleum, petrochemical industry and industrial pollution control? Special synthetic rubber, mainly used to manufacture gaskets, sealing rings and other seals with high temperature resistance, oil resistance and chemical corrosion resistance; Secondly, it is used to make rubber hoses, impregnated products and protective articles.
3. The molecular skeleton of silica gel is composed of silicon atoms and oxygen atoms alternately, which is a polymer elastic material with both inorganic and organic properties. At present, the most widely used is methyl vinyl silicone rubber, which is polymerized by dimethyl siloxane and a small amount of vinyl siloxane.
Silica gel is a colloidal substance with solid characteristics, and its basic component is silicon dioxide (SiO2). The physical structure of silica gel is rich in micropores, with large specific surface area and silicon hydroxyl structure on the surface, so it has strong adsorption and selective adsorption and separation ability for water vapor or other polar substances, and is widely used in the fields of adsorption, drying, separation, purification and preparation of high-purity substances. In the field of chemical engineering, silica gel can be used as catalyst or catalyst carrier.
Due to its chemical composition and physical structure, silica gel has the following advantages in application:
(1) is chemically stable and insoluble in any other solvents and solutions except hydrofluoric acid (HF) and strong alkali;
(2) Good thermal stability. A-type fine pore silica gel can be used at a temperature below 300℃, and other types of silica gel can be used for a long time at a high temperature of 500-600℃;
(3) Silica gel has a rigid skeleton structure, good wear resistance and compressive strength.
Each variety of silica gel series products has its own characteristics, because different types of pore structures can be obtained by controlling the corresponding process conditions in the manufacturing process of silica gel to adapt to different application fields.
Extended data:
Key application of fluororubber: Because fluororubber has the characteristics of high temperature resistance, oil resistance, high vacuum, acid and alkali resistance and various chemicals resistance, it is used in modern aviation, missiles, rockets, aerospace, ships, atomic energy and other cutting-edge technologies and industrial fields such as automobiles, shipbuilding, chemistry, petroleum, telecommunications, instruments and machinery.
Typical application of fluororubber;
When the fluororubber seal is used to seal the engine, it can work at 200℃~250℃ for a long time and 300℃ for a short time, and its service life can be the same as the engine repair life, reaching 1000~5000 flight hours (time 5~ 10 year).
When used in chemical industry, it can seal inorganic acids (such as 67% sulfuric acid at 140℃, concentrated hydrochloric acid at 70℃ and 30% nitric acid), organic solvents (such as chlorinated hydrocarbons, benzene and high aromatic gasoline) and other organic substances (such as butadiene, styrene, propylene, phenol and fatty acids at 275℃).
When used in deep well oil production, it can withstand the harsh working conditions of 149℃ and 420 atmospheric pressure; When used for superheated steam sealing, it can work in the steam medium of 160~ 170℃ for a long time. In the production of monocrystalline silicon, fluororubber seals are often used to seal special media at high temperature (300℃)-trichlorosilane, silicon tetrachloride, gallium arsenide, phosphorus trichloride, trichloroethylene and 120℃ hydrochloric acid.
In the application of high vacuum, the air pressure is133x10-6pa (10-6mmhg) at the flying height of 200~300Km, and chloroprene rubber, polybutadiene rubber and butyl rubber can be applied.
When the flying altitude exceeds 643Km, the air pressure will drop below133 x10-7pa (10-7mmhg), and only fluororubber can be used in this high vacuum. Usually, high vacuum or ultra-high vacuum equipment systems need high temperature baking treatment. Type 26 and 246 fluororubbers can withstand high temperature aging at 200℃~250℃, so they become the most important rubber materials in high vacuum equipment and spacecraft.
The hose made of fluororubber is suitable for conveying and guiding high temperature, oil and special media, such as aircraft fuel, hydraulic oil, synthetic diester oil, high temperature hot air, hot inorganic and other special media (such as chlorinated hydrocarbons and other chlorides). Wires and cables made of fluororubber have good flexibility and good insulation. Glass fiber adhesive tape made of fluororubber is resistant to high temperature of 300℃ and chemical corrosion.
After being coated with fluorine glue, aramid cloth can be used to manufacture telescopic pipes (both ends can be connected with metal flanges) between high-temperature and acid-base storage tanks in petrochemical plants, which can withstand high pressure, high temperature and medium corrosion, and play a role in buffering and damping the deformation and expansion of the two storage tanks. The adhesive tape sealing bag made of nylon cloth coated with fluorine rubber is used as the soft seal of floating roof storage tank in refinery, which plays a role in sealing and reducing the volatile loss of oil level.
23-type and 4-type propylene fluororubber are mainly used for sealing occasions with acid resistance and corrosion resistance of special chemicals. Hydroxynitroso fluororubber is mainly used as protective products and sealing products, and as a non-combustible coating in solution form, it is applied to fire-proof electronic components working in pure oxygen.
Its solution and liquid rubber can be sprayed and poured into many products, such as spacesuits, gloves, pipe belts, balls and so on. It can also be used as an adhesive for glass, metal and fabric, and can be used to make sponges, gaskets, O-rings, capsules, valve seals and other seals that contact with rocket propellant (N2O4).
References:
Baidu encyclopedia-fluorine glue