Chemical Industry: Application of Flame Retardants in Plastics

(1) Polyolefin Polyolefin burns easily. The upper end of the flame is yellow and the lower end is blue. It melts and drips when burning, so it requires a certain amount of flame retardant. Larger, more commonly used are halogenated hydrocarbons and oxidized paraffin. The effect of using oxidized hydrocarbons alone is poor and will affect the transparency of the plastic. The most representative halogenated hydrocarbons are chlorinated paraffins. In addition, there are also chlorinated paraffins. Polyethylene, tetrabromoethane, tetrabromobisphenol A, etc. Chlorinated paraffin will decompose and cause coloring at 200°C, and cannot be used for high-temperature molding resins (such as polypropylene). Flame retardants with high halogen content, such as aromatic bromide and perchloropentane, have good heat resistance. In addition, halogen-containing phosphate esters are also suitable for polyesters.

(2) Polystyrene and ABS resin Polystyrene is easy to burn and will continue to burn after being removed from the fire. The flame will be yellow and emitting. Black smoke softens when burning, and halogen-containing phosphates and organic bromides are generally used as flame retardants. Halogen-containing phosphate esters have good compatibility, while the dosage of aromatic pyridines such as tetrabromobisphenol A is slightly larger, and products with good transparency and weather resistance can be produced. The ones with higher flame retardant effects are aliphatic and alicyclic compounds. Bromide and hexabromocyclododecane are widely used as flame retardants for polystyrene.

ABSThe resin is propylenenitrile, butadiene Terpolymers of styrene and styrene can be made into various resins with different properties due to different proportions, and their flammability is also different, but the flame retardant method is similar to that of polyethylene. Considering thatABSthe resin molding temperature is generally 200-260C,So high temperature resistant flame retardants must be used, such as perchlorocyclodecane, hexadecane /span>BromeBenzene, etc.

(3) Polyester Polyester resin is easy to burn, with a yellow flame and black smoke. Reactive flame retardants are generally used, such as tetrabromophthalic anhydride. Chlorinated anhydride is also commonly used, but its light resistance is poor and it easily turns yellow under sunlight. It is often used together with ultraviolet absorbers. Aluminum hydroxide is the most important additive flame retardant for unsaturated polyester. Some additive flame retardants, such as halogen-containing phosphate esters, soften the resin, thus limiting their application.

(4) Polyvinyl chloride Polyvinyl chloride contains halogen atoms in its molecules and is flame retardant. When the flame is extinguished, the flame will be yellow, and the lower end will be green and white smoke. When burning, the plastic becomes soft and emits a pungent smell. In practical applications, due to the large amount of organic ester (such as DOP) flammable plasticizers used in PVC, it must Considering the issue of flame retardancy,

The use of carbon dioxide alone in PVC resin has flame retardancy, and the added amount is 1% ~3%. If used together with chlorinated paraffin, the flame retardancy will be better. Transparent PVC products should use phosphate ester flame retardants. Tricresyl phosphate (TCP) is commonly used, but TCP has poor low-temperature performance, and halogen-containing phosphate esters have good flame retardant effects. , does not affect the physical properties of plastics, and the dosage is smaller, but the price is slightly more expensive.