Effects Of Particle Size And Concentration Of TiO₂ On The Dielectric Properties Of Polyolefin Composite Resins

With the advent of highly information-oriented era,electronic components have been developing towards the direction of high frequency,miniaturization and high integration,which puts forward higher demands on the dielectric,thermal and water absorption properties of substrate materials.Dielectric properties are significant properties of substrate material,which greatly affect the size of electronic components and signal propagation loss.Polyolefin resins are ideal materials for microwave substrates on account of their stable dielectric properties,excellent processing performance and comprehensive properties.Incorporating inorganic fillers into polyolefin resins is an effective approach to improve their dielectric properties and thermal properties,and researches show that the content and particle size of fillers will affect the properties of composites.The composite dielectric substrate developed by Rogers of the United States,which is based on polyolefin resin and reinforced with inorganic filler,is widely favored for its excellent performance.However,the researches on such products are relatively few in China,so the study of polyolefin-based high frequency composite substrates is of great significance.In this paper,polyolefin/TiO₂/GF composite substrates were prepared by impregnation and hot pressing with polybutadiene?PB?,styrene-butadiene-styrene triblock copolymer?SBS?,ethylene-propylene-diene terpolymer?EPDM?composite resin as matrix,glass fiber as reinforcement material,and titanium dioxide?TiO₂?with high dielectric constant as inorganic filler.First,the surface modification of fillers and the preparation technology of composite substrates were studied.Then,the effects of concentration and particle size of TiO₂ on the performance of composite substrates were investigated systematically.Finally,the influence of TiO₂ with different particle size distribution on the properties of composite substrates was researched.The main contents and results are as follows:1.Study on preparation technology of composite substrates:The surface modification effect of fillers was analyzed,and the solvent amount as well as the hot pressing process of substrates were explored.?a?The compatibility of TiO₂ with organic phase was improved after the modification of TiO₂ with 1.5 wt%KH-570.?b?When the ratio of filler to solvent was 1:1,and the ratio of other raw materials to solvent was 1:2,the glue flow phenomenon was inhibited and the composite substrates properties were enhanced.?c?The curing reaction temperature was determined by DSC analysis,and the influence of thermal pressure on the performance of substrates was investigated.The optimum hot pressing process is 180/5 MPa/1 h+250/5 MPa/1 h.2.Research on the effects of concentration and particle size of TiO₂ on the performance of composite substrates:?a?With the increase of TiO₂ content,the dielectric properties,thermal stability and mechanical properties of the substrates were enhanced,and the water absorption increased.70 wt%TiO₂ was an optimum choice.?b?With the decrease of particle size,the dielectric,mechanical properties of the substrate were enhanced,the water absorption increased,and the thermal properties were basically stable.Substrate with 230nm TiO₂ possesses the best properties.3.Investigation on the influence of TiO₂ with different particle size distribution on the properties of composite substrates:TiO₂ with particle sizes of 60 nm and 230 nm were compounded,and substrates had superior performance after filler compounding.With the increase of the ratio of small size TiO₂,the coefficient of thermal expansion and temperature drift of the substrates decreased,the dielectric and mechanical properties enhanced,and water absorption increased.When the ratio of small size TiO₂ was 30 wt%,the substrate had the best performance.