Study On Properties Of Hyperbranched Polyester Modified Nano-barium Titanate/Epoxy Composites

To further improve the energy storage characteristics of energy storage devices,there is an urgent need for high dielectric constant materials with excellent overall performance and easy processing.At present,high dielectric composite materials made of barium titanate as a filler and epoxy resin as a matrix are common.Due to its high dielectric loss and weak resistance to breakdown,it seriously affects its service life and applicable field.In this paper,BaTiO3 was modified with a coupling agent and a hyperbranched polyester synergistic coupling agent,and mixed with epoxy resin to make a composite material.Then the effects of BaTiO3 content and modification methods on the electrical properties and thermal conductivity of BaTiO3/EP composites were studied.First,the surface modification of BaTiO3 powder was carried out by two modification methods,and the Fourier infrared spectrum was observed to compare the changes of functional groups before and after modification,proving that the hyperbranched polyester has been successfully grafted on the surface of BaTiO3.Then,prepare BaTiO3/EP composite material,observe the SEM images of the two modification methods,analyze the influence of the hyperbranched polyester modification on the distribution characteristics of the filler in the composite material,and learn that the hyperbranched modification method can further improve the compatibility between BaTiO3 and the epoxy body,improve the dispersibility,and improve the aggregation defects.The macro-performance test results show that the dielectric constant of the hyperbranched modified BaTiO3/EP composite has been significantly improved,reaching a peak of 37.1 at a frequency of 1 kHz and a mass fraction of 60 wt%.Although the dielectric constant of the coupling agent modification method has been reduced by 10%compared with that under the same conditions,its dielectric loss has been greatly improved by 31%,thus increasing the service life of the material to some extent.At the same content of 60%,the partial discharge starting voltage and AC breakdown field strength were improved by 13%and 22.7%respectively compared with the coupling agent modification method,which improved the insulation performance.The thermal conductivity reaches the highest value of 0.383 W/(m·k)when the filling amount is the highest,which is 31%higher than that of BaTiO3/EP composite modified by the same mass fraction coupling agent,which is beneficial to reduce thermal aging.In summary,the surface of BaTiO3 modified by hyperbranched polyester synergistic coupling agent has a large number of long-chain molecules,which can further expand the agglomerates and improve the dispersion.Also,BaTiO3 and epoxy groups are tightly connected with more covalent bonds,the interface effect is enhanced,and then the overall performance of the material is improved.