To obtain high dielectric constant materials with low loss

good breakdown and thermal conductivity

BaTiO

3

was modified with a hyperbranched polyester synergistic coupling agent

and epoxy resin was used as the matrix to fabricate a composite material. The dielectric properties

breakdown properties and thermal conductivity of composites under different loadings and different modification methods were compared and studied. Microscopic analysis shows that the hyperbranched modification of BaTiO

3

can improve its dispersibility and compatibility in EP

and can modify the agglomeration defects. Moreover

the dielectric constant of the hyperbranched BaTiO

3

/EP composites can be significantly improved

reaching 37.1 when frequency is 1 k Hz and mass fraction of BaTiO

3

（ω（BaTiO

3

）） is 60%. The dielectric constant of the BaTiO

3

/EP composite modified by the coupling agent is decreased by 10%

whereas

its dielectric loss angle tangent is decreased by 31%. When ω（Ba Ti O3）=60%

its AC breakdown field strength is 22.7% higher than that of coupling agent modified BaTiO

3

/EP composites. The thermal conductivity reaches the highest 0.383 W/（m·K） when ω（Ba Ti O3） is 60%

which is 31% higher than that by the modification method of coupling agent with the same mass fraction. The above results show that BaTiO

3

modified by the hyperbranched polyester synergistic coupling agent can enhance the interface effect

weaken the interface polarization

reduce the charge mobility

and improve the comprehensive properties of the composite.