The silicone thermoplastic elastomer is highly attractive in various areas for good mechanical strength and aging resistance. However, its intrinsically high flammability limits its practical applications. Meanwhile, as a typical polymer material, its irreversible cross-linking structure makes it difficult to recycle and reprocess; a great deal of discarded silicone materials can pose a waste of resources and environmental problems. Herein, it is of great significance to prepare an intrinsic flame retardant (FR) and reprocessable silicone polyurethane (STPU). In this study, we introduce phosphorus-containing compounds (MDP) and a dynamic phenylborate ester (HDPM) bond into traditional silicone’s molecular chain structure by in situ polymerization method, which endows the material with excellent flame retardance and reprocessing properties, respectively. The resultinf STPU shows a limited oxygen index (LOI) value of 26.1% and reaches at VTM-0 rating. Furthermore, by regulating the decomposition and reconstruction of the phenylborate ester structure, STPU remain the initial tensile strength and keep 87.58% of tensile strain after twice reprocessing. This high-performance sustainable STPU materials hold great promise for fire safety behavior and reutilization in practical application.

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Linear low‐density polyethylene (LLDPE) combined with the piperazine pyrophosphate (PAPP) and melamine cyanurate (MCA) was adopted to prepare the flame retardant LLDPE composite by melt blending. The research results showed that the PAPP/MCA mixture with a mass ratio of 4:1 presented the optimal flame retardant effect. With the 25 wt% addition amount, the LLDPE composite passed the UL‐94 V‐0 level (1.6 mm), and the limiting oxygen index (LOI) reached 29.4%. The peak of heat release rate (PHRR) decreased by 78.9% from 877.5 to 185.0 kW/m2, which is attributed to the good synergistic effect between PAPP and MCA, forming the stable and compact char layer. Besides, the thermal behaviors were characterized through thermogravimetric (TG) analysis, and the synergistic mechanism was investigated by scanning electron microscopy (SEM), TG analysis‐infrared spectrometry (TG‐IR), and x‐ray photoelectron spectroscopy (XPS). The results indicate that the good synergistic flame retardant effect can enhance the flame retardancy of LLDPE materials, and with the addition of MCA and PAPP, a flame retardant LLDPE composite with good thermal stability and mechanical properties can be prepared with no molten droplets on combustion, which provides a feasible solution for the application of high‐performance halogen‐free flame retardant LLDPE materials.