Study On The Control Of Dielectric Properties Of SiO₂/Polyolefin Composites

With the rapid development of modern wireless communication technology,high speed,low loss and low delay of signal transmission in copper clad laminate substrates(CCL)are particularly important.However,the performance of CCL mainly depends on the performance of the dielectric substrate material.To meet the needs of industrial and advanced electronic devices,developing ceramic-polymer composites with low dielectric constant and dielectric loss is an effective way to reduce the size of electronic components and ensure signal quality.The high dielectric constant and high dielectric loss of traditional polymer resins limit its application in high-frequency CCL,while polyolefin resins have excellent dielectric properties and good processing properties.They have become ideal material for high-frequency CCL.In this study,three polyolefins,polybutadiene,ethylene-propylene copolymer and styrene-butadiene copolymer,are selected as the matrix resin,and SiO₂ is used as the filler.The SiO₂/polyolefin laminate composites were prepared by the method,and the influences of filler surface modification,initiator content and curing process on the composite system were discussed.The main contents and results of the research are as follows:(1)Study on the preparation process of SiO₂/polyolefin composites:The dispersion stability of fillers modified with different contents of KH-570 was tested,and the study found that the SiO₂ modified with 1.5 wt%KH-570 had the best dispersion;The 1,4-bis-tert-butylperoxy cumene(BIPB)and dicumyl peroxide(DCP)were used to cross-link the composite material,and the best type and dosage of initiator which is 3 pbw BIPB was obtained through performance testing and analysis.It is concluded that the optimal curing process is 175?/3 MPa/90 min through the performance analysis of the composite material under different hot pressing time and pressure.(2)Study on the influence of SiO₂ content on the properties of composite materials:A series of SiO₂/polyolefin laminate composites with different filler ratios were prepared by adding molten SiO₂ and crystalline SiO₂ as fillers,and their various properties were tested and characterized.The results show that with the increase of filler,the crosslink density,dielectric constant,loss and water absorption of the composites increase,and the thermal stability and mechanical properties also improve.The composite containing 70wt%molten SiO₂ has the highest tensile strength(22.85 MPa),lower dielectric loss(0.00279),and water absorption also kept at a low level(0.19%).performance.(3)Study on the effect of TiO₂/SiO₂ compound on the properties of composites:In order to further improve the dielectric properties of the composites,TiO₂/SiO₂/polyolefin composites were prepared by doping nanometer and micrometer TiO₂ with molten SiO₂respectively.When the doping content of nano-TiO₂ reaches 10 wt%(total filler content is 70 wt%),the composite exhibits the lowest dielectric loss(0.00217,10 GHz)and the highest tensile strength(24.69 MPa)and impact strength(4.138 KJ/m~2),and its water absorption remains below 0.2%.