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To overcome the mechanical property compromises typically caused by reactive flame retardants while imparting excellent flame retardancy to epoxy resin (EP), this work designed a multifunctional phosphorus–silicon synergistic reactive flame retardant (PTSi). The aim was to achieve simultaneous enhancement of both flame retardancy and mechanical properties. The curing kinetics of the EP/PTSi system were studied using nonisothermal differential scanning calorimetry. Results revealed that adding only 1 wt % PTSi significantly reduced the activation energy of the curing process from 52.37 to 47.96 kJ/mol, thus accelerating the curing reaction. Furthermore, with a mere 2 wt % PTSi loading (PTSi-2), the cured product exhibited a notable increase in limiting oxygen index (LOI) from 22.6% to 28.5%, achieving UL-94 V-0 certification. Compared to pure EP, PTSi-2 reduced total heat release (THR) and total smoke production (TSP) by 25.3% and 43.1%, respectively, thereby enhancing fire safety. The high amino group content in PTSi promoted the uniform dispersion of phosphorus and silicon elements, while mitigating rigidity loss through increased cross-linking density, resulting in an 11.2% improvement in tensile strength for PTSi-1. Additionally, the incorporation of flexible Si–O segments led to an 86.3% improvement in impact strength. This study provides a promising strategy for developing reactive flame retardants that synergistically enhance both flame resistance and mechanical performance.
Dai et al. (Mon,) studied this question.