Improved mechanical and flame retardant properties of vinyl ester resin composites by combination of lithium-containing polyhedral oligomeric phenyl sesquisiloxanes and phosphorus-containing ionic liquid

Vinyl ester resin (VER) are widely used in various applications, including automotive parts, yachts, wind turbine blades, and cooling towers, due to their excellent properties. However, the high flammability of VER limits its application in fields requiring stringent fire resistance. In this work, we used ionic liquid containing phospholipid structures (VIDHP) in combination with lithium-containing polyhedral oligomeric phenyl sesquisiloxanes (Li-POSS) to improve the mechanical and flame retardant properties of VER. The coordination between the VIDHP and Li-POSS increases the thermal stability of VIDHP and improve the solubility of Li-POSS in VER. The experimental results show an increase in initial decomposition temperature of VIDHP4/POSS1/VER compared to VIDHP/VER, while the solubility of Li-POSS in VER is improved. The Cone calorimeter results show that the total heat and smoke release of VIDHP4/POSS1/VER are reduced by 29.37 % and 36.55 % compared with the pure VER. The investigation of the flame retardant mechanism shows that the combined use of VIDHP and Li-POSS exhibits flame-retardant activity in both the gas and condensed phases, effectively enhancing the flame-retardant property of VER.