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Why ABS and V0 flame retardants are easy to carbonization?

Flame-retardant ABS is made from YISHION ABS resin, with high thermal stability,

 flame retardants and so on. The preparation methods of flame retardant ABS are

 usually divided into two types. One is copolymerization of monomers containing

 halogen elements in graft polymerization, and then the flame retardant ABS is 

prepared. This method is difficult to achieve satisfactory flame retardancy because 

of the limitation of the amount of fourth monomers during copolymerization. The

 two is to blend the compounds or polymers containing halogen elements and other

 flame retardant additives and ABS resin to make blends of flame retardant ABS, 

which has been widely used in industrial production. The flame retardant is easily 

decomposed, carbonized or yellowing at high temperature, so the forming temperature 

should be as low as possible. It is usually set below 190 C (the resin melt temperature

 is below 220 C). "Carbonization" is not bad, the flame retardancy principle can be

 divided into four mechanisms: (1) isolation of oxygen and promoting polymer 

carbonization to reduce flammable gas production and flame retardancy; (2) produce

 non flammable gases to dilute oxygen concentration to slow combustion speed; (3)

 heat absorption and release of water gas before the combustion occurs, The flame 

retardant effect is achieved by lowering the temperature; (4) interfering with the 

formation of free radicals by chemical means. According to the composition, the 

addition type flame retardants mainly include inorganic flame retardant, halogen 

flame retardant (organic chloride and organic bromide), phosphorus flame retardant,

 and phosphorous compound is a promising combustible in the global halogen free 

combustible agent. Organic phosphate, such as BDP and RDP, is the main phosphorus

 burning inhibitor in China. The refractory carbonization layer (char) is formed on the

 plastic surface after the plastics are heated, and the carbonized layer obstruct the

 flow of the combustible gas and the heat radiation produced by the combustion to

 achieve the purpose of flame retardancy. Since oxygen molecules are beneficial to 

the formation of carbonized layers, such flame retardants are especially suitable for 

oxygenated resin materials such as PET. On the one hand, the formation of carbonized

 layer can prevent further pyrolysis of polymer, and on the other hand, it can prevent

 its internal thermal decomposition producing organisms into the gas phase and

 participate in the combustion process.


HB: burns slowly on the horizontal set of samples, and the combustion speed

 is less than 76 mm/min for the material less than 3mm; V2: stops burning within

 30 seconds on the vertically placed sample and allows droplets to be dripped 

down; V1: stops burning in 30 seconds on the vertically placed sample and 

allows droplets to be dripped without burning; V0: is vertical. The placed sample 

stopped burning for 10 seconds and allowed to drop the non burning particles; 

5VB: stopped burning in 60 seconds on the vertically placed sample and allowed

 holes to appear on the sample; 5VA: stopped burning in 60 seconds on the 

vertically placed sample, not allowed to drop, and no holes were allowed to

 appear on the sample. It can be seen that flame retardancy V0 > V1 > V2.

 The so-called V1, V2 flame retardant is not appropriate, after all, is determined

 by the UL94 standard, ABS is usually added four bromo bisphenol -A (TBBPA)

 as flame retardant.

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