Recently, it was learned from the Municipal Environmental Protection Bureau that since last month, the city has started a taxi replacement of the three-way catalytic converter. It plans to replace 46,000 vehicles before the end of the year, which can reduce the emission of nitrogen oxides and volatile organic compounds by about 2,000 tons. As of yesterday, the city's 16 replacement outlets have completed the replacement of taxis three-way catalytic converters about 22,000.
Last weekend, the North China Environmental Protection Supervision Center dispatched an inspection team to conduct special inspections on the heavy-duty weather emergency response of several administrative districts in Beijing. The results show that the pollution of motor vehicles is more serious. The over-standard rate of vehicles with a vehicle age of more than 10 years is higher, and the over-standard rate of taxis with a mileage of more than 300,000 kilometers reaches 80% to 90%.
It is understood that the national motor vehicle emission standards stipulate that the three-way catalytic converter has a shelf life of 160,000 kilometers. In other words, after the gasoline car is driving 160,000 kilometers, the pollutant emissions will gradually increase. Experimental tests have shown that taxis that have been in use for more than two years can emit nitrogen oxides and volatile organic compounds more than five times and twice as much as emissions. The average pollutant emitted by a taxi that has been used for more than two years is equivalent to one year's emissions of 30 non-operating vehicles. Therefore, regular replacement of taxi three-way catalytic converter is an important measure to reduce vehicle emissions.
The relevant person in charge of the Municipal Environmental Protection Bureau revealed that since September 9, the city has fully started the work of replacing the three-way catalytic converter with a taxi. As of yesterday, the city has completed the replacement of taxis three-way catalytic converters about 22,000. It is planned to replace 46,000 vehicles before the end of the year. In fact, the three-way catalytic converter is an off-board purification device installed in the exhaust system of an automobile, which converts carbon monoxide, hydrocarbons and nitrogen oxides discharged from automobile exhaust into carbon dioxide, water and oxidation by oxidation and reduction. Nitrogen gas purifies the car's exhaust.
In order to ensure the smooth implementation of the replacement work, the transportation, environmental protection, public security, quality supervision and other departments have formulated specific implementation organization plans and detailed the implementation plan. More than 40,000 vehicles to be replaced with three-way catalytic converters will be assigned to each of the operating units, each driver, each vehicle, and each of the 16 replacement outlets and 98 three-way catalytic replacement special stations. Hours, each outlet. (Reporter Wang Bin)
At present, the five most commonly used thermosetting plastics in various fields are PU, epoxy resin (EP), silicone, unsaturated polyester (UP) and phenolic resin (PF).
Thermosetting plastic has the following advantages:
Thermosetting plastic has a large rigidity and is extremely elastic and plastic deformation.The temperature has little influence on stiffness, and under the same load and temperature, the creep variable is much smaller than thermoplastic.Good heat resistance;The plastic parts are quite stable when heated.The size of the plastic parts is good. Thermosetting plastic is less affected by temperature and humidity, and Thermosetting plastic can be reduced after forming, making Thermosetting plastic easy to make plastic parts with high precision than thermoplastic ruler.Excellent electrical performance.Resistance to arc and voltage, etc.Good corrosion resistance, weak acid, weak base and organic solvents;Good processability, can be processed by various molding methods and other advantages.
Most thermosetting plastics have the following characteristics:
(1) excellent chemical resistance.
(2) it is usually brittle hard plastic, which can be filled with various fillers to form composite materials.
(3) compared with thermoplastic resin, the molding cycle is longer.
(4) all kinds of modification can be carried out, depending on the combination of resin, crosslinking agent, additive, etc., which can form composite materials with different properties.
(5) good heat resistance, the use of high temperature, Tg of thermosetting polyimide (PI) is about 350 ℃.
(6) can be used as raw materials to meet the application of various fields.Only 5% is used as injection molding material.
(7) the waste is generally used as filler after pulverization, which is difficult to recycle and pollutes the environment.
Due to the high heat resistance of thermosetting plastic, good dimensional stability, good line performance, anti-aging properties are better than thermoplastic plastic and low price, so it is widely used.The disadvantage is that the mechanical properties are poor and need to be enhanced.
It is mainly composed of thermosetting resins, which are involved in various necessary additives to form the plastic of the products.In the process of manufacturing or forming, the liquid will be liquid, which will not melt after curing or melt or soften again.Common thermosetting plastics include phenolic plastic, epoxy plastic, amino plastic, unsaturated polyester, alkyd plastics, etc.Thermosetting plastic and thermoplastic plastics constitute two major components of synthetic plastic.
Thermosetting plastic heating for the first time can soften the flow, heated to a certain temperature, react a crosslinking reaction and curing hardens, this change is irreversible, since then, heating again, already no longer soft flow.It is the use of this characteristic to make the molding process, using the plasticization flow of the initial heating, filling the cavity under pressure, and solidifying to become the product that determines the shape and size.
Thermosetting plastic is distinguished by a chemical reaction that is hardened by heating, pressing or adding the hardener at a definite temperature.After hardening, plastic chemical structure changes, the texture is hard, dissolves in the solvent, heating also no longer softens, if the temperature is too high then decompose.In thermoplastic plastic, the chains of resin molecules are linear or branched, and there is not any chemical bond between the molecular chains, which soften the flow when heated.The process of cooling and hardening is a physical change.
Formaldehyde cross linked plastic includes phenolic plastic, amino plastic (such as urea-formaldehyde - melamine - formaldehyde, etc.).Other cross linked types of plastic include unsaturated polyester, epoxy resin, prevalence, diallyl ester resin, etc.
The commonly used thermosetting plastics are phenolic resin, urea-formaldehyde resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, polyurethane, etc.
Production:Phenolic resin PF (Bakelite sheet)
Phenolic resin is a part of the longest plastic varieties in history, commonly known as bakelite or electric wood, and the appearance is yellowish or black, which is the typical representative of thermosetting plastic.Bakelite sheet molding often use a variety of filling materials, according to different filling materials used, the product performance is also different, Bakelite sheet as molding material, mainly used in the field of need heat resistance, but also as a bonding agent used in plywood, grinding wheel and the brake pads.
Thermosetting Plastic,Thermoset Molding Plastic,Mould Thermosetting Plastic,Thermoplastic Type Plastic
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