ABS plastic particles have good mechanical properties and processing properties, but they are flammable and have an oxygen index of only 18.2%, which limits their application in fields with high flame retardancy requirements such as electronic appliances and automotive interiors. In order to meet the safety standards in related fields, ABS plastic particles need to be flame-retardant modified. Currently, the commonly used methods include additive flame retardant, reactive flame retardant, nanocomposite flame retardant, etc. These methods improve the flame retardancy of ABS plastics through different mechanisms.
Additive flame retardant method is the most commonly used flame retardant modification method, which achieves the flame retardant effect by directly adding flame retardants to ABS plastic particles. According to the composition of flame retardants, they can be divided into halogen flame retardants, phosphorus flame retardants, nitrogen flame retardants and metal hydroxide flame retardants. Halogen flame retardants (such as decabromodiphenylethane and tetrabromobisphenol A) have high flame retardancy, release hydrogen halides during combustion, capture free radicals in the combustion reaction, interrupt chain reactions, and thus inhibit combustion; but they produce toxic and harmful gases during combustion, and have poor environmental protection, and their application is gradually restricted. Phosphorus-based flame retardants (such as red phosphorus and phosphate esters) decompose under heat to form phosphoric acid, metaphosphoric acid, etc., forming a molten glass-like protective layer on the surface of the material, isolating oxygen and heat, while promoting carbonization and reducing the generation of flammable gases. Nitrogen-based flame retardants (such as melamine) decompose at high temperatures to produce non-flammable gases such as nitrogen and ammonia, diluting the oxygen concentration, reducing the combustion rate, and have the characteristics of low smoke and non-toxicity. Metal hydroxide flame retardants (such as aluminum hydroxide and magnesium hydroxide) absorb a large amount of heat when they are decomposed under heat, reducing the surface temperature of the material, while releasing water vapor to dilute the flammable gas. The metal oxides generated after decomposition can also play a role in heat insulation and oxygen isolation. The additive flame retardant method is simple to operate and low in cost, but it may affect the mechanical properties of ABS plastics, and the flame retardant is easy to migrate and precipitate.
The reactive flame retardant method is to introduce monomers containing flame retardant elements into the ABS molecular chain through chemical reactions such as copolymerization and grafting, so that flame retardant properties become the inherent characteristics of the material. For example, flame retardant ABS resin is prepared by copolymerizing phosphorus or bromine-containing flame retardant monomers with acrylonitrile, butadiene, and styrene. The advantages of this method are that the flame retardant is firmly combined with the ABS molecules, is not easy to migrate and precipitate, has little effect on the mechanical properties of the material, and has a lasting flame retardant effect; the disadvantages are that the synthesis process is complicated, the cost is high, and the equipment and technology requirements are strict. It is currently used to prepare high-performance flame retardant ABS materials.
The nanocomposite flame retardant method is a new flame retardant technology developed in recent years. By adding nano-scale flame retardant materials (such as nanoclay, carbon nanotubes, and nano metal oxides) to ABS plastics, nanocomposites are formed to improve flame retardant properties. Nanomaterials have unique size effects and surface effects, and a small amount of addition can significantly improve the flame retardant properties of the material. For example, after nanoclay is dispersed in the ABS matrix, it can form a barrier layer to delay the transfer of heat and oxygen, and promote the formation of a carbon layer; carbon nanotubes have excellent thermal conductivity and mechanical properties, can build a thermal conductive network in the material, accelerate heat transfer, reduce the surface temperature of the material, and enhance the strength and stability of the carbon layer. The nanocomposite flame retardant method can not only improve the flame retardant properties of ABS plastics, but also improve its mechanical properties and processing properties. However, the dispersibility and compatibility of nanomaterials are key issues that need to be solved, otherwise it will affect the flame retardant effect and material properties.
The synergistic flame retardant method is to use two or more different types of flame retardants in combination, and use the synergistic effect between flame retardants to improve flame retardant efficiency, reduce the amount of flame retardants, and reduce the impact on material properties. For example, when halogen flame retardants are compounded with antimony trioxide, the antimony halide generated by the reaction of antimony trioxide and hydrogen halide has a stronger flame retardant effect; when phosphorus-nitrogen flame retardants are compounded, phosphorus flame retardants promote carbonization, and nitrogen flame retardants produce non-flammable gases. The two work synergistically to improve flame retardant properties. The synergistic flame retardant method can flexibly adjust the flame retardant formula according to different application requirements, optimize the flame retardant effect and material properties, and is a flame retardant modification method with broad application prospects.
The surface modification flame retardant method improves the flame retardant properties of the material by treating the surface of ABS plastic particles, introducing flame retardant groups or forming flame retardant coatings. For example, flame retardant monomers are grafted onto the surface of ABS using plasma treatment, chemical vapor deposition and other technologies, or flame retardant coatings (such as intumescent flame retardant coatings) are applied. Intumescent flame retardant coatings expand when heated to form a porous carbon foam layer, which plays a role in heat insulation, oxygen isolation, and preventing the escape of flammable gases. The surface modification flame retardant method has little effect on the internal properties of the material, and local flame retardant treatment can be performed as needed, but the flame retardant effect may not be as long-lasting as other methods, and the adhesion and durability of the coating need to be further improved.
In practical applications, the selection of flame retardant modification methods requires comprehensive consideration of factors such as the application field, performance requirements, cost budget, and environmental regulations of ABS plastics. For example, the electronic and electrical field has high requirements for flame retardant properties and environmental protection, and reactive flame retardant methods or nano-composite flame retardant methods can be used; in the field of architectural decoration, additive flame retardant methods and synergistic flame retardant methods can be combined to meet flame retardant requirements while controlling costs. With the increasing awareness of environmental protection and increasingly stringent regulations, the development of high-efficiency, low-toxic, and environmentally friendly flame-retardant modification technology will be the development direction of flame-retardant treatment of abs plastic particles.
