Simultaneously improving the flame retardancy and toughness of epoxy composites with hyperbranched phosphorus-containing polysiloxane functionalized halloysite nanotubes

Development of high-performance thermosets with simultaneously improved flame retardancy, toughness and strength but unaffected glass transition temperature (Tg) has been a great challenge. In this work, hyperbranched phosphorus-containing polysiloxane functionalized halloysite nanotubes (HBPPSi-HNTs) were synthesized to prepare flame-retarding, mechanically-strong and tough epoxy composites. The tensile and impact strengths of the composites with 5.0phr HBPPSi-HNTs were improved by 23.7 % and 48.8 % respectively compared with the neat epoxy resin. The epoxy composites also exhibited excellent flame-retardancy due to the instantaneous gas -phase and condensed-phase flame retardant behavior of HBPPSi-HNTs. The composite with 10.0phr HBPPSi-HNTs passed UL-94V-0 rating, with an LOI value as high as 42.6 %. And compared with neat epoxy resin, the peak of heat release rate (PHRR), total heat release (THR), total smoke production (TSP) and CO generated per second (COY) were reduced by 50.1 %, 32.6 %, 30.1 % and 39.5 %, respectively. This work presented a general approach to prepare epoxy composites with simultaneously improved flame retardancy and mechanical prop-erties without sacrificing the glass transition temperature.