Effect Of Morphology And Particle Size Of SiO₂ On Dielectric Properties Of Polyolefin Composite Resin

In recent years,with the rapid development of modern information technology,electronic communication products have gradually developed toward light,short,high-frequency and high-speed.The dielectric properties of printed circuit boards greatly affect the signal propagation speed and efficiency.Substrate materials with excellent dielectric properties play an important role in the dielectric properties of printed circuit boards.Polyolefin resin with low dielectric constant and low dielectric loss is an ideal substrate material for high frequency printed circuit boards.Rogers of the United States has developed polyolefin composite substrate materials by adding a certain proportion of inorganic fillers to polyolefin resins.however,there are relatively few studies on polyolefin composite substrate materials in China.At the same time,studies have shown that the size and shape of inorganic fillers will have an impact on the overall performance of polymer matrix composites.Based on the above research background and development requirements,three polyolefin resins were selected as the matrix,and a low dielectric constant silica?SiO₂?was used as the inorganic filler.A series of SiO₂/polyolefin composites were prepared by changing the morphology and particle size of SiO₂.The effects of morphology and particle size of SiO₂ on the properties of composites were systematically investigated.The main results obtained from this paper are as follows:1.Using ethylene propylene diene monomer?EPDM?,polybutadiene?PB?,styrene-butadiene-styrene?SBS?as a resin matrix,and xylene as a solvent,the above resin and crosslinker 1,4-di-tert-butylperoxyisopropylbenzene?BIPB?and the antioxidant B225 were blended and cured.The experiment used atmospheric pressure high temperature curing to study the effect of the amount of crosslinker BIPB on the curing reaction.The analysis found that the optimal amount of BIPB was 3 phr.2.A series of SiO₂/polyolefin composite materials were prepared by adding amorphous SiO₂ and spherical SiO₂ as fillers to the above polyolefin composite resin.The mechanical properties,dielectric properties,water absorption and micromorphology of two kinds of SiO₂-filled composites were analyzed.The results show that compared with amorphous SiO₂,spherical SiO₂ has better interfacial interaction with resin matrix,better mechanical properties,and lower water absorption,dielectric constant and dielectric loss.3.A series of SiO₂/polyolefin composites were prepared by adding spherical SiO₂?20 nm,2?m,10?m?of three different particle sizes as fillers to the polyolefin composite resins.It is found that the mechanical properties of the composites are best when the content of nano-SiO₂ is 15 phr and the content of micro-SiO₂ is 10 phr.At the same content,the water absorption,dielectric constant and dielectric loss of the composite decrease with increasing SiO₂ particle size.