Flame Retardancy and <scp>UV</scp> Resistance of Polysiloxane‐Modified <scp>APP</scp> and <scp>THEIC</scp> in <scp>LDPE</scp>

ABSTRACT Low‐density polyethylene (LDPE) has emerged as a crucial plastic material due to its excellent processability and broad range of applications. However, its inherent low flame retardancy and vulnerability to aging restrict its use in certain fields. Consequently, enhancing the flame retardancy and UV resistance of LDPE has become a focus in current research. In this study, we adopted a stepwise approach to develop flame retardants with UV resistance. First, ammonium polyphosphate (APP) was modified with polysiloxane to improve its thermal stability and flame‐retardant properties. Then, the modified APP was combined synergistically with THEIC in preparing LDPE. This method enhances compatibility among different components, thereby optimizing the overall performance of the material. Experimental results reveal that LDPE containing modified APP and THEIC exhibits excellent flame‐retardant and mechanical properties. Specifically, the material's oxygen index increased to 31.0%, while total heat release and total smoke release decreased by 75% and 59.5%, respectively, compared to untreated LDPE. Regarding UV resistance, after 100 h of UV exposure, the oxygen index showed minimal change, and the material maintained a UL‐94 V‐0 rating. Additionally, tensile strength and elongation at break only decreased by 0.76% and 6.9%, respectively, highlighting its impressive UV resistance.