Use of High Phenyl‐Content Organosilicone and Ammonium Polyphosphate to Synergistically Enhance Flame‐Retardancy of Thermoplastic Polyurethane

ABSTRACT Thermoplastic polyurethane (TPU) is restricted in some applications due to its flammability, making flame retardant modification necessary. In this study, octaphenylcyclotetrasiloxane (P ₄ ) was utilized in conjunction with ammonium polyphosphate (APP) to modify TPU for flame retardancy. Experimental results showed that adding 3 wt% APP and 5 wt% P ₄ to TPU could achieve V‐0 level in the vertical burning test, and the limiting oxygen index significantly increased. Besides, smoke release and heat release were also obviously reduced. Additionally, the prepared P ₄ synergistic flame retardant TPU maintained good mechanical properties, far superior to those of TPU solely modified with APP. It was found that low additions of P ₄ could enhance the compatibility between APP and TPU, while higher P ₄ additions may lead to aggregation. Furthermore, scanning electron microscope, thermogravimetric analysis, thermogravimetry‐infrared, and energy dispersive X‐ray spectroscopy results revealed in detail the mechanism of P ₄ synergistically enhancing the flame‐retardant performance of APP‐modified TPU.