Introduction of polypropylene flame retardants

Describes the polypropylene (PP) flame retardant type and mechanism of resistance ene agent PP summarized research progress and trends. Efficient, low toxicity ,
Low smoke , low cost, versatile, new composite "green" flame retardant PP 21st century focus of the study .
Polypropylene (PP) is a hydrocarbon material , heat of combustion , it is not entirely produced by burning smoke PVC lubricant  and toxic gases, its application is limited . In order to improve flame retardant PP , broadening its field of application , you must add flame retardants.
A , PP fire retardant classification
PP flame retardant more categories, according to the basic performance is divided into inorganic and organic flame retardants ; according to high and low molecular weight divided into low molecular weight and high molecular weight flame retardant ; divided by use of additive flame retardant and reactive flame retardant . Which , by the use of method of classification is more commonly used classification methods . Flame retardant is added to the polymer during processing with a flame retardant
Liquid or solid , including phosphate, halogenated hydrocarbons , the advantage of easy to use for a wide range ; those containing reactive flame retardant is Cl,, Br, P and other elements and reactive flame retardant class of compounds , they are copolymerized with the resin to give a resin flame retardant. Two , PP flame approaches, methods and mechanisms
( A ) , flame retardant PP pathway mainly through three kinds of ways to achieve [ 1 ] : ( 1 ) using the additive flame retardant , flame retardant added over mechanical mixing the polymer to achieve flame purpose ; ( 2 ) use of reactive flame retardant, a flame retardant as a reactive monomer that participate in the reaction ,
Grafted to the polymer main chain or side  chain , the modified polymer has a flame retardant ; ( 3 ) a flame retardant polymer itself . (B ) , the basic method of flame retardant PP basic methods include: ( 1 ) use of foam or non- foam refractory material coating the surface of PP material , to
With oxygen or thermal isolation ; ( 2 ) through the modification of the modified PP matrix material flame retardant. The second method is the main method . ( Three ) , flame retardant mechanism
1 . Termination of a chain reaction mechanism
PP combustion , the general decomposition  Sodium stearate of hydrocarbons. Further oxidation of hydrocarbons at high temperatures, decomposition of free radical HO •. HO • The chain reaction
Makes the flame should continue . Halide decomposition of hydrogen halide (HX). HX can capture high-energy HO • and produce X • and
H 2O, while X • R • reacts with the polymer and the HX, but also capture the HO •. This cycle enables highly active HO • Less
Less will eventually contribute to the ripple cut HO • terminate hydrocarbon combustion flame to achieve the purpose . For PP, halides
Usually without the use of fluoride chloride or bromide or iodide . Because fluoride too lively , the formation of molecular fluorine and very stable
Iodine forming compound is unstable , it is rarely used.
2 . Mechanism of protective film
Flame temperature in the combustion swells into a layer of non-combustible protective film covering the surface of the material , isolated from the air and fire retardant . In
Phosphate flame retardant in the PP phosphate, halogen hydrocarbon ester. They differentiate to form a layer of porous insulating film coke , separated
Absolutely air to prevent heat transfer , and thus play a role in flame .
3 . Cooling mechanism
Flame retardant polymer surface can  PVC heat stabilizer for window melt at a lower temperature , the latent heat absorbed or endothermic reaction , consume a lot of heat , from
And to prevent burning. Such as Al (OH) 3 can play in PP flame retardant effect. It is a non- flame-retardant filling aids . When the temperature
No more than 200 ℃, hydration molecules and Al (OH) 3 combined with very strong, even at 230 ℃ for continuous heating will not significantly decompose.
When the polymer is exposed to heat , one of the Al (OH) 3 hydrated plays the role of heat . When the temperature is higher than 250 ℃, the polymer combustion,
Al (OH) 3 decomposes to absorb a lot of heat , and  Glycerol monostearate generate water . Water vapor , and absorb a large amount of heat , thereby reducing the polymer
Temperature of PP pyrolysis gas combustion products, the speed is very slow , less than the concentration of combustion can be maintained , thereby preventing burning.