Preparation Of Cyanate Ester-based Composites With Modified Fillers And Their Thermal And Dielectric Properties

With the high integration and miniaturization of electronic components,the effective heat dissipation of parts become crucial in microwave communication,electronic packaging,stealth materials and embedded capacitor fields.Cyanate ester resin(CE)features excellent chemical stability and dielectric property.In this paper,using thermally conductive hBN,MCMBs and their hybrid and surface modified forms repectively as fillers,a series of CE composites with improved thermal conductivity and dielectric property were made.Main studies are as follows:(1)The hBN/CE composites possessing the highest aspect ratio,crystallinity and widest particle size distribution shows highest thermal conductivity.Pre-ultrasonic exfoliation and surface-modification by WD60 and Z6020 coupling reagent improve the filler-matrix compatibility,hence increases composites' thermal conductivity and dielectric property.With the optimal content of 2.8 wt%,modified W-hBN/CE and Z-hBN/CE composites' thermal conductivity are 2.33 times and 3.05 times respectively of those unmodified.Spherical hBN filler was fabricated by spray drying process using polyvinyl pyrrolidone(PVP,K30)and Al(H2PO4)3 as binders.Sphercial hBN filled composite with K30 shows low delectreic constant and lower dielectric loss than those of CE resin.It is due to the low dielectric property of K30 and its good compatibility with CE matrix.(2)Spherical hybrid MgSiO3-SiO2-hBN fillers were fabricated by plasma synthesis process.The as fabricated fillers own good sphericity,and wide partice size distribution.The formation of thermal conductive network,perfect crystal structure and randomly distributed hBN particle in filler contribute to the high thermal conductivity of MgSiO3-SiO2-hBN/CE composite.With 35 vol%of filler content,MgSiO3-SiO2-52.1 wt%hBN/CE composite achieves the highest thermal conductivity(1.76 W/(m·K)),15 times higher than that of CE resin.The dielectric constant is about 4.5,and the dielectric loss is equal to that of CE resin.(3)As the formation of heat transfer network at mesocarbon microbeads(MCMBs)M22/CE composite with filling fraction of 40 vol%,composite achieves good comprehensive properties,including high thermal conductivity of 1.28 W/(m·K),low volume resistivity of 1.5 ?·cm,dielectric constant of 600(100 Hz),and dielectric loss<0.5,making it a promising material owning excellent conductivity of heat,conduvtive and energy storage.The thermal conductivity,electrical conductivity and the dielectic property of M22-CNTs/CE composite are improved by the synergistic effects of M22 and CNTs hybrid fillers.At CNTs content of 1.5 wt%,the composite obtains the highest thermal conductivity of 2.1 W/(m K),a low volume resistivity of 0.56?·cm,and an increased dielectric constant,26 times higher than that of composite without CNTs filler.(4)Spherical Ni@M22 powder prepared by pressurized hydrogen reduction process was modified by NDZ-201 coupling reagent.The presence of nickel shell together with the formation of electriacally conductive pathways improves the composite's thermal conductivity to 18%higher than that of composite filled with M22,and decreases the volume resistivity to 0.03 ?·m.The successful graft of NDZ-201 reduces the composite's resistivity to 10-3 ?·cm magnitude.When the content of coupling agent was 1.5 wt%,the corresponding composite presents the highest thermal conductivity of 2.1 W/(m K)and a high dielectric constant reaching up to 104 magnitude.