Different flame retardancy effects and mechanisms of aluminium phosphinate in PPO, TPU and PP

Based on the thermal degradation behaviour and the char residue of these composites, the flame retardancy mechanisms of the three systems were discussed. For AlPi/PPO composites, the flame retardancy mechanism was condensed phase charring mechanism because of the formation of continuous char layer during combustion. For AlPi/TPU composites, AlPi acted mainly in gas phase, and a synergistic reaction of phosphorus and nitrogen compounds occurred and diethylphosphic acid providing flame inhibition was released during the burning process. As a result, the addition of AlPi successfully reduced the melt-dripping and enhanced flame retardancy of TPU matrix. For AlPi/PP composites, AlPi acted as a flame inhibitor in gas phase, decreasing the effective heat of combustion of the volatiles (THE/TML) and increasing the amount of CO.