A novel inherently flame-retardant thermoplastic polyamide elastomer

Abstract

Thermoplastic polyamide elastomers (TPAEs) are a new and important member of the thermoplastic polymer elastomers (TPEs) family, and the flame retardation of TPAEs is a big challenge due to the deterioration of their properties. In this work, we have successfully designed and synthesized the first “inherently” flame-retardant TPAE by introducing a phosphorus-containing group (DDP) into the macromolecular chains through P-C covalent bonds. The properties of TPAEs can be regulated by controlling the contents and distribution of polyamide (PA) segments as a hard segment, polyethylene glycol (PEG) as a soft segment, and DDP as a flame retardant unit during the synthetic process. The resulting TPAEs can achieve a V-0 rating in the UL-94 test and a limiting oxygen index of higher than 35.0%. The enhancement of flame retardancy is attributed to the droplet-promoting mechanism and the free radical quenching effect in the vapor phase. Unfortunately, the density of the inter-chain H-bonding and crystallinity of the PA segments regions decreased with the incorporation of DDP groups, which lead to the decrease of the tensile properties of TPAEs. However, the samples with high flame retardancy are still able to maintain 400% of elongation at break and 20 MPa of tensile strength, respectively, which have better comprehensive properties than typical commercial TPEs (Pebax®). Therefore, this novel inherently flame-retardant thermoplastic polyamide elastomer will exhibit a wider range of application potentials.