Enhancing toughness, flame retardant, hydrophobic and dielectric properties of epoxy resin by incorporating multifunctional additive containing phosphorus/silicon

•A phosphorus/silica synergistic multifunctional epoxy additive (ETP) was synthesized.•ETP shows excellent flame-retardant and smoke-suppressant performances.•The toughness of the cured product increased by 114 % with the addition of 6 wt% ETP.•6 wt% ETP improves the dielectric and hydrophobic properties by more than 40 %.