Thermoplastic polyurethane composite modified by piperazine pyrophosphate: Flame retardancy, thermal stability and combustion properties

In this work, flame retarded thermoplastic polyurethane (TPU) composites were fabricated by introducing a novel flame retardant piperazine pyrophosphate. The flame retardany, thermal stability and combustion performance were systematically investigated. Flame retardant tests confirmed that thermoplastic polyurethane/piperazine pyrophosphate (TPU/PAPP) composites showed LOI of 27.5 vol% without any melt dripping when only 5 wt% PAPP was added. micro-combustion calorimetry (MCC) test implied that PAPP significantly suppressed heat release of TPU/PAPP composites. 10 wt% of PAPP endow PHRR1 and THR values TPU/PAPP10 decreased by 67.0% and 35.1% compared with TPU. Thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) showed that PAPP significantly inhibited the release of toxic and combustible gases. The char residue investigation showed that TPU/PAPP composites formed compact char residue, which was able to effectively inhibit the heat and mass transmission in combustion. Based on the investigation, the work mechanism of PAPP in TPU/PAPP composites was proposed.