Enhanced Flame Retardancy of Polyethylene Composites Through the Development of an Efficient System Comprising Magnesium Hydroxide/ MQ Silicone Resin/Calcium Borate

ABSTRACT The excellent flame retardancy and low smoke emission of polyethylene (PE) composites were crucial for the wire, cable, and automotive plastics industries. In this work, magnesium hydroxide (MH) was modified with MQ silicone resin (MQ) to create a flame‐retardant MH/MQ, which was subsequently combined with calcium borate (CaBO) to develop a comprehensive flame‐retardant system. With a total addition of only 30 wt.%, the PE/MH/MQ@CaBO (70/28/2) composite achieved a limiting oxygen index (LOI) of 27.1 vol.%, representing a 55.7% increase compared to pure PE. Additionally, it demonstrated exceptional fire safety performance, with the peak heat release rate (PHRR) reduced by 31.5% to 266 kW/m and total smoke production (TSP600s) decreased by 27% to 3.5 m2. The dispersion of MH/MQ within PE was significantly improved due to the unique structure of MQ. Furthermore, the combination of MH/MQ and CaBO exhibited synergistic effects in improving flame retardancy and smoke suppression. The results demonstrate that the flame retardant mechanism primarily functions in the condensed phase through a continuous, dense char layer, which restricts heat and mass transfer during combustion.