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How much do you know about flame retardants? ----CR-504 flame retardant
编辑:Fujian Wynca Technology Co.,Ltd时间:2021-03-16

How much do you know about flame retardants?

Flame retardants, functional additives that endow flammable polymers with flame retardancy, are mainly designed for the flame retardancy of polymer materials; there are many types of flame retardants, which are divided into additive flame retardants and reactions according to the method of use Type flame retardant.


The additive flame retardant is added to the polymer by mechanical mixing method to make the polymer flame retardant. At present, the additive flame retardant mainly includes organic flame retardant and inorganic flame retardant, halogen flame retardant (organic flame retardant). Chloride and organic bromide) and non-halogen.

Organic is some flame retardants represented by bromine, phosphorus nitrogen, nitrogen and red phosphorus and compounds. Inorganic are mainly antimony trioxide, magnesium hydroxide, aluminum hydroxide, silicon and other flame retardant systems.

Reactive flame retardants participate in the polymerization reaction as a monomer, so the polymer itself contains flame retardant components. Its advantage is that it has less impact on the performance of polymer materials and has long-lasting flame retardancy.

1. The mechanism of action of flame retardants


The mechanism of action of flame retardants is relatively complicated and is not yet fully understood. It is generally believed that the halogen compound undergoes a decomposition reaction when exposed to fire and heat, and the decomposed halogen ion reacts with the polymer compound to produce hydrogen halide. The latter reacts with a large number of active hydroxyl radicals (HO·) that proliferate during the combustion of polymer compounds, reducing its concentration and slowing the burning speed until the flame is extinguished.

Among the halogens, bromine has a greater flame retardant effect than chlorine. The role of phosphorus-containing flame retardants is that they form metaphosphoric acid when they burn, and metaphosphoric acid polymerizes into a very stable multimeric state, which becomes a protective layer of plastics and insulates oxygen.

Flame retardants exert their flame retardant effects through several mechanisms, such as endothermic effect, covering effect, inhibition of chain reaction, and suffocation of non-combustible gases. Most flame retardants achieve the purpose of flame retardancy through the joint action of several mechanisms.


2. Classification of flame retardants

(1) Divided into halogen series, organic phosphorus series, halogen-phosphorus series, nitrogen series, silicon series, aluminum-magnesium series, molybdenum series, etc. according to the types of elements;

(2) According to the flame retardant effect, it can be divided into intumescent flame retardant, char-forming flame retardant, etc.;

(3) According to chemical structure, it can be divided into inorganic flame retardant, organic flame retardant, polymer flame retardant, etc.;

(4) According to the relationship between flame retardant and flame-retardant material, it can be divided into additive flame retardant and reactive flame retardant, and reactive flame retardant participates in the chemical reaction of polymer.


Halogen flame retardant


Halogen flame retardants are currently one of the largest organic flame retardants in the world. Halogen-based flame retardants are mainly used in the electronics and construction industries. About 50 to 100 halogen-containing flame retardants cover most of the market demand.

The reason why halogen flame retardants are paid attention to is that the flame retardant efficiency of halogen flame retardants is high, and the price is moderate. Its performance-price ratio is difficult to compare with other flame retardants. In addition, halogen flame retardants There are many kinds of agents and a wide range of applications, so they are favored by people. However, halogen flame retardants generate more smoke and corrosive gases during thermal cracking or combustion, and are plagued by dioxin problems.

More than 80% of halogen-containing flame retardants are used in electronic/office equipment and construction industries. The main application varieties are styrene and its copolymers, thermoplastic engineering plastics and epoxy resins.


Phosphorus flame retardant


Phosphorus-containing compounds can be used as flame retardants for thermoplastics, thermosetting plastics, fabrics, paper, coatings and adhesives. Such flame retardants include red phosphorus, water-soluble inorganic phosphates, insoluble ammonium polyphosphates, organic phosphates and phosphonates, phosphine oxides, hydrogen bomb hydrocarbyl phosphates and bromoaromatic hydrocarbyl phosphates.


Although halogen flame retardants have high flame retardancy, they have environmental pollution and toxicity problems. Phosphorus flame retardants are very effective flame retardants in addition to several types of polymers such as styrene and polyolefin. The secondary pollution is small, so the flame retardant has attracted people's attention.


Ammonium Phosphate


Monoammonium phosphate (MAP) and diammonium phosphate (DAP) are still effective flame retardants for fibers and fabrics, non-woven fabrics, paper, wood and many other celluloses. They can form phosphoric acid to esterify the cellulose hydroxyl group, and the resulting cellulose is decomposed into charcoal, which changes the thermal degradation process and achieves the purpose of flame retardancy. They are easily soluble in water, so their flame retardancy cannot be sustained. It is currently one of the main components of intumescent flame retardants.


Red phosphorus


Red phosphorus is a very effective flame retardant, which can be used for oxygen-containing polymers, such as PC, PET, PBT, PPE, and it is used more in Europe as a flame retardant for nylon parts. Since red phosphorus reacts with water in the atmosphere to generate toxic phosphine, industrial products need to be stabilized and coated.


Trihydroxy Phosphate (phosphonate)


Trihydroxy phosphate (phosphonate) is used as a diluent when unsaturated polyester is highly filled (such as aluminum hydride, calcium carbonate). It is also used as a synergist in halogenated polyesters, not as effective as antimony oxide, but has good processability. The less volatile trihydroxy phosphates are tributyl phosphate, trioctyl phosphate and tributoxyethyl phosphate.


Dimethyl phosphate contains up to 25% phosphorus and is an extremely effective flame retardant. Its high volatility limits its application. It is suitable for polyurethane rigid foam and high filling thermosetting resin. It is also used as a viscosity diluent in highly filled thermosetting resins. Diethyl ethyl phosphate is relatively stable under the condition of urethane foaming agent and amine catalyst.


Aryl phosphates


Aryl phosphate esters are mainly used in the industry as non-flammable plasticizers for PVC and cellulose acetate and as non-halogen flame retardants for engineering plastics such as PPE and PC/ABS alloys.


Alkylated Triphenyl Phosphate


Aryl phosphate esters are all liquids, and the main alkylation products are made of synthetic isopropyl phenol or isobutyl phenol. The preparation method is to first alkylate phenol and then react with phosphoryl chloride. Therefore the alkylated triaryl phosphate is a mixture.

Among them, tributylphenyl phosphate has better oxidation resistance, but poor plasticity. Trimethyldiphenyl phosphate is the most effective flame retardant for PVC. But it is also the most volatile and is used in Europe. Alkane diaryl phosphonate has better plasticity, and has better low temperature performance when used in PVC, and its smoke generation is less than that of triaryl phosphonate.


2-ethylhexyl diphenyl phosphate


2-Ethylhexyl diphenyl phosphate has been approved by the US Food and Drug Administration for use in food packaging. Isodecyl diphenyl phosphate can be used for PVC cables, especially high-voltage cables, due to its long hydrocarbon group, which is not volatile.


The dimer aryl phosphate is relatively volatile, and its linking group is resorcinol, hydroquinone or bisphenol. They are used in thermoplastics (such as PPE, PC/ABS).


Modified polyphenylene ether (PPE)


Modified polyphenylene ether (PPE) is a blend of PPE and high-impact polystyrene (PS-HI). According to the grade, it generally contains 55%~65% PS-HI. Although phosphate ester does not make PS-HI reach UL 94 flame-retardant grade, it is used in industry for flame-retardant PPE resin and reaches UL 95 V-0 grade. The phosphoric acid generated by the phosphoric acid ester makes the PPE charred to achieve the purpose of flame retardancy. Industrial flame retardants are liquid alkylated triarylphosphonate or dienoate.



Triarylphosphonate


Triaryl phosphonates will volatilize during processing, causing stress fracture. Using less volatile diphosphates can reduce stress fracture. Bisphenol A may be a linking group of quinone diphosphate.


Halogenated phosphate


Halogen-containing alkyl phosphate is mainly used for harder polyurethane foam products. But the thermal stability is poor. However, due to its toxicity, halogen-containing phosphate has been banned by most countries such as the European Union, and it is not recommended in my country.


Phosphorus oxides


Phosphorus oxides have hydrolytically stable P—C bonds, and their P content is higher than that of aryl phosphates, so they are more effective flame retardants. Their diols and triols are active flame retardants for polyurethane and epoxy resins.

Phosphorus compounds, as flame retardants, can inhibit free radical reactions in the condensed phase, and they can also produce glassy substances until the heat transfer and mass transfer are blocked. Organophosphorus flame retardants are considered to be one of the most promising varieties to replace halogenated flame retardants.


Inorganic hydroxide


Inorganic hydroxides are very important flame retardants. Inorganic hydroxide is easy to handle, relatively non-toxic, does not produce toxic and corrosive gases, and suppresses smoke. More importantly, it is cheaper than halogen and phosphorus flame retardant systems.

The proper formulation of this kind of flame retardant can make the material meet a variety of test requirements. Inorganic aluminum hydroxide is the most popular flame retardant for inorganic hydroxides, and is mainly used for synthetic rubber, thermosetting resins and thermoplastics whose processing temperature is below 200°C. Considering the environmental issues of halogen-containing and phosphorus-containing flame retardants, the application of inorganic hydroxide flame retardants has continued to grow.



Aluminum Hydroxide (ATH)


Aluminum hydroxide is one of the most widely used flame retardants. It is a non-toxic, white to light white powder with a relative density of 2.42 and a Mohs hardness of 3.0. When the temperature is heated to higher than 320°C, aluminum hydroxide loses 34.6% of its weight due to water loss.

For polymers whose processing temperature is lower than the decomposition temperature of aluminum hydroxide (190~230℃), aluminum hydroxide is an excellent flame retardant material. It is worth noting that the size of the particle diameter has an effect on thermal stability.


As a flame-retardant material, aluminum hydroxide is used in elastomers, thermosetting resins and thermoplastics. It is also used in large quantities in the styrene-butadiene latex for the production of flame-retardant carpets, as well as in the production of flame-retardant insulated rubber cables and thermal insulation foams. , Conveyor belts and hoses, etc. It can be used in all unsaturated resins, such as laminated large ceilings and walls, used in bathroom appliances, decorative wall panels, various covers, automobile protective covers, truck parts, etc., and electronic components including insulators and circuit boards. It also includes construction equipment and so on.


magnesium hydroxide


Magnesium hydroxide is the second largest sales volume of inorganic hydroxide flame retardants. It is a white to light white lens powder with a relative density of 2.4 and a Mohs hardness of 3.0. When heated to above 450°C, the weight will be reduced by 30.9% (mass fraction) due to the loss of water.


Magnesium hydroxide is used to process thermoplastics and thermosetting resins with a processing temperature of 200 to 225°C. Mainly used for EVAC, PP and blends, ABS and blends, fluoropolymers, PPE and blends, polyimides, etc. Cannot be used for thermoplastic polyester. Magnesium hydroxide is used together with aluminum hydroxide to meet different requirements. Magnesium hydroxide is also used in parts such as wires and cables, racks, building multilayer boards, pipes, and electrical appliances.



Silicon compound


Silicon compounds are a new type of flame retardant. It can play a flame-retardant effect without relying on halogen and phosphorus compounds. Recently, articles and patents related to silicon flame retardants have become new hotspots. All the various compositions of silicon are used as flame retardants in research. The silicon-containing compound has obvious flame retardant effect whether it is used as an additive to a polymer or as a blend with a polymer.

The above is what the editor wants to say about flame retardants. If you have any tris(2-chloropropyl) phosphate flame retardant TCPP, trichloroethyl phosphate flame retardant TCEP, triethyl phosphate flame retardant Please feel free to contact us Taizhou Ruishite New Material Co., Ltd. if you need it, such as the fuel agent IPPP! ! !


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