Study On Preparation And Dielectric Properties Of Exopy Composites Filled With Passivated Zinc Sheet Powders

To realize the miniature and high-speed of electrical devices and components,embedded passivese with high dielectric constant and low loss have received closeattention from both academic and industrial circles. As a promising dielectric medium,metal particles fillers/polymer composites have been suggested to apply in embeddedpassivese, because of their high dielectric constant and low cost. But an intractableproblem is the high loss tangent included in these materials. To overcome it, in presentpaper, we design a composite consisting of passivated zinc sheet powders and epoxy resin,the processing routine involved and dielectric properties were studied, the main results areas follows:Zinc sheet powders were passivated by two solutions H2O/alcohol and H2O2/H2O.SEM analysis shows swell-like Zn(OH)2microstructure grows on the surface of zinc sheets,the surface passivated by H2O2/H2O was more rough than that passivated byH2O/alcohol.The passivations of zinc sheets increase with time and the concentration ofoxidant,the weight gain rate showed a liner relationship with the thickness gain rate.Withthe increase of the thickness of the passivation film,electrical resistivity of zinc powdersdisc increases, and the corresponding leakage current density descends.When the mass ratio of epoxy resin TDE-85to curing agent MeHHPA is close to1:1.43, the curing degree of resin system reaches the maximum value97.88%. Thecorresponding reaction activation energy of resin system is67.323kJ/mol with a reactionorder of about0.9. From TG analysis, the curing routine is recommended as follows:110℃/3h+130℃/3h+150℃/4h.Dielectric measurements show both dielectric constant (ε) and dielectric loss (tanδ) ofthe composites increase with the the content of zinc powders. The composite filled withzinc sheets with a7%passivation weight increase (PWI) has a ε=46.35and tanδ=0.026at aloading volume fraction of φ=25%, comparatively, the one filled with zinc sheets with a21%PWI has a ε=33and tanδ=0.016at φ=25%. In addition, with the increase of thefrequency, dielectric constant of composites has a slight decline while the dielectric losshas an increasing trend at a rather low level. The reason is attributed to the fact that the kinematic units in composites cannot follow AC electrical field applied in high frequency,then the polarization recede, leading to the decrease of dielectric constant.