Interface engineering of multi-component core-shell flame retardant towards enhancing fire safety of thermoplastic polyurethane and mechanism investigation

Polymeric materials usually present substantial hazards to human health and the environment as a consequence of their flammability which leads to the emission of a great deal of heat and toxic fumes. To address this issue, it is imperative to urgently enhance the flame retardancy of polymer materials. This study focuses on the synthesis of a novel gel-silica/polydopamine double-layer microencapsulated cobalt ions (Co2+) modified ammonium polyphosphate (APP-Co@PDA@Si) and its utilization in thermoplastic polyurethane (TPU) composites. The resulting TPU composite, containing 10.0 wt% APP-Co@PDA@Si, exhibited excellent flame-retardant properties, i.e. achieving a limiting oxygen index of 30.0 % and the V-0 grade in the UL-94 test. Furthermore, peak heat release rate, total heat release, peak smoke production rate, and total smoke release of the TPU composite were decreased by 88.51 %, 66.06 %, 61.73 %, and 74.01 %, respectively, in comparison to those of pure TPU. The enhanced fire safety of the TPU composite was attributed to the synergistic effect among Co2+ catalytic carbonization, the free radicals capture effect of APP, and the flame-retardant functions of PDA and silane. This innovative strategy proposed in this work holds great promise for improving the fire-resistance of TPU.