A phosphorus/silicon-based, hyperbranched polymer for high-performance, fire-safe, transparent epoxy resins

The implementation of current flame-retardant strategy is often accompanied by the deterioration of other properties, e.g., mechanical and optical properties. Herein, a flame-retardant, hyperbranched polymer was synthesized by using trichlorovinylsilane (TVS), triethylenetetramine (TETA) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as raw materials, which was named as TTD and applied to epoxy resin (EP). Our result shows that TTD is able to catalyze and participate in the curing of EP. Furthermore, the EP-TTD samples exhibit high transparency, glass-transition temperature and good UV-blocking properties at a low TTD addition (<= 4 wt%). Notably, TTD enhances the toughness and robustness of EP. The elongation at break, tensile strength, flexural strength, and impact strength of EP containing 4 wt% TTD are 54%, 42%, 29%, and 29% higher than those of pure EP. Meanwhile, the incorporation of 7 wt% TTD endows EP with a limiting oxygen index (LOI) of 40.0%, a UL-94 V-0 rating, and a 13% reduction in total smoke production (TSP), indicating the significantly enhanced fire safety. During burning, TTD exerts promoting carbonization and quenching effects to suppress the heat transfer and smoke release. Therefore, this work provides an effective strategy to fabricate high-performance, fire-safe epoxy resins using P/Si-containing, hyperbranched polymers.