How much do you know about flame retardants? -Melamine polyphosphateHow 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 Chloride and organic bromide) and non-halogen.
Organic is some flame retardants represented by bromine series, phosphorus nitrogen series, nitrogen series and red phosphorus and compounds. Inorganic are mainly antimony trioxide, magnesium hydroxide, aluminum hydroxide, silicon series and other flame retardant systems.
Reactive flame retardants are used as a monomer to participate in the polymerization reaction, 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 flame retardant
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 their concentration and slowing down the burning speed until the flame goes out.
Among the halogens, bromine has greater flame retardancy 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 isolates 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.
Halogen flame retardant
02 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, charred 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 retardants are 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 main reason why halogen flame retardants are paid attention to is that halogen flame retardants have high flame retardant efficiency and moderate prices. The 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 applications 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.
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 is a very effective flame retardant, which can be used for oxygen-containing polymers, such as PC, PET, PBT, PPE. It is used more as a flame retardant for nylon parts in Europe. 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 phosphonate (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 polyester, 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. Suitable for polyurethane rigid foam, high-fill thermosetting resin. It is also used as a viscosity diluent in highly filled thermosetting resins. Diethyl ethyl phosphate is relatively stable when urethane has a blowing agent and an amine catalyst.
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 ester has low volatility, 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 phosphate ester makes the PPE charred to achieve the purpose of flame retardancy. Industrial flame retardants are liquid alkylated triarylphosphonates or dienoates.
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.
Halogen-containing alkyl phosphate is mainly used in polyurethane harder foam products. But the thermal stability is poor. However, due to its toxicity, halogen-containing phosphates have been banned by most countries such as the European Union and are not recommended in my country.
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 and mass transfer barriers. Organophosphorus flame retardants are considered to be one of the most promising varieties to replace halogenated flame retardants.
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, and more importantly, it is cheaper than halogen and phosphorus flame retardant systems.
This kind of flame retardant can meet a variety of testing requirements by adopting appropriate formulations. Inorganic aluminum hydroxide is the most popular flame retardant for inorganic hydroxides, and is mainly used for synthetic rubber, thermosetting resin and thermoplastics whose processing temperature is below 200°C. Considering the environmental problems 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 widely used in the production of flame-retardant carpets in styrene-butadiene latex, in the production of flame-retardant insulated rubber cables and thermal insulation foams. , Conveyor belt and hose, 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 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 200~225℃. Mainly used in 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 compounds are new flame retardants. It can play a flame-retardant effect without relying on halogen and phosphorus compounds. Recently, articles and patents on silicon flame retardants have become new hotspots. All 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 a polymer additive or a blend with a polymer.
Major global flame retardant manufacturers:
1. Israel Chemical Industry (ICL)-halogenated flame retardant and halogen-free flame retardant
Company profile: Israel Chemical Group is the largest chemical company in Israel. Founded in 1968, it was formed by the merger of a number of state-owned mining companies in the Dead Sea Chemical Plant and the Negev Desert. Its core business includes fertilizers, industrial chemicals, and high-performance products.
Main products: bromine flame retardants, phosphorus flame retardants, magnesium hydroxide flame retardants.
Official website: http://www.icl-group.com/
2. Albemarle Corporation
Company profile: American Albemarle is one of the major manufacturers of brominated flame retardants in the world. Headquartered in Virginia, USA. The company is listed on the New York Stock Market and its business covers more than 100 countries and regions around the world.
Main products: both halogen-free and halogen-free flame retardants: SAYTEX series are halogen-free, MAGNIFIN series are halogen-free
Official website: http://www.albemarle.com
3. Daihachi-halogen-free flame retardant
Company profile: Founded in 1919, it is a world-renowned manufacturer of phosphorus series flame retardants, mainly producing flame retardant and plasticizer products.
Main products: halogen-free phosphate flame retardants, such as TMP, TEP, TPP, CR series, and halogen phosphate flame retardants, such as TMPCC.
Official website: http://www.daihachics.com/pro.html
4. Lanxess Group (Lanxess)
Company profile: LANXESS is a German specialty chemicals group with its headquarters and main business operations in Cologne. In 2004, Bayer Group carried out a strategic reorganization and spin-off, divesting its chemical business and part of its polymer business, and LANXESS was born.
Main products: Both halogenated and halogen-free flame retardants: DE, BA, PO, DP series all contain halogen, Firemaster series halogen-free, Emerald Innovation?, Firemaster?, antimony-flame retardant synergist and Smoke suppressant, etc.
Official website: http://lanxess.cn/cn/home-china/
5. Clariant (Halogen-free flame retardant: OP series halogen-free)
Company profile: Clariant is the world's leading specialty chemical products company. Clariant's global organization network is distributed on five continents, composed of more than 100 group companies, and currently has 23,000 employees. Clariant is headquartered in Muttenz near Basel (Switzerland) and has annual sales of more than 7 billion Swiss francs.
Main product: Exolit based on phosphorus chemistry application.
6. Royal DSM (Royal DSM)
Company introduction: The Royal Dutch DSM Group is an international nutrition and health products, chemical raw materials and pharmaceuticals group, headquartered in the Netherlands, currently has more than 200 institutions in Europe, Asia, North and South America, and has 22,000 worldwide Employees.
Main products: halogen-free flame retardants, such as F series, L series, T series and X series.
Official website: http://www.dsm.com/countrysites/dsm-china/zh_CN/home.html
7. TOSOH corporation-halogenated flame retardant
Company profile: Japan Tosoh Corporation was established in Yamaguchi Prefecture, Japan in 1935. It was originally a professional enterprise producing caustic soda and soda ash. The company's predecessor was TOYO SODA Co., Ltd. (TOYO SODA), and in 1987 changed its name to the current Tosoh Corporation.
Main products: Brominated flame retardants, such as FLAMECUT.
Official website: http://www.tosoh.co.jp/
8. American Ferro company-halogenated flame retardant
Company profile: Flow Company is one of the world's largest manufacturers of special materials. The company was founded in 1919 and has now developed into a listed company with annual sales of more than 2 billion US dollars.
Main products: Brominated flame retardants, such as Pyro Chek series.
Official website: http://www.ferro.com/
Company profile: Hebrew is a global chemical product supplier integrating scientific research, production, sales and after-sales service. It is committed to rubber, plastics,