Discuss the characteristics of environmentally friendly wire and cable

Hazardous substance content requirements. At present, the so-called common environmentally-friendly wire and cable refers to cables containing lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers within the limits of the EU RoHS. And the wire and cable must not contain environmental hormones, and should not pollute the soil and water. Flame-retardant properties, environmentally-friendly flame-retardant wire and cable have good flame-retardant properties. When exposed to flames and fire sources, they can prevent the flame from spreading and spreading rapidly, and control it in a limited area to minimize losses. High-grade environmentally-friendly flame-retardant wire: Refers to the halogen-free environmentally-friendly flame-retardant wire, which not only meets the requirements of ordinary environmentally-friendly flame-retardant wires, but also contains no halogen, and does not generate harmful gases and corrosive gases after combustion. According to the requirements of environmental protection, the flame-retardant wire ensures that the gas released during combustion has low smoke characteristics, no halogen and low toxicity without reducing the flame retardant grade. In the event of fire, in order to ensure that all personnel have escape opportunities, the visible distance shall not be less than 15m, and the visible distance of some environmentally friendly wire and cable when burning smoke may reach 97m, while the general cable is only 5~8m. The cable insulation is usually fired, and the high-grade environmentally friendly wire emits white smoke, mainly water vapor, and emits a small amount of smoke.

 The temperature resistance level is increased and the current carrying capacity is increased. Generally, the ordinary PVC wire has a temperature resistance rating of 70 ° C, while the environmental protection wire has a temperature resistance of 105 ° C, 125 ° C, and 150 ° C, which is 30 ° C to 60 ° C higher than that of an ordinary cable. After the relevant tests, the environmentally-friendly conductors of the same specification cross-section can be increased by 30% to 50% than the ordinary conductors, and the cross-linking degree can be increased to 80% or more. Halogen-free environmentally-friendly wires are usually cross-linked products. In recent years, the wire and cable industry has generally adopted the process of irradiation cross-linking. The molecular structure of polyolefin-based materials has been changed from the original nuclear technology through high-energy electron irradiation processing. The linear structure is transformed into a mesh structure. This process can improve the operating temperature of the cable and the ability to resist transient high current carrying capacity during short circuit, and greatly improve the temperature resistance level. Although the cost of high-grade environmentally-friendly flame-retardant wires has increased, considering the increase in current-carrying capacity, high-grade environmentally-friendly wires are more cost-effective, that is to say, the same current-carrying capacity, higher cost of environmentally-friendly flame-retardant wires.

So, what is the current status of environmentally friendly wire and cable?

In the 1980s, the development of low-smoke and halogen-free flame-retardant wire and cable began. The advantage of this material is that it is low-smoke, non-toxic, and produces metal oxides and water vapor when burned by open flame. The low-smoke, halogen-free flame-retardant polyolefin is based on a halogen-free polyolefin, and a large amount of magnesium hydroxide or aluminum hydroxide activated by EVA (ethylene-vinyl acetate copolymer) is kneaded in a polyethylene matrix to utilize hydrogen hydroxide. When the material is burned and heated, it is decomposed into metal oxides and water to achieve the purpose of flame retardant. Its reaction formula is as follows:

Mg(OH)2→MgO+H2O endotherm

2Al(OH)3→Al2O3+3H2O endotherm

The low-smoke, halogen-free flame-retardant polyolefin is flame-retardant by means of heat absorption and metal oxide oxygen barrier. The flame retardant mechanism is as follows: First, when the wire and cable are burned, the surface hydroxide is decomposed, and the reaction is endothermic. The reaction absorbs a large amount of heat in the surrounding air and reduces the temperature of the surface of the wire and cable. Second, the generated water molecules absorb a large amount of heat on the surface of the wire and cable, and the water vapor also isolates the oxygen. The third is the metal oxide produced. Crusts prevent another contact between oxygen and organic matter.

Developed countries have developed halogen-free and low-smoke cables in the 1980s, and strongly recommend the use of such harmless wire and cable to replace and gradually abandon the use of toxic PVC wire and cable. That is to say, the toxicity of the halogen-containing cable released in the fire is very terrible. If the toxicity index of the gas concentration that can cause death in 30 minutes is judged as 1, then the toxicity index of PVC is 15.01, no halogen. The toxicity index of polyolefin is 0.79. People can only survive for 2 minutes in the smoke of PVC, and replaced with halogen-free materials, the survival of people in their smoke can be extended to 40 minutes, greatly increasing the escape time in the fire. In addition, according to the relevant materials, the light transmittance of the smoke emitted by the flame-retardant PVC cable is less than 15%, that is, the person is in this concentration of smoke, and the naked-eye line-of-sight is about 2 m. Therefore, in the fire, the strong diffuse smoke made the victim dizzy and could not distinguish the direction, prolonging the time spent in the fire, resulting in further inhalation of smoke and toxic gases and suffocation.

In a large number of experiments, it was found that the smoke density and halogen acid gas volatilization of the gas released by burning the material based on polyolefin and hydrated metal compound Al(OH)3 or Mg(OH)3 as flame retardant can reach Requirements of the IEC standard. Al(OH)3 or Mg(OH)2 is an inorganic hydroxide which has excellent flame retardancy, low toxicity, smoke suppression and low corrosion. It has good smoke suppression because of smoke suppression and resistance. Burning is equally important.

Developed countries have always attached great importance to the development and promotion of low-smoke, halogen-free flame-retardant wire and cable and related materials, especially in important buildings and facilities where relatively high-rise buildings, subways, stations, airports, power stations and shopping malls are relatively closed or concentrated. In recent years, developed countries have restricted the use of heavy metals such as lead and cadmium and polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE) in electrical and electronic equipment. The electronics and electrical giants in developed countries have developed Their respective "green plans" have banned or restricted the use of heavy metals and halogens that are harmful to humans and the environment, and have carried out extensive research and development work, and many series of "green" wire and cable for electronic appliances have been introduced. Some countries, such as Switzerland and Germany, strongly oppose the use of PVC and have enacted strict laws that limit and will eventually eliminate the use of PVC.

The development and use of low-smoke and halogen-free flame-retardant wire and cable and related materials in China have lagged behind in developed countries for about ten years. It was not until 2000 that it gradually got rid of the situation of total dependence on imports. At present, the performance of domestic low-smoke halogen-free flame-retardant wire and cable and related materials has met the relevant national and international standards, but people's awareness of environmental protection needs to be improved, and products need to be vigorously promoted.