Tertiary nitrogen carbonization and imine cross‐linking facilitated solid‐phase flame retardant for anti‐dripping PA6 fiber

Abstract A developing society requires polycaprolactam (PA6) fibers with flame retardant. Currently, the additive flame retardants commonly used in PA6 fibers cannot solve the molten droplet problem. In this work, (1 E ,1 ′ E )‐ N , N′ ‐(6‐phenyl‐1,3,5‐triazine‐2,4‐diyl) bis (1‐(4‐methoxyphenyl) methanimine) (NBM) with triazine ring structure was synthesized. The triazine ring structure was used to expand into carbon and benzoguanimine structure to produce irreversible chemical crosslinking in NBM, thereby achieving anti‐dripping and flame retardant of PA6 fiber. LOI of PA6/NBM 8 reaches 30.0 vol.%, UL‐94 reaches V‐0 when the NBM addition amount is 8 wt.%, meanwhile, the residual carbon content is 235.7% higher than that of PA6. The mechanical strength can still reach to 3.22 cN/dTex. From structural design to synthesis, the effects of NBM addition on the flame retardants, rheology, thermal stability and residual carbon morphology of PA6/NBM x were analyzed in detail in this work. It is hoped that in the future work, the structural characteristics and performance requirements can be matched to provide reference for conception and synthesis of flame retardants oriented to other polymers.