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Discuss environmental characteristics of wire and cable

Release date:2013-07-15
Hazardous substances requirements. Currently called ordinary wire and cable is environmentally friendly lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers content within the provisions of the EU RoHS cables. And wire and cable shall not contain environmental hormones, non-contaminated soil and water. Flame retardant, environmentally friendly flame retardant wire and cable better performance in the face of flames and fire, to prevent the rapid spread of flames and spread its control in limited areas, to minimize losses. Senior environmental retardant wire: is environmentally friendly halogen-free flame-retardant wire, not only in full compliance with general environmental retardant wire requirements, and halogen-free, combustion does not produce harmful gases and corrosive gases. According to the requirements of environmental protection, flame retardant wires without reducing flammability rating guarantee under the premise of the gases released during combustion characteristics with low smoke, halogen-free, low toxicity characteristics. Fire, to ensure that all staff have the opportunity to escape, visual distance of not less than 15m, some environmentally friendly wire and cable fire smoke can be achieved when the visual distance of 97m, while the general cable is only 5 ~ 8m. Usually burned cable insulation, senior environmental protection wire is white smoke emitted mainly water vapor and small amounts of smoke. 
   Temperature levels increased carrying capacity increases. An ordinary PVC wire temperature rating is 70 ℃, while the green wire temperature was 105 ℃, 125 ℃, 150 ℃, higher than ordinary cables 30 ℃ ~ 60 ℃. After the tests, the same environmental specifications section of conductor ampacity than ordinary wire can be increased by 30% to 50%, and increase the degree of crosslinking can even reach 80%. Environmentally friendly halogen-free wire is usually crosslinked products, in recent years, the cable industry commonly used radiation crosslinking technology, nuclear technology through specific energy electron irradiation processing, the molecular structure of polyolefin material from the original linear structure into a mesh structure, this process can be improved and the operating temperature of the cable resistance instantaneous short-circuit capacity of the high traffic load, greatly increased temperature levels. Although senior environmental retardant wire increased costs, but taking into account the increase in carrying capacity, cost-effective high-level green wire, that is the same carrying capacity, senior environmental retardant wire costs lower prices. 
   So, environmentally friendly development status of wire and cable how to do? 
   In the 1980s started to develop the international wire and cable LSZH material, this material has the advantage of low smoke, non-toxic, is fire burning, the resulting metal oxides and water vapor. Halogen-halogen flame-retardant polyolefin is a polyolefin as the matrix, it will be EVA (ethylene - vinyl acetate copolymer), a large number of activated magnesium hydroxide or aluminum hydroxide kneaded in a polyethylene matrix, and the use of hydroxide Combustion heat, the decomposition into metal oxide and water, to achieve the purpose of fire. The reaction formula is as follows: 
   Mg (OH) 2 → MgO + H2O heat 
   2Al (OH) 3 → Al2O3 +3 H2O heat 
   is the use of halogen flame-retardant polyolefin and a metal oxide oxygen-absorbing method to fire , and its flame retardant mechanism: first wire and cable fire, the surface hydroxide decomposition reaction which is an endothermic reaction, absorbing a lot of heat in the ambient air, reducing the temperature of the surface of wire and cable; Second, the water formed molecules, also absorbed a lot of heat the surface of wire and cable, but also cut off oxygen to water vapor; three is to produce metal oxide crusts, preventing oxygen and organic matter in contact again. 
   Developed in the 1980s has developed a low-smoke halogen-free cable, and strongly recommend to use this harmless wires and cables to replace and gradually abandoned the use of toxic PVC wire and cable. This means that halogen-containing cables released in the fire toxicity is very terrible, if in 30 minutes can cause death of the gas concentration in a toxicity index is determined, then the PVC toxicity index 15.01, Halogen-free polyolefin toxicity index of 0.79. Smoke in PVC can only survive for 2 minutes, and replaced with halogen-free material, in which the survival of the smoke can be extended to 40 minutes, and greatly increased the time of a fire escape. Also, according to the material that the combustion flame retardant PVC cable smoke emitted light transmittance of 15% or less, that is, people smoke at this concentration, with their naked eye sight is about 2m. So in the fire, intense smoke filled the victim disoriented and Bianbu Qing direction, to extend the residence time in the fire, smoke and toxic gases causing further inhalation and suffocation. 
   Found that a large number of trials polyolefin base material, hydrated metal compound Al (OH) 3 or Mg (OH) 3 as flame combustion of materials of the gas released when the smoke density and the amount of halogen acid gas evolution can be achieved IEC standard requirements. Al (OH) 3 or Mg (OH) 2 is an inorganic hydroxide, which has excellent flame resistance, but also has low toxicity and smoke suppression, low corrosion characteristics, smoke suppression good, because smoke suppression and resistance burning equally important. 
   Developed countries have been very seriously LSZH wire and cable and related materials research and development and promotion of use, especially in high-rise buildings, subways, railway stations, airports, power stations and shopping malls and other relatively closed or officers to concentrate on the important buildings and facilities. In recent years, the developed countries but also in electrical and electronic equipment, restriction of lead, cadmium and other heavy metals and polybrominated biphenyls (PBB), polybrominated diphenyl ethers (PBDE) and other bromides are used, developed electronics industry giants have developed a its own "Green Plan", thus prohibiting or restricting the use of human and environmental harmful heavy metals and halogens, and done a lot of research and development, has launched many series of "green" electrical and electronic wire and cable. Some countries, such as Switzerland, Germany, strongly opposed the application of PVC, and has formulated strict laws and restrictions and eventual elimination of PVC applications. 
   Our LSZH wire and cable and related materials, the development and use lag developed about a decade. Until 2000 only after turning away from the situation entirely dependent on imports. Now made ​​LSZH wire and cable and related materials performance has been in line with national and international standards, but people also need to enhance awareness of environmental protection and safety, products also need to promote. 
This article is from China Wire & Cable Network
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