Flame retardant principle, the main types of flame retardant

September 3, 2022 Longchang Chemical

Flame retardant principle, the main types of flame retardant

Flame retardants are used to improve the flame-resistance of molecular materials by increasing the ignition point of molecular materials or reducing the burning speed of materials, thus increasing the rescue time, saving lives and reducing losses. According to the structure, flame retardants can be divided into macromolecular polymeric and small molecule type flame retardants; according to the use method, they can be divided into additive flame retardants and reactive flame retardants; according to whether the material contains halogen, they can be divided into halogen flame retardants and non-halogen flame retardants. Additive flame retardants are mostly used in thermoplastic polymers, which do not react chemically with other components in the material and only exist in the polymer material in a physical way; reactive flame retardants are mostly used in thermosetting polymers, which participate in the chemical reaction of synthetic polymers and become the structural unit of polymers.

According to the three main elements of combustion – combustible material, combustible material and fire source, flame retardants flame retardant principle can be summarized as the following four.

First, through the absorption of heat to achieve flame retardant. Such as inorganic flame retardant aluminum hydroxide decomposition at high temperatures, the release of crystalline water, crystalline water evaporates into water vapor. This process will absorb a lot of heat, reduce the temperature of the material surface, flame retardant.

Second, by generating non-flammable gas dilute oxygen and slow down the rate of combustion. Such as aluminum hydroxide flame retardant produces water vapor can reduce the concentration of oxygen around the material and inhibit the spread of fire.

Third, the formation of a dense cover layer on the surface of the material, isolating the material from oxygen contact. Such as phosphorus flame retardants in high temperature conditions will become more stable structure of cross-linked solid material or carbonized layer wrapped around the material to prevent continued combustion.

Fourth, capture the free radicals involved in the combustion reaction, inhibit the free radical chain reaction. Such as bromine flame retardants in high temperature conditions, polymer materials by thermal decomposition, bromine flame retardants and thermal decomposition products at the same time into the gas phase combustion area, capture the free radicals in the gas phase combustion area, inhibit the free radical chain reaction, thereby preventing flame propagation.

According to the broad categories, flame retardants can be divided into halogen-containing flame retardants and non-halogen flame retardants. The biggest difference between the two is that the former contains halogens, while the latter does not contain halogens. However, halogen-free is not absolutely free of halogen, but is defined according to the amount of its content. Halogen-free is defined as less than 900ppm of bromine and chlorine, and less than 1500ppm of total bromine and chlorine. halogenated flame retardants mainly refer to brominated flame retardants and chlorinated flame retardants, of which, brominated flame retardants are the most used and widely used flame retardants. Most flame retardant materials contain halogens. Halogenated flame retardants have the characteristics of low addition, significant flame retardant effect and low price. In the addition of flame retardants, halogen elements have good compatibility with polymer materials and do not affect the physical and chemical properties of the materials themselves. But at the same time, we can not ignore the individual brominated flame retardants. Such as hexabromocyclododecane, in the combustion process will release a lot of smoke as well as toxic gases, to the fire, escape and recovery efforts to bring difficulties.

In the halogenated flame retardants face a lot of controversy, we need to understand the following facts.

First, brominated flame retardants are still widely used worldwide, and there are currently as many as 70 types of brominated flame retardants. The EU and many countries authorized list and candidate list only contains hexabromocyclododecane, including 2 to 3 kinds of halogenated flame retardants. The vast majority of brominated flame retardants have been rigorously evaluated to prove that they are harmless to humans and the environment, and some brominated flame retardants, such as tetrabromobisphenol A, are less toxic than table salt.

Second, under the correct operating conditions, the use and recycling process of brominated flame retardants will not produce new hazardous gases to the outside world, and the recyclability is better than other flame retardant systems. Bromine flame retardants have a wide range of applicability, almost all the materials need to be flame retardant.

Halogen-free flame retardants include phosphorus-based flame retardants, intumescent flame retardants, inorganic flame retardants, silicon-containing flame retardants and bio-based flame retardants. There are many kinds of halogen-free flame retardants, but they face a common problem, that is, it is difficult to achieve a good flame retardant effect, and there is an impact on the mechanics of the material and processing properties. Therefore, halogenated flame retardants and non-halogen flame retardants have their own advantages and disadvantages, people should take into account the structure of the substrate being flame retarded, the use of the environment and recycling, etc. when choosing flame retardants. Most of the halogen-free flame retardants contain the elements of phosphorus and nitrogen.

I. Phosphorus flame retardants. Phosphorus flame retardants are divided into inorganic phosphorus flame retardants and organic phosphorus flame retardants, phosphorus flame retardant modification and compounding flame retardant is the focus of its work. Phosphorus flame retardants mainly work in the initial stage of decomposition of the material in the fire, forming a protective film, isolated from the outside heat and air.

Second, the expansion of flame retardants. Intumescent flame retardants can effectively protect the material exposed to the flame for a long time.

Third, inorganic flame retardants. Inorganic flame retardants have good thermal stability, flame retardant, non-volatile, non-corrosive gas, small smoke generation, etc., and are the main raw materials of low-halogen halogen-free flame retardant system.

Fourth, silicon-containing flame retardants. Silicon containing flame retardants, Si-O-Si structure is stable, and has the characteristics of low toxicity, anti-drip, promote the formation of carbon and smoke suppression during combustion.

V. Bio-based flame retardants. Although bio-based flame retardants are only in the initial stage of research, they have gradually become a hot spot of attention and research based on their advantages of low price, non-toxicity and wide range of resources.

Scientific understanding of the environmental protection of flame retardants. In recent years, halogen-free flame retardants are increasingly sought after. For a long time and even now, “halogen flame retardants are toxic and harmful, halogen-free flame retardants are environmentally friendly and are the future direction of flame retardants,” the wrong view is deeply rooted. Halogen-free flame retardants “halogen-free = environmental protection” viewpoint has become popular. In fact, according to the international common chemical classification and labeling system, among all the more than 70 kinds of commercial brominated flame retardants, only TBBA (tetrabromobisphenol A) and HBCD (hexabromocyclododecane) two products are clearly defined as toxic and harmful. And some non-halogen flame retardants such as the vast majority of phosphate esters and some phosphates and hypophosphates themselves carry the label of environmentally hazardous substances. Therefore, there is no scientific basis to judge whether it is environmentally friendly by containing certain chemical elements.


Flame retardant plasticizers of the same series

Synoflex® T-50 T-50; ASE CAS 91082-17-6
Synoflex® ATBC Acetyl tributyl citrate CAS 77-90-7
Synoflex® TBC Tributyl citrate CAS 77-94-1
Synoflex® TCPP TCPP flame retardant CAS 13674-84-5
Synoflex® DOTP Dioctyl terephthalate CAS 6422-86-2
Synoflex® DEP Diethyl phthalate CAS 84-66-2
Synoflex® TEC triethyl citrate CAS 77-93-0
Synoflex® DOA Dioctyl adipate CAS 123-79-5
Synoflex® DINP Diisononyl Phthalate CAS 28553-12-0/685 15-48-0
Synoflex® TMP Trimethylolpropane CAS 77-99-6
Synoflex® TEP Triethyl phosphate CAS 78-40-0
Synoflex® TOTM Trioctyl trimellitate CAS 3319-31-1
Synoflex® BBP Bio-based plasticizers, High-efficiency plasticizer
Synoflex® TMP Trimethylol propane CAS 77-99-6
Sinoflare® TCEP Tris(2-chloroethyl) phosphate CAS 115-96-8
Sinoflare® BDP Bisphenol-A bis(diphenyl phosphate) CAS 5945-33-5
Sinoflare® TPP Triphenyl phosphate CAS 115-86-6

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