Research Progress Of ABS Flame Retardant Modification

Research Progress Of ABS Flame Retardant Modification

Abstract

Acrylonitrile-butadiene-styrene (ABS) resin is an excellent thermoplastic material with a wide range of applications in industries such as automotive, electronics, and energy storage. However, its flammability limits its use in fields with high fire-resistant requirements. This paper reviews the latest research progress on flame-retardant ABS, compares the effects of halogenated flame retardants, phosphorus-nitrogen flame retardants, silicon-based flame retardants, and inorganic nano flame retardants on the flame retardancy of ABS, and introduces some of the latest requirements and progress in the environmental protection of flame retardants.

Introduction

Acrylonitrile-butadiene-styrene (ABS) is a ternary copolymer that exhibits a typical “sea-island” two-phase structure at the microscopic level, with butadiene rubber particles dispersed in a continuous phase of styrene-acrylonitrile (SAN). In terms of macroscopic properties, ABS combines the excellent characteristics of its three components. Acrylonitrile endows it with chemical resistance and surface hardness. butadiene provides the polymer with rubber-like toughness. and styrene gives the polymer good rigidity and processability. The synergistic effect of these three components endows ABS with a series of advantages, including chemical resistance, high impact strength, heat resistance, and excellent processability, making it widely used in automotive, consumer electronics, energy storage, and home appliances.

However, ABS is a flammable material with a limiting oxygen index (LOI) of only 18%. It burns rapidly in a horizontal direction and produces a large amount of black smoke during combustion. The combustion mechanism of ABS is complex due to its composition of three main components. It is generally believed that the polybutadiene segment (B segment) contains substituted tertiary carbon atoms, which facilitate the abstraction of hydrogen from butadiene by oxygen, triggering oxidation and accelerating the degradation of ABS. Some researchers also suggest that the generation of highly reactive HO• radicals during ABS combustion is key to determining the combustion rate. When a polymer encounters HO• radicals, it forms polymer radicals and water. In the presence of oxygen, more HO• radicals are produced, sustaining the reaction and ultimately generating CO₂ and H₂O.

The three essential elements for polymer combustion are combustible materials, oxygen, and heat. Interrupting any one or more of these elements can achieve flame retardancy. Therefore, the use of flame-retardant elements can effectively enhance the flame-retardant properties of ABS.

Currently, there are three main methods to improve the flame-retardant performance of ABS:

1.Using additive flame retardants.

2.Using polymers containing flame-retardant elements.

3.Using reactive flame retardants.

In the first method, flame retardants are mainly incorporated into the polymer by physical blending, including halogenated flame retardants, phosphorus-nitrogen flame retardants, and inorganic nano flame retardants. The second method typically involves blending polymers containing flame-retardant elements with resins, such as polyvinyl chloride (PVC) and chlorinated polyethylene (CPE). Both of these methods involve simple mixing of flame retardants or flame-retardant polymers with the base resin, which often affects the processing and mechanical properties of the plastic. The third method involves copolymerizing flame-retardant elements or flame retardants into the base resin during the polymerization process, endowing the polymer with inherent flame-retardant properties. This method has a smaller impact on the plastic's properties but is more complex in synthesis and less versatile. Currently, additive flame retardants are still the primary choice for polymer flame retardancy. This paper reviews the types and current usage of common flame retardants in ABS, focusing on additive flame retardants.

Conclusion

Halogenated flame retardants, such as brominated flame retardants, are widely used in flame-retardant ABS products due to their versatility, high flame retardancy efficiency, and good compatibility with the base resin. However, the flame-retardant effects of halogen-free flame retardants on ABS are currently very limited. With the increasing environmental requirements for materials both domestically and internationally, the demand for halogen-free flame-retardant ABS will inevitably grow in the future. To truly achieve halogen-free flame retardancy in ABS, it is necessary to address the following issues:

On one hand, the char formation in halogen-free flame-retardant ABS needs to be improved. For example, introducing oxygen-containing groups into the ABS structure or adding oxygen-containing polymers can promote char formation, thereby enhancing flame retardancy. On the other hand, synergistic flame-retardant approaches may be necessary. By leveraging the synergistic effects of different flame retardants, the flame-retardant performance of ABS can be improved.

Halogen-free Flame Retardants for ABS:

Halogen-free flame retardants for ABS mainly include inorganic flame retardants (such as magnesium hydroxide and aluminum hydroxide) and organic flame retardants (such as phosphorus-nitrogen flame retardants and silicon-based flame retardants). However, these flame retardants have several drawbacks. For example, magnesium hydroxide requires a high loading level (above 50%) to achieve effective flame retardancy, which significantly reduces the mechanical properties of the material. Additionally, the addition of these flame retardants often leads to a decrease in impact strength. For instance, when magnesium hydroxide is added to ABS at high levels, the impact strength can drop by over 70%. This is primarily due to the poor compatibility between inorganic flame retardants and the polymer matrix, which disrupts the material's mechanical integrity.

In recent years, research on renewable bio-based flame retardants has attracted increasing attention. Bio-based flame retardants, with their excellent ability to form char, can serve as a natural and efficient carbon source in intumescent flame-retardant (IFR) systems. However, studies on their application in ABS flame retardancy are still rare. Additionally, further improvements are needed in the compatibility of bio-based flame retardants with polymer matrices, their flame-retardant effectiveness, and the overall comprehensive properties of the resulting composites.

Although additive flame retardants currently dominate the market, research on intrinsic flame retardancy is also growing. Intrinsic flame retardancy has minimal impact on the properties of the base material and is environmentally friendly. However, it is still primarily in the research stage, with few products actually being applied. With the increasing environmental requirements both domestically and internationally, how to develop highly efficient and environmentally friendly intrinsic flame-retardant polymer materials has become an urgent issue for researchers to address.

In conclusion, Yinsu Flame Retardant Company has also dedicated significant efforts to the development of more environmentally friendly and efficient flame retardants specifically for ABS. The company has introduced products such as ABS-P-20M and FRP-750A, which are designed to meet the stringent requirements of modern applications. Additionally, the company has developed brominated antimony masterbatches that can effectively replace traditional antimony trioxide, enhancing the flame retardancy of ABS without compromising its mechanical properties. These innovations highlight Yinsu's commitment to advancing the flame retardant industry through sustainable and high-performance solutions.