Fascinating flame resistance of polycaprolactam copolymer containing d‐glucopyranose for melt‐spun flame retardant fibers

Improving the flame retardant performance of polycaprolactam (PA6) will greatly expand its applications. At present, the commonly used reactive flame retardants of PA6 mainly come from the petrochemical industry. Therefore, d‐glucopyranose, a green renewable biomass, is selected and bonded to the PA6 molecular chain through in situ polymerization to obtain a series of flame retardant polyamides (PA6/Gl) and their high‐speed melt‐spun fibers. When its added amount was 2 wt%, the LOI and UL‐94 of PA6/Gl reached 29.4 Vol% and V‐0 level, and the char residue was 529.4% higher than that of neat PA6 after thermogravimetric test. d‐glucopyranose contains a polyhydroxy structure that can capture the hydrogen radicals generated by homogeneous cracking during combustion, increasing the content of CO2 and H2O and forming a smooth and dense carbon isolation layer. Thus, the synergistic flame retardant effect of green d‐glucopyranose on the gas and condensed phases of PA6 is achieved. d‐glucopyranose, a green renewable material, was added to the polycaprolactam (PA6) molecular chain by in situ polymerization to obtain melt‐spun flame retardant fiber. It provides a new strategy for bio‐based materials as flame retardants through the synergistic flame retardant mechanism of gas and condensed phases.