Flame retardant wire and cable can be divided into general flame retardant wire and cable, low smoke and low halogen flame retardant wire and cable and low smoke halogen flame retardant wire and cable. At present, China's low smoke halogen free flame retardant wire and cable materials mainly rely on imports, expensive, application is limited to a certain extent. With the rapid development of China's economic construction and the improvement of safety performance requirements, there is a growing demand for low-smoke halogen free flame retardant wire and cable. Many domestic manufacturers have increased efforts to develop low-smoke halogen free flame retardant wire and cable materials. In 2002, the ministry of public security issued a mandatory standard GA306-2001 of the flame retardant and fireproof cables, plastic insulated flame-retardant and fire-resistant cable classification and requirements, and has carried on the classification to fireproof cables, and the smoke of fire-resistant cable and made specific provision smoke toxicity to further improve the flame retardant and fireproof cable standard system in our country, the promotion and application of flame retardant, high efficient and pollution-free flame retardant, fire-resistant cable plays a promoting role. Since 2000, China's cable materials in short supply, some products even out of stock. China's existing wire and cable production enterprises nearly 5000. Because urban and rural power grid reformation, the development of the western region, the three Jia engineering and communications facilities large upgraded the huge demand for wire and cable products. So, from the point of a period of time, cable materials in our country has broad market prospects for development. In the early 1980s, low smoke halogen-free flame retardant cable materials have been developed abroad. By the late 1980s, a second generation of halogen-free flame-retardant plastics for wire and cable had been developed. Compared with the first generation of products, the second generation of halogen-free flame-retardant plastics has improved in flame retardant performance, smoke generation, toxicity, corrosion performance, mechanical performance, electrical performance, and its high-speed extrusion performance is a major feature.

Japan issues more than 50 patents related to halogen-free flame retardant cable materials every year. Most of the patents belong to Hitachi electric, union carbide and other companies such as fujiura, sumitomo and ohtani. This kind of patent attempts to solve the central problem of halogen-free flame retardant cable materials by different methods, that is, to overcome the contradiction between flame retardant properties and other properties, and to balance all kinds of properties comprehensively; There are also many patents devoted to the development of new coordination agents, among which magnesium hydroxide is a very important coordination agent, which has been patented in many countries. Low smoke halogen free flame retardant wire and cable material is the key development direction of flame retardant wire and cable in the future.

At present, China's flame retardant wire and cable products are mainly halogen-containing flame retardant, which releases a large amount of smoke and corrosive halides when burning, causing casualties and corrosion of various equipment, namely the so-called "secondary disaster". In order to achieve the purpose of low smoke, low toxicity and flame retardant, many domestic and foreign manufacturers are committed to the development of low smoke, low halogen, low smoke halogen free flame retardant materials. When this kind of material burns, smoke quantity is little, release poisonous gas little, reduce the harm to human body and instrument equipment. The research on low smoke, low halogen and low smoke halogen free flame retardant wire and cable materials in developed countries is relatively early and the technology is mature. The research and development of low smoke and low halogen, especially low smoke halogen free flame retardant wire and cable materials in China is relatively late. At present, the research on low smoke halogen free flame retardant wire and cable materials in China is still in the early stage. Some manufacturers have produced low smoke halogen free flame retardant wire and cable materials, but most of them have poor mechanical properties and processing properties.

1. Low technical level

The technical level of our country's wire and cable material has been a big gap with foreign countries. In the early 1980s, many manufacturers in China's cable industry successfully developed general flame-retardant cables. According to statistics, more than 40 kinds of flame retardant cables have been trial-produced from 1987 to 1991, basically using flame retardant PVC and flame retardant neoprene. This kind of flame retardant cable is only suitable for the occasions with low flame retardant requirements, and for some special occasions with high flame retardant requirements, it is required to use low smoke, halogen free flame retardant cables, such as: Underground utilities, high-rise building, ships, warships, etc., due to low technology in our country, resulted in the low production capacity, the vast majority rely on imported from abroad to meet demand, and by foreign technology monopoly, low smoke zero halogen flame retardant cable material price is very high, in 25000 yuan/ton - 35000 yuan/tons, paid a high price in China.

2. Limited application fields

Low smoke zero halogen flame retardant cable materials because of its environmental protection conform to the requirements of society, is the development direction of cable materials in our country, but so far our country's low smoke zero halogen flame retardant cable materials application field is very limited, is mainly used in the subway in big cities, urban rail, ship, high building and plant and other fields, in Beijing, Shanghai, guangzhou, xi 'an, shandong and other developed provinces and cities, in many remote places rarely used, is far from universal.

3. Broad prospects

As "environmental protection cable" - halogen-free flame retardant cable has broad market prospects.

China's domestic annual output of wire and cable accounts for about 20% of the world's output, accounting for about 15% of the world's total output of wire and cable, about 80 billion yuan (RMB), China has developed into the world's largest wire and cable market. With the development of the society, people on the environment problem more and more attention, many countries have developed all sorts of environmental policies, such as the eu ROHS directive: from July 1, 2006, in new on the market of electrical and electronic equipment, banning the use of lead, mercury, cadmium, hexavalent chromium, polybrominated diphenyl ethers (PBDE) and polybrominated biphenyl (PBB), and other harmful substances. Among them, PBDE and polypbb are mostly used as flame retardants for plastics. Japan's major electrical companies have also made corresponding requirements, from March 2006 in various electrical appliances used in the wire and cable halogen-free requirements. Therefore, halogen-free flame retardant wire and cable has become an important development direction of the industry. In China, with the increase of people's attention to the environment, halogen free flame retardant products are more and more widely used. For example, halogen free flame retardant wires and cables are in great demand in the home appliance industry, building materials, telecommunications, automobile and other industries. In terms of electrical appliances, China has become the world's largest producer of electrical appliances and the world's largest exporter of electrical appliances. Considering the disguised "technical barriers" caused by some countries' restrictions on the import of halogen-containing products, halogen-free flame-retardant wires and cables have a very large application prospect in the household appliance industry. Relevant regulations in China require high-rise buildings to adopt halogen-free flame-retardant wires and cables. In addition, halogen-free requirements are added on the basis of flame retardant in the wires used for telecom infrastructure equipment and automobile wires. To sum up, halogen-free is the development direction of flame retardant wires and cables at home and abroad, with a very broad market prospect and great market potential.

In our country, many enterprises have carried out the research and development of low smoke halogen free flame retardant cable material technology, promoting the development of low smoke halogen free flame retardant cable material market, has also made some achievements.

Beijing university of chemical industry in 2004 developed a high-performance halogen-free flame retardant cable materials technology, for the first time in the domestic low filled with red LinXie effect using nanometer magnesium hydroxide flame retardant in the new method and two different surface treatment status of micron magnesium hydroxide with technology, make the material has high strength, high flame retardant, good liquidity, good heat resistance, excellent comprehensive performance, performance reached the international advanced level of similar products, breaking the monopoly imports passive situation of the domestic market.

The halogen-free flame retardant cable material successfully developed by Beijing university of chemical technology can be comparable with imported products in performance, but the price is lower than imported products, which can save the raw material cost of 3000-5000 yuan/ton for cable manufacturers, and has a strong market competitive advantage.

In recent years, with the development of flame retardant technology of cable materials, new flame retardant cables have been produced. In Europe, America, Japan and other countries, environment-friendly wire and cable has become the mainstream product of all cable varieties. The government strictly prohibits the use or import of non-environment-friendly cable. Ordinary contains a large number of halogen flame retardant materials, at the time of combustion will produce a lot of smoke and poisonous corrosive halolide gases, and halogen-free flame retardant main choice in polyolefin, so low smoke zero halogen cable after will be the main trend of development, from the following aspects of low smoke zero halogen cable material extrusion were discussed.

1. Extrusion equipment

(1) the main component of wire and cable extrusion equipment is screw rod, which is related to the application range and production efficiency of the extruder. In order to meet the needs of different plastic processing, there are many types of screw rod. Low smoke halogen-free flame retardant cable material contains high filling of magnesium hydroxide or aluminum hydroxide, so for the selection of screw generally choose the general type of screw and its compression ratio can not be too large, generally between 1:1 ~ 1:2.5 is more appropriate.

(2) in the extrusion process, there is another important factor affecting the low-smoke halogen free cable material extrusion, that is, the cooling device of the extruder. Due to the particularity of low-smoke halogen free material, large heat is generated due to friction in the extrusion process, which requires the extruder to have a good cooling device in order to control the process temperature. This is a problem that cannot be ignored. If the temperature is too high, the surface of the cable will have large air holes. If the temperature is too low, the current of the whole machine will increase, which is easy to damage the equipment.

2. Extrusion die

Due to the high filling material of low-smoke halogen free cable material, the strength, tensile ratio and viscosity of the melt are quite different from other cable materials in the molten state, so the selection of the mold is also different. The first is the choice of extrusion mode of the mold. For the extrusion of low-smoke halogen free cable materials, the extrusion mold of insulation should be extruded by extrusion type, and the semi-extrusion type should be selected in the process of sheath extrusion, so as to fully ensure the tensile strength, elongation and surface finish of the material. The second is the choice of mold sleeve, the use of extrusion mold, because the viscosity of the material is large, so that the pressure of the head is very big, when the extrusion out of the mold will be expanded, so the mold sleeve should be smaller than the actual size. Finally no ordinary on the mechanical properties of the low smoke zero halogen cable materials and low smoke low halogen material is superior, the draw ratio is small, only about 2.5 ~ 3.2, so in when choosing mould also should fully consider its tensile properties, which requires the die set equipped with not too much, otherwise the surface of the cable is not dense, and crowded package is loose.

At present, there is still a big gap between the technology of low-smoke halogen free flame retardant cable materials in China and that of foreign countries. The government of our country needs to invest heavily in policies, funds and other aspects, research and development, study and introduce foreign advanced technology, and promote the rapid development of low-smoke halogen free flame retardant cable materials technology in China.