In the field of flame retardancy for polymer materials, brominated flame retardants occupy an important position due to their high-efficiency flame-retardant properties. Among them, brominated epoxy resin (BER) and brominated polystyrene (BPS) are two mainstream products. Although both are brominated flame retardants, they have significant differences in chemical structure, action mechanism and application effect, which directly affect their adaptability in different material systems.
     BER is a polymer-type flame retardant with a molecular weight of up to 25,000, featuring both flame-retardant and bonding functions, especially suitable for PA6+30% glass fiber and PBT+30% glass fiber systems. Its core advantage lies in the synergistic mechanism: it not only releases bromine free radicals to exert gas-phase flame retardancy during combustion, but also promotes char formation to achieve solid-phase flame retardancy. Meanwhile, the epoxy end groups can chemically react with the amine end groups of PA6, and the carboxyl and hydroxyl end groups of PBT, enhancing the interface bonding between the flame retardant, the matrix and glass fiber, and effectively inhibiting the glass fiber wick effect. In practical applications, the total amount of BER and antimony trioxide only needs 13%, combined with 5% POE-g-MAH to achieve the desired effect. If 3% organic montmorillonite is compounded, the amount of flame retardant can be further reduced, with little impact on the mechanical properties of the material, and the product has a better appearance and whiter color.
     In contrast, BPS is an inert polymer that only acts as a physical filler. Although its bromine content is as high as 60%-68%, it only relies on the pure gas-phase flame-retardant mechanism and requires a high addition amount (about 20%) to achieve the flame-retardant effect. Since there is no chemical reaction with matrices such as PA6 and PBT, BPS tends to aggravate the interface defects between the material and glass fiber, failing to alleviate the wick effect. It not only has low flame-retardant efficiency, but also causes greater negative impacts on the mechanical properties of the material such as toughness, tensile strength and bending strength, and has the risk of migration.
     With the increasing requirements for environmental protection and performance, BER has shown broader application prospects in PA6 and PBT glass fiber reinforced systems due to its advantages of low addition amount, high flame-retardant efficiency and good interface compatibility. However, BPS has relatively limited application scenarios due to its shortcomings such as high addition amount and large loss of mechanical properties. The differences between the two provide clear selection criteria for downstream enterprises, promoting the development of the flame-retardant material industry towards high efficiency and low loss.

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