Impact of diisobutyl aluminum hypophosphite on flame‐retarded thermoplastic polyester elastomers composites and its mechanism

Abstract Thermoplastic polyester elastomer (TPEE) is widely used in industries such as healthcare, electronics and electrical appliances, wire and cable sheathing, and automobiles due to its excellent comprehensive properties. However, the extreme flammability significantly restricts its practical applications and further development. To address this issue, an additive, aluminum diisobutylaluminium hypophosphite (APBA), was introduced into TPEE as the flame retardant. The results showed that the limiting oxygen index (LOI) of the TPEE composite with 17.5 wt% APBA was increased from 17.5% (pure TPEE) to 33.8%, and the corresponding vertical combustion grade (UL‐94) reached V‐0 level. In addition, the TPEE/APBA composite materials exhibit relatively good mechanical and electrical insulation properties. The tensile strength was maintained at 10.57 MPa, and volume resistivity increased by 491.47%. According to the result of the gas–solid phase products analysis of the composite, the quenching effect of phosphorus‐containing free radicals resulting from APBA was confirmed. Meanwhile, the addition of APBA promoted the formation of a stable, dense, and smooth carbon layer composed of aluminum‐containing polyphosphate and graphite structure, thus isolating the oxygen and heat transfer. Highlights TPEE/APBA (17.5 wt%) composite achieved a UL‐94 V‐0 rating with a high LOI of 33.8%. APBA played dual functions in gas and condensed phases as a flame retardant for TPEE. The flame‐retardant mechanism of TPEE/APBA was elucidated.