Flame‐retardant polyamide 56 with high fire safety and good thermal performance

Abstract

AbstractAs a recently developed biobased polyamide, polyamide 56 (PA56) has great potential in the field of fibers and textiles due to its high strength, high moisture absorption, and easy dyeing. However, the application of PA56 is restricted due to its flammability. Flame‐retardant PA56 copolymers (FRPA56s) have been designed and successfully synthesized by the introduction of 2‐carboxyethyl(phenyl)phosphinic acid (CEPPA) monomer. The thermal properties and thermal stability of FRPA56s have been evaluated using DSC and TGA, respectively. The flammability behavior of the resultant copolymer has been investigated using UL94 vertical burning and cone calorimetry tests. The crystallization temperature (Tc), melting temperature (Tm), and crystallinity (Xc) of FRPA56s are reduced and the degradation pathway for PA56 is changed with the introduction of CEPPA. In addition, FRPA56 containing 7.8 mol% CEPPA may be characterized by a V‐0 rating in the UL94 vertical burning test and its total heat release is reduced 20% than that of PA56, reflecting the high flame‐retardant efficiency of CEPPA. Based on the analysis of the residual char and the gas‐phase pyrolysis products for combustion of FRPA56s, it is concluded that the flame‐retardant modes of action for this material mainly include flame inhibition, dilution effect and charring.