“…Because of its low density, versatility, easy processing, good performance-to-cost ratio, and good mechanical properties, polypropylene (PP) has been widely used in many fields, including automobiles, building materials, electronics, and electric materials. [1][2][3] However, because of a large number of methyl groups, PP is easily ignited with a fast fire spread speed, and it can produce large amounts of toxic gases during combustion; these gases threaten the safety of human life and restrict PP's use in high-risk applications. [4][5][6] Thus, it is necessary to improve the fire safety of PP, and various attempts have been made to reduce its flammability through the introduction of various flame retardants (FRs) into PP.…”