Fabrication and fire safety performance of discarded bamboo chopsticks-derived biomass intumescent flame retardant in thermoplastic polyurethane composites

In this study, the carbon-rich cellulose architecture derived from discarded bamboo chopsticks was successfully valorized as a sustainable bio-carbon source, completely replacing traditional petroleum-based pentaerythritol (PER), to produce an intumescent flame retardant. A biomass-based intumescent flame retardant thermoplastic TPU composite material with P/N synergistic effects was prepared and compared with a conventional intumescent flame retardant, namely a PER/melamine (MEL)/ammonium polyphosphate (APP) composite. The biomass-based composite exhibited superior flame retardancy, smoke suppression, and toxicity reduction effects compared with the PER-based composite. Specifically, the TPU composite incorporating 30 wt% of the bamboo/MEL/APP intumescent system exhibited an elevated limiting oxygen index (LOI) of 29%, surpassing the 26% observed in the TPU/PER/MEL/APP system at the same loading. In addition, the biomass-derived formulation achieved a UL-94 vertical rating improvement from failure to V-0. The peak heat release rate, total heat release, and total smoke output were reduced by 45.18%, 37.98%, and 37.68%, respectively.