Plastics are widely used in industry, agriculture and daily life, but almost all plastics are flammable, and some of them also generate a large amount of harmful gases and smoke when they are burned. The resulting fire hazard has become a global concern. . Currently, the addition of effective flame retardants is a common method in flame retardant technology. Halogen-based flame retardants have a good balance of cost and performance, and have a wide range of applications. They still occupy the dominant position of plastic flame-retardant formulations. However, halogen-based flame retardants emit a large amount of smoke, and the hydrogen halide gas released is highly corrosive, potentially causing secondary hazards. According to reports, PBDE flame-retarded plastics generate PBDF when burned. This substance has a strong carcinogenic effect, which is what Western countries call “Dioxin Is-sueâ€. Therefore use is limited. Environmental groups in the European Community have clearly published laws prohibiting the entry of plastics containing halogen-containing flame retardants into the European market. Based on the understanding of environmental protection issues, plastic flame-retardant tends to change without halogenation.
At present, the use of inorganic flame retardants in Europe accounted for 50%, the United States accounted for 60%, Japan accounted for 64%, it can be seen that all countries are the most inorganic series of flame retardants, and our country in this area is not enough development efforts, only 17 %. In recent years, the development of inorganic flame retardants in China has attracted extensive attention and is rapidly developing. According to the typical varieties of halogen-free flame retardants, they are classified into inorganic metal compounds, phosphorus compounds, nitrogen compounds, and silicon compounds.
1. Inorganic Metal Compounds The most representative of these are hydrated metal compounds, such as Al(OH)3/Mg(OH)2, which make up the majority of halogen-free flame retardants. As a flame retardant, it is characterized by the fact that it must be blended in large quantities to meet the UL94 V0 flame retardant requirements. However, they increase the viscosity of the composition, reduce the molding processability, water resistance, and mechanical properties, and do not generate toxic gases during combustion. Flammability and low smoke effect.
The dehydration endotherm temperature of aluminum hydroxide is 235-350°C and the heat absorption is 1968J/g, which can inhibit the temperature rise of early materials. At present, the flame-retardant properties are mainly improved by the following methods.
1 Surface activation Coupling agents improve the processability, water resistance, and electrical properties of aluminum hydroxide. For example, Lubral, which is surface treated by Alcoa, USA; H-34, H-34HL, and H-312, Showa Light Metals, Japan.
2 Superfine particle diameter, particle size distribution, and ultra-thin particle shape can improve the dehydration temperature and improve the processability. For example, the mechanically milled superfine grades Micra 1910 and Mi-cra 932 of American Salem Industry Co., Ltd. have an average particle size of only 0.6 μm. The particle size of superfine grades in Shandong Aluminum Plant can be as small as 0.5 μm.
3 Combined use of the composite hydrogenated alumina and certain inorganic compounds can improve flame retardancy and smoke suppression, such as compounding with ammonium molybdate, zinc oxide, antimony oxide, red phosphorus, etc.
4 Reinforced Fibre The sodium alfa-aluminate [NaAl(OH)2CO3] flame retardant developed by Alcoa of the United States is used for flame retardant and reinforcement of plastics. The special crystalline Mg-Al basic salt developed by the Jiangsu Seawater Comprehensive Utilization Institute can not only impart flame retardancy to plastics, but also have fiber filling effect. Since aluminum hydroxide is environmentally friendly and inexpensive, its use rate has been kept at a relatively high rate of growth. The proportion of flame retardants in total use has increased from about 30% in 1972-1977 to nearly 50 in 1984. %, up until now, this ratio has remained stable.
Magnesium hydroxide decomposes at 340-490°C, and the heat absorption is 783J/g. It takes a relatively high temperature to start the dehydration reaction, and the heat absorption is small. It is not good for inhibiting the temperature rise of material than aluminum hydroxide, but the carbonization of the polymer. The role is better than aluminum hydroxide. Magnesium hydroxide also needs surface activation to improve the interface properties with the matrix resin. In foreign countries, modified magnesium hydroxide has been widely used in PP, PE, PS, PVC, ABS, PA and other engineering plastics, rubber and elastomers.
The use of a mixture of magnesium hydroxide and aluminum hydroxide as a flame retardant can have its own advantages. In recent years, the research on the synergistic effect of inorganic hydroxide flame-retardant is also very popular. The common synergists in Al(OH)3/Mg(OH)2 flame-retardant systems include red phosphorus, phosphate ester, and ammonium polyphosphate. Silicone and so on. Other inorganic metal compound flame retardants include zinc borate, aluminum compounds, tin compounds, zirconium oxide, copper oxide, cuprous oxide and other metal compounds. In recent years, the development of composite flame retardants and their synergies are valuable development directions. . With the warming of nanomaterials, polymer/nanomaterials may become a new generation of flame-retardant polymer materials. At present, nylon 6/layered silicate (PA6/LS) is being developed as a new flame retardant material.
2. Phosphorus-based phosphorus flame retardants also play an important role in halogen-free flame retardants. According to the composition and structure can be divided into inorganic and organic phosphorus flame retardants, the former mainly red phosphorus and phosphate, the latter mainly phosphate, phosphite and phosphonate and so on.
Inorganic phosphorus flame retardants such as red phosphorus, ammonium phosphate and ammonium polyphosphate have been used earlier, and many industrial products have been introduced abroad. In Europe, more and more applications of red phosphorus are mainly used for polyamides, epoxy resins, polyolefins, and polyurethanes, and are supplied with easy-to-handle masterbatches, with the help of coating and the addition of stabilizers to reduce the release of phosphorus by red phosphorus. Red phosphorus not only has its own strong flame retardant effect, but also can form a synergistic flame retardant system with other substances to enhance the flame-retardant efficiency. According to reports, Japan Risoo Co., Ltd. and another flame retardant company jointly developed a new type of flame retardant based on heat-expandable graphite and red phosphorus.
Ammonium polyphosphate is mainly used for swelling catalysts, and the expansion formula of ammonium polyphosphate and carbon-containing nitrogen-containing resins has found industrial applications. Clariant has introduced a highly efficient intumescent PN flame retardant specifically for PP and PP, under the designation Exolit AP750 and AP751. The halogen-free flame-retardant PP and non-halogen flame-retardant PP are used in alternative manufacturing in Western Europe. The flame-retardant ABS or flame-retardant ABS/PC of electronic components can achieve high efficiency and low cost. In addition, some of the new hypophosphite additives produced by Clariant are used in thermoplastics, in particular polyesters and ABS have a significant effect.
The organic phosphorus flame retardant is characterized by its dual functions of flame retardant and plasticization. It can fully achieve halogen-free flame retardant, so that when the plastic molding process flow performance becomes better. Combustion residues can be suppressed, resulting in fewer toxic gases and corrosive gases than halogen flame retardants. In addition, it has good compatibility with the resin and maintains the transparency of the resin. Organophosphorus flame retardants are developing with higher functionality and high added value.
New tetraaryl aryl diphosphates have been used industrially in thermoplastics and may have a gas phase effect, but may also produce a barrier layer, mainly for some highly functional styrenic copolymers such as PPO/HIPS And PC/ABS and so on. DSM's melamine polyphosphate MELA PUR 200 for polyamide 66 has higher thermal stability than existing melamine polyphosphates and is used for flame-retardant glass-filled nylon 66 with higher processing temperatures. The study found that the use of synergists can effectively improve the flame retardant effect of phosphides. Such as NP synergism mechanism, there are synergies between various metal oxides and salts and phosphorus, but sometimes antagonistic effects such as (zn)3(BO3)2, Fe2O3 and MoO3 are effective, while Sn0, Pb0 and Bi2O3 etc. It is harmful, and the combination of phosphate ester and antimony trioxide is often confrontational.
3. Nitrogen-based nitrogen-based flame retardants develop relatively late in comparison with other flame-retardants, and its flame retardancy is not very good. It is often used in combination with other flame retardants. The addition of nitrogen can promote the phosphorization of the phosphorus system, which has a synergistic effect. As mentioned above DSM Melamine Polyphosphate MELA PUR 200. In addition, nitrogen and lanthanoid also synergistic effect.
Nitrogen-based flame retardants mainly include melamine and melamine cyanurate, which can be used for polyurethanes and polyamides. In addition, there are melamine formaldehyde condensates, guanidine salts, hydrazine condensates and the like. The barium sulfamate in the yttrium compound is low toxic and soluble in water and is mainly used for wallpapers. At present, the development of high-nitrogen content, high-temperature decomposition type, and nitrogen-based flame retardants that are compatible with polymers is a major research topic.
4. In recent years, silicon has attracted worldwide attention as a low-damage flame retardant. Inorganic silicon is mainly SiO2, which has both reinforcing and flame retardant effects. Its flame retardant mechanism is that when the plastic is burned, it forms a silicon dioxide coating and plays a dual role of insulation and shielding. SiO2 is rarely used alone, and often used with halides. . The research, development, and use of silicone have long been attracting attention. As a class of polymer flame retardants, it is highly efficient, non-toxic, low-smoke, drip-proof, and non-polluting, especially because it is a polymer material. Therefore, the effect on the performance of the product is very small and it is a promising organic flame retardant. The flame-retardant mechanism is: when the plastic is burning, the silicone generates silicon carbide. This silicon carbide insulating layer can prevent the volatiles generated by combustion from escaping, and can prevent the melt from dripping due to the contact between oxygen and the resin, thereby achieving flame retardancy. the goal of.
Silicone flame retardants include silicone oils, silicone resins, silicone rubbers, and organosilanol amides. US GE's SFR-100 has a good flame retardant effect on polyolefins, while improving the processing and mechanical properties of the resin, can give the substrate excellent flame retardancy and smoke suppression, very strict and ordinary resistance for fire safety Where the fuel system is not suitable. Silicone powder developed by Dow Cornimg, USA is a highly efficient flame retardant. It can be used for polyolefin, polyester, polystyrene and nylon according to different models. China's Foshan City, Guangdong Guanghua Filling Chemicals Co., Ltd. has also developed a silicone powder for a variety of plastic flame retardant, incompatibility. Can improve the processing and plastic surface smoothness. In addition, the National University of Defense Technology uses organosilicon synergistic Al(OH)3/Mg(OH)2 to increase the oxygen index of the system.
The polysiloxane PC jointly developed by NEC Japan and Japan's SumitomoDow, a polycarbonate resin supplier, is one of the latest halogen-free flame retardant resins. This silicon-based flame-retardant PC has achieved the German “Blue Sky†eco-label certification and has been sold to electrical and other industrial manufacturers worldwide. At present, the development of flame retardants has been developed towards multi-functionality. Increasing the flame-retardant efficiency, reducing the amount of use, and reducing the harm to health and environment have drawn increasing attention. Therefore, the halogen-free trend is becoming the main trend in the development and application of flame retardants.
At present, the use of inorganic flame retardants in Europe accounted for 50%, the United States accounted for 60%, Japan accounted for 64%, it can be seen that all countries are the most inorganic series of flame retardants, and our country in this area is not enough development efforts, only 17 %. In recent years, the development of inorganic flame retardants in China has attracted extensive attention and is rapidly developing. According to the typical varieties of halogen-free flame retardants, they are classified into inorganic metal compounds, phosphorus compounds, nitrogen compounds, and silicon compounds.
1. Inorganic Metal Compounds The most representative of these are hydrated metal compounds, such as Al(OH)3/Mg(OH)2, which make up the majority of halogen-free flame retardants. As a flame retardant, it is characterized by the fact that it must be blended in large quantities to meet the UL94 V0 flame retardant requirements. However, they increase the viscosity of the composition, reduce the molding processability, water resistance, and mechanical properties, and do not generate toxic gases during combustion. Flammability and low smoke effect.
The dehydration endotherm temperature of aluminum hydroxide is 235-350°C and the heat absorption is 1968J/g, which can inhibit the temperature rise of early materials. At present, the flame-retardant properties are mainly improved by the following methods.
1 Surface activation Coupling agents improve the processability, water resistance, and electrical properties of aluminum hydroxide. For example, Lubral, which is surface treated by Alcoa, USA; H-34, H-34HL, and H-312, Showa Light Metals, Japan.
2 Superfine particle diameter, particle size distribution, and ultra-thin particle shape can improve the dehydration temperature and improve the processability. For example, the mechanically milled superfine grades Micra 1910 and Mi-cra 932 of American Salem Industry Co., Ltd. have an average particle size of only 0.6 μm. The particle size of superfine grades in Shandong Aluminum Plant can be as small as 0.5 μm.
3 Combined use of the composite hydrogenated alumina and certain inorganic compounds can improve flame retardancy and smoke suppression, such as compounding with ammonium molybdate, zinc oxide, antimony oxide, red phosphorus, etc.
4 Reinforced Fibre The sodium alfa-aluminate [NaAl(OH)2CO3] flame retardant developed by Alcoa of the United States is used for flame retardant and reinforcement of plastics. The special crystalline Mg-Al basic salt developed by the Jiangsu Seawater Comprehensive Utilization Institute can not only impart flame retardancy to plastics, but also have fiber filling effect. Since aluminum hydroxide is environmentally friendly and inexpensive, its use rate has been kept at a relatively high rate of growth. The proportion of flame retardants in total use has increased from about 30% in 1972-1977 to nearly 50 in 1984. %, up until now, this ratio has remained stable.
Magnesium hydroxide decomposes at 340-490°C, and the heat absorption is 783J/g. It takes a relatively high temperature to start the dehydration reaction, and the heat absorption is small. It is not good for inhibiting the temperature rise of material than aluminum hydroxide, but the carbonization of the polymer. The role is better than aluminum hydroxide. Magnesium hydroxide also needs surface activation to improve the interface properties with the matrix resin. In foreign countries, modified magnesium hydroxide has been widely used in PP, PE, PS, PVC, ABS, PA and other engineering plastics, rubber and elastomers.
The use of a mixture of magnesium hydroxide and aluminum hydroxide as a flame retardant can have its own advantages. In recent years, the research on the synergistic effect of inorganic hydroxide flame-retardant is also very popular. The common synergists in Al(OH)3/Mg(OH)2 flame-retardant systems include red phosphorus, phosphate ester, and ammonium polyphosphate. Silicone and so on. Other inorganic metal compound flame retardants include zinc borate, aluminum compounds, tin compounds, zirconium oxide, copper oxide, cuprous oxide and other metal compounds. In recent years, the development of composite flame retardants and their synergies are valuable development directions. . With the warming of nanomaterials, polymer/nanomaterials may become a new generation of flame-retardant polymer materials. At present, nylon 6/layered silicate (PA6/LS) is being developed as a new flame retardant material.
2. Phosphorus-based phosphorus flame retardants also play an important role in halogen-free flame retardants. According to the composition and structure can be divided into inorganic and organic phosphorus flame retardants, the former mainly red phosphorus and phosphate, the latter mainly phosphate, phosphite and phosphonate and so on.
Inorganic phosphorus flame retardants such as red phosphorus, ammonium phosphate and ammonium polyphosphate have been used earlier, and many industrial products have been introduced abroad. In Europe, more and more applications of red phosphorus are mainly used for polyamides, epoxy resins, polyolefins, and polyurethanes, and are supplied with easy-to-handle masterbatches, with the help of coating and the addition of stabilizers to reduce the release of phosphorus by red phosphorus. Red phosphorus not only has its own strong flame retardant effect, but also can form a synergistic flame retardant system with other substances to enhance the flame-retardant efficiency. According to reports, Japan Risoo Co., Ltd. and another flame retardant company jointly developed a new type of flame retardant based on heat-expandable graphite and red phosphorus.
Ammonium polyphosphate is mainly used for swelling catalysts, and the expansion formula of ammonium polyphosphate and carbon-containing nitrogen-containing resins has found industrial applications. Clariant has introduced a highly efficient intumescent PN flame retardant specifically for PP and PP, under the designation Exolit AP750 and AP751. The halogen-free flame-retardant PP and non-halogen flame-retardant PP are used in alternative manufacturing in Western Europe. The flame-retardant ABS or flame-retardant ABS/PC of electronic components can achieve high efficiency and low cost. In addition, some of the new hypophosphite additives produced by Clariant are used in thermoplastics, in particular polyesters and ABS have a significant effect.
The organic phosphorus flame retardant is characterized by its dual functions of flame retardant and plasticization. It can fully achieve halogen-free flame retardant, so that when the plastic molding process flow performance becomes better. Combustion residues can be suppressed, resulting in fewer toxic gases and corrosive gases than halogen flame retardants. In addition, it has good compatibility with the resin and maintains the transparency of the resin. Organophosphorus flame retardants are developing with higher functionality and high added value.
New tetraaryl aryl diphosphates have been used industrially in thermoplastics and may have a gas phase effect, but may also produce a barrier layer, mainly for some highly functional styrenic copolymers such as PPO/HIPS And PC/ABS and so on. DSM's melamine polyphosphate MELA PUR 200 for polyamide 66 has higher thermal stability than existing melamine polyphosphates and is used for flame-retardant glass-filled nylon 66 with higher processing temperatures. The study found that the use of synergists can effectively improve the flame retardant effect of phosphides. Such as NP synergism mechanism, there are synergies between various metal oxides and salts and phosphorus, but sometimes antagonistic effects such as (zn)3(BO3)2, Fe2O3 and MoO3 are effective, while Sn0, Pb0 and Bi2O3 etc. It is harmful, and the combination of phosphate ester and antimony trioxide is often confrontational.
3. Nitrogen-based nitrogen-based flame retardants develop relatively late in comparison with other flame-retardants, and its flame retardancy is not very good. It is often used in combination with other flame retardants. The addition of nitrogen can promote the phosphorization of the phosphorus system, which has a synergistic effect. As mentioned above DSM Melamine Polyphosphate MELA PUR 200. In addition, nitrogen and lanthanoid also synergistic effect.
Nitrogen-based flame retardants mainly include melamine and melamine cyanurate, which can be used for polyurethanes and polyamides. In addition, there are melamine formaldehyde condensates, guanidine salts, hydrazine condensates and the like. The barium sulfamate in the yttrium compound is low toxic and soluble in water and is mainly used for wallpapers. At present, the development of high-nitrogen content, high-temperature decomposition type, and nitrogen-based flame retardants that are compatible with polymers is a major research topic.
4. In recent years, silicon has attracted worldwide attention as a low-damage flame retardant. Inorganic silicon is mainly SiO2, which has both reinforcing and flame retardant effects. Its flame retardant mechanism is that when the plastic is burned, it forms a silicon dioxide coating and plays a dual role of insulation and shielding. SiO2 is rarely used alone, and often used with halides. . The research, development, and use of silicone have long been attracting attention. As a class of polymer flame retardants, it is highly efficient, non-toxic, low-smoke, drip-proof, and non-polluting, especially because it is a polymer material. Therefore, the effect on the performance of the product is very small and it is a promising organic flame retardant. The flame-retardant mechanism is: when the plastic is burning, the silicone generates silicon carbide. This silicon carbide insulating layer can prevent the volatiles generated by combustion from escaping, and can prevent the melt from dripping due to the contact between oxygen and the resin, thereby achieving flame retardancy. the goal of.
Silicone flame retardants include silicone oils, silicone resins, silicone rubbers, and organosilanol amides. US GE's SFR-100 has a good flame retardant effect on polyolefins, while improving the processing and mechanical properties of the resin, can give the substrate excellent flame retardancy and smoke suppression, very strict and ordinary resistance for fire safety Where the fuel system is not suitable. Silicone powder developed by Dow Cornimg, USA is a highly efficient flame retardant. It can be used for polyolefin, polyester, polystyrene and nylon according to different models. China's Foshan City, Guangdong Guanghua Filling Chemicals Co., Ltd. has also developed a silicone powder for a variety of plastic flame retardant, incompatibility. Can improve the processing and plastic surface smoothness. In addition, the National University of Defense Technology uses organosilicon synergistic Al(OH)3/Mg(OH)2 to increase the oxygen index of the system.
The polysiloxane PC jointly developed by NEC Japan and Japan's SumitomoDow, a polycarbonate resin supplier, is one of the latest halogen-free flame retardant resins. This silicon-based flame-retardant PC has achieved the German “Blue Sky†eco-label certification and has been sold to electrical and other industrial manufacturers worldwide. At present, the development of flame retardants has been developed towards multi-functionality. Increasing the flame-retardant efficiency, reducing the amount of use, and reducing the harm to health and environment have drawn increasing attention. Therefore, the halogen-free trend is becoming the main trend in the development and application of flame retardants.
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