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P: 2009-03-05 12:34:16
P: 2009-03-05 13:17:57
Halogen containing materials, will happen because of the heat decomposition, releases hydrogen halide, hydrogen halide to capture the activity of free radicals HO, so that it can slow down and termination of chain combustion oxidation reaction to reach the purpose of fire-retardant. In addition halogenated flame retardant are precursors of hydrogen gas, which is heavier than air, the proportion can be scheduled on behalf of the air, the formation of protective layer, isolated from the role of oxygen, thus delaying or burning off, the chlorine content of PVC resin reached 56.8 % resin oxygen index is as high as 42, the Flame of its own on the better for the self-extinguishing polymer.
Halogen-free flame retardant polyolefin material is selected as the basis of polyolefin polymers, its oxygen index for the base material 18, as the combustible, add a large number of Al (OH) 3 or Mg (OH) 2 formed. Department of pure polyolefin hydrocarbons, easily burning, burning when broken down into water and carbon dioxide, does not produce obvious toxic smoke and corrosive gases. Al (OH) 3 or Mg (OH) 2 after heating to release crystal water, absorb substantial heat, thus inhibiting polymer temperature rise, retard thermal decomposition, to prevent burning. In addition, the dehydration produced by decomposition of water vapor can also dilute the flammable gases, which play a fire-retardant effect.
［cuijiude 在 2009-3-5 13:18:28 编辑过］
P: 2009-03-06 14:51:07
The flame retardant mechanism of halogen ang halogen-free is different(Black as the polyvinyl chloride containing halogen, blue is the halogen-free polyolefin)
Because of the materials containing halogen will decompose , release hydrogen halide,and halogenating hydrogen can capture the activity of free radicals HO when heated.Thus can slow down and terminate the oxidation reaction of combustion chains to achieve the purpose of flame retardant.Besides the gaseous halogenating hydrogen is Flame retardant gas ,and it's heavier than air so that it is able to exhaust and replace the air and form protective layer which can isolated from the oxygen.Thus burning delay or extinguished.The chlorine that PVC resin content reached 56.8 % ,and the resin oxygen index is as high as 42.
It is the self-extinguishing polymer for the flame retardant itself is good .
Halogen-free flame retardant polyolefin materials choise the polymers based on polyolefin. Its oxygen index for the base material which is combustible and add a large number of Al (OH) 3 or Mg (OH) 2 reach to 18. Polyolefin is pure hydrocarbons can be easily burning.They decompose into water and carbon dioxide, no obvious smoke and poisonous corrosive gas when burning.Al (OH) 3 or Mg (OH) 2 release crystal water and absorb substantial heat after heating .Thus restrain polymer temperature rise, retard pyrolysis, and prevent burning. In addition, the water vapor produced by dehydration decomposition can also dilute the flammable gases, which play the effect of flame retardant .
［抗倭先锋 在 2009-3-6 14:53:21 编辑过］
P: 2009-03-21 12:55:21
Although both halogen and halogen-free materials can be fire retardant, the mechanisms are different. (PVC with halogen content is black in color while halogen-free Polyolefin is blue)
The material containing Halogen can release Hydrogen Halide when heated. Hydrogen Halide absorbs free HO, which slows down or even terminates the chain reaction of oxidation (combustion). In addition, since Hydrogen Halide is non-flammable and heavier than air, it stays below the air and isolates the oxygen from the burning object when released. Thus the fire is confined and then extinguished. In the particular case of PVC resin, the high Chlorine content (52.8%) and oxygen index (42) also contribute to its superior non-flammable property. It is so called self-extinguishable polymer material.
On the other hand, halogen-free material comprises of base material Polyolefin and a large amount of Al(OH)3 or Mg(OH)2. Polyolefin itself is pure hydro-carbon with oxygen index of 18. It is extremely flammable and decomposes into water and CO2 when burnt, without producing visible smog or corrosive poisonous gas. Al(OH)3 or Mg(OH)2 releases water vapors as well when its crystalline framework destructed by heat. However, the vaporization of the water then absorbs significant amount of heat so that effectively stopped further material destruction and therefore extinguish the fire. Besides, water vapor itself dilutes the flammable gas and further enhances the fire retardant effect.
P: 2009-05-29 10:50:36