Study On Preparation And Properties Of BN/Epoxy Resin Composite

With the rapid increase of the density and power of electronic devices,the heat dissipation problem becomes a bigger problem hindering the development of electronic technology.Epoxy resin has been widely used in various fields,owing to its well-known properties,but its poor thermal conductivity limits its utiliza-tion in packaging field.Hexagonal boron nitride(h-BN),an important inorganic compound,can be used as filler to enhance the thermal conductivity of epoxy resin and contribute to solve the heat dissipation problem,due to its excellent properties,including thermal conductivity and stability.The aim of this thesis is to enhance the thermal conductivity of epoxy resin by filling surface-modified BN particles.The pristine h-BN powder was firstly treated with acetone,5M NaOH and annealing.The treatment effects were analyzed by SEM,FT-IR and XRD.Then,the modified h-BN powder was used as the thermal conductive filler to prepare BN/epoxy resin composite material.The thermal and dielectric properties were studied by means of thermal conductivity,thermal gravi-metric analysis and ?-? measurement.The effect of BN filler was also analyzed.FT-IR results show that after treating with 5M NaOH or annealed at 1000 ?,hydroxyl bond appears at the surface of BN particles,but the annealed BN particles exhibit better dispersibility by SEM analysis.BN nano-sheets were successfully obtained from annealed particles by centrifugal force,and well studied by TEM and Raman spectra.The results show that annealing treatment can exfoliate the ultrathin nano-sheet from the bulk BN,with the size of the ?m.And the thinnest BN layers were found to be only several atomic layers.The prepared BN nanosheets can effectively and stably dispersed in deionized water and ethanol and show obvious"Tyndall effect".The annealed BN powders were treated with silane coupling agent KH-550 at 60? for 2 h.The characteristic absorption peaks of functional groups of silane coupling agent appears in its FI-IR patterns,indicating silane coupling agent is chemically bonded to BN particles' surface.The curing temperature and curing time of epoxy resin are determined by the swelling method,that is,curing 3 h at 80 ?,and the epoxy resin matrix composites with different BN filling degree were prepared.With the increase of BN content,the thermal conductivity and stability of the composites are enhanced by the thermal conductivity test and thermogravimetric analysis.The thermal conductivity of the sample filled with 45 wt.%modified BN,compared to pure epoxy resin matrix,is enhanced by 46.8%.The BN/epoxy resin composites filled with modified BN powder exhibit better thermal conductivity and thermal stability than that of directly filled with pristine BN powder,which is attributed to the better link between filler and matrix and the presence of boron nitride nano thin layer.The prepared BN/epoxy resin composite material has excellent insu-lating property,and is qualified for application in the heat dissipation structure in electronic devices.