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. UL94 is a plastic 

flammability standard issued by Underwriters Laboratories. This standard classifications

 plastics according to the burning of plastics with different thickness. From the

 lowest (minimum flame retardancy) to the highest (maximum flame retardancy) 

lassification: HB: is slowly burning on a sample placed horizontally, burning less than

 76 mm/min for a material with a thickness less than 3mm; V2: stops burning 

within 30 seconds of the vertically placed sample, allowing droplets to be dripped 

down; V1: in vertical samples Stop burning for 30 seconds and allow to drop non

burning particles; V0: stops burning in 10 seconds on the vertically placed sample 

and allows to drop non burning particles; 5VB: stops burning in 60 seconds on the 

vertically placed sample, not allowed to drop, allowing holes to appear on the s

ample; 5VA: stops in a vertical sample of 60 seconds. Stop burning, do not allow

 dripping, and do not allow holes in samples. It can be seen that flame retardancy

 V0 > V1 > V2. The so-called V1, V2 flame retardant is not appropriate, after all, 

s determined by the UL94 standard, ABS is usually added four bromo bisphenol 

-A (TBBPA) as flame retardant.