Fire, thermal and mechanical properties of TPE composites with systems containing piperazine pyrophosphate (PAPP), melamine phosphate (MPP) and titanium dioxide (TiO2)

A novel synergistic flame retardant system containing piperazine pyrophosphate (PAPP) synthesised by polycondensation, melamine phosphate (MPP) and titanium dioxide (TiO2) was applied to the thermoplastic elastomer (TPE). The char residues of TPE/PAPP/MPP/TiO2 composites were 23.5 wt-% in N2 and 17.3 wt-% in air. Meanwhile, the as-obtained composites showed enhanced flame retarding properties including high limit oxygen index (LOI) valuing (37.8 vol.-%) and UL-94 V-0 rating. TGA results indicated that the fire retardant systems significantly altered the initial decomposition temperature (5-20°C) and resulted in the formation of increased residues (23.5 wt-% in N2 and 17.36 wt-% in air). In addition, the scanning electron microscope (SEM) test and gas analysis proved that char formation was significantly accelerated in this system. Non-combustible gases like ammonia and carbon dioxide could dilute the concentration of combustible gas, and result in the fuel reduction action as the minor. The heat and smoke release behaviours were also measured by cone calorimeter. The tensile strength, elongation at break and notch impact strength of the FR-TPE composite increased by further substituting a portion of the PAPP with MPP and TiO2. The flame retarding mechanism of this system was also studied by SEM-EDX.