What are the main technical characteristics of low smoke halogen free flame retardant cables and fire resistant cables?

I. Low-smoke halogen-free flame retardant cables and fire-resistant cables of the main technical characteristics of how? 1. Smoke density polymer materials will produce more or less smoke when burning. Smoke is a combination of water vapor and gas and due to the non-combustion of the solid or liquid suspension formed into a mixture. Cable burning smoke density with Ds (a given moment than the optical density) and Dm to assess, it is in the test conditions, with the help of optical methods, to measure the smoke accumulation due to the beam attenuation, Dm that the total accumulation of smoke. the larger the Dm that the greater the amount of smoke during combustion, and vice versa. When cables are burned in a fire, the PVC material generally releases a very concentrated and opaque smoke during combustion. The reason for this is that the chlorine contained in the PVC smoke reacts with the antimony in the additives during combustion, resulting in incombustibility and the formation of antimony trichloride gas (which greatly dilutes the oxygen content of the air, thus suffocating people in a fire), as well as the release of black smoke molecules (carbon molecules) that impede the propagation of light. The above problems no longer exist in halogen-free cables.2. Toxicity and CorrosivenessOrdinary PVC cables release hydrogen chloride gas from the combination of chlorine and hydrogen in them when they burn. When the cable is required not to produce excessive smoke and toxic substances, or at elevated temperatures will not enhance its toxicity, PVC cable will be prohibited. Halogen-free cable using halogen-free polyolefin as the base material, it does not produce acidic gases in the combustion, so its toxicity and corrosiveness is much lower than ordinary PVC cable. 3. flame retardant due to PVC and other halogen-containing materials made of cables, although there are fire-retardant properties, but because of the amount of smoke and the production of toxic and corrosive gases, in the modern society and the requirements of the situation is increasingly high, halogen-free flame-retardant cables In modern society, halogen-free flame retardant cables have become the inevitable choice. In the halogen-free flame retardant, the role of flame retardant is mainly a large number of filled aluminum or magnesium hydroxide and other flame retardant fillers. This kind of material can release crystalline water when the cable is burned, absorb a lot of heat, thus inhibiting the polymer temperature rise, slowing down the thermal decomposition and reducing the burning speed. In addition, the water vapor produced by dehydration decomposition can dilute the flammable gas, thus providing a flame retardant effect. Of course, excessive addition of combustible materials in the organic material will reduce the mechanical and electrical properties of the material. Therefore, how to make halogen-free materials not only has excellent flame retardant properties, but also has good mechanical and electrical properties once became a difficult problem. 4. fire characteristics when the cable line in the fire can continue to play a role, and when the cable is inevitably required to be set up in high-risk areas of the line, the cable has a fire-resistant performance. IEC331 standard, fire-resistant cable can be 750 ℃ environment. The IEC 331 standard specifies that fire-resistant cables can be operated at 750°C for 90 minutes. When PVC cables burn, corrosive and ionizing gases are released that destroy the mica seal, creating an environmentally oriented environment. The halogen-free fire-resistant cables produced by a few world cable manufacturers using halogen-free flame-retardant materials and advanced fire-resistant structures do not have this problem and can be operated continuously for 3 hours at 1000°C. The IEC331 standard specifies that PVC cables can operate at 750°C for 90 minutes.

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