Basic knowledge of flame-retardant polypropylene

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Basic knowledge of flame-retardant polypropylene ① Halogen-antimony system, that is, the gas-phase flame-retardant mechanism. Common halogen-based flame retardants include decabromodiphenyl ether, hexabromocyclododecane, octabromodiphenyl ether, and tetrabromobisphenol A; when combined with the flame retardant synergist antimony trioxide, they offer the advantage of requiring low addition amounts while providing excellent flame retardant effects. However, halogen-based flame retardants have been criticized by environmental protection organizations, to the point that in some places they are restricted and their use is explicitly prohibited. However, countries such as the United States and Japan **still allow their use; therefore, for China, which is a developing country, halogen-based flame retardants will remain in use for at least another 10 years. 　　②PP is treated with bromoalkyl phosphates. These flame retardants possess a P-Br synergistic effect, which results in a significant flame-retardant effect; at the same time, they improve the rheology and processability of PP, with little impact on its physical and mechanical properties. 　　③Over the past decade, in the field of PP flame-retardant technology, intumescent flame retardants developed by Professor Camino from the University of Turin in Italy have played a significant role. These PN-type flame retardants are characterized by high efficiency, excellent thermal and optical stability, low toxicity, low smoke production, and low corrosivity; they have little impact on processing and mechanical properties, and do not cause environmental pollution. In PP, adding just 2530 parts is sufficient to achieve UL94 V-0 rating. There have just been reports of the production of intumescent flame retardant products in the domestic market. 　　④Flame-retardant polypropylene based on the graft copolymer of penta-bromobenzyl acrylate and ethylene-propylene-diene monomer rubber. This type of flame-retreated PP possesses high impact strength and can be used as an engineering plastic in certain applications. 　　⑤Flame-retardant polypropylene with inorganic fillers: The so-called inorganic fillers refer to aluminum hydroxide and magnesium hydroxide, which possess flame-retardant and smoke-suppressing properties. However, to achieve the desired results, particleization and surface treatment are key technologies applied to different plastics. Careful selection is required for the surfactant to be used, ensuring good compatibility with the plastic, uniform dispersion within it, without significantly affecting the plastic’s mechanical properties. Since ATH and magnesium hydroxide can provide flame-retardant and smoke-suppressing effects within different temperature ranges, their combined use enables plastics to maintain flame-retardant properties over a wider temperature range. It should be emphasized here that when treating PP with magnesium hydroxide, in order to achieve better flame-retardant properties and appropriate mechanical properties, a two-step feeding method is advisable in the mixing process involving magnesium hydroxide; this approach yields better results compared to single-step feeding.