Preparation And Properties Of Metallocene PE/Graphite/Carbon Nanotube Conductive Composites Based On Mechanical Ball Milling

Organic resin raw materials have the advantages of high yield,low cost,chemical resistance,etc.,but most of the organic resins have poor conductivity,which limits their application in the field of electronics.If it can improve its electrical conductivity,it can replace some metals,and it can be applied in the fields of electronic components,electromechanical packaging materials and electromagnetic shielding materials,which will greatly enhance its economic value and development prospects.Metallocene PE is a modified polyethylene synthesized by metallocene(MAO)as a polymerization catalyst.It is a new type of thermoplastic material,which has better blending properties and tensile properties than ordinary PE.In this paper,graphite and carbon nanotubes pretreated by silane coupling agent are used as conductive fillers.Metallocene PE is used as the matrix of composite materials.The metallocene PE and conductive filler are ball-milled by self-made ball mill and prepared by hot press forming of flat vulcanizing machine.Metallocene PE/graphite/carbon nanotube conductive composite.Conductive composites with PE and metallocene PE as matrix were prepared,and their electrical conductivity,mechanical properties and electromagnetic shielding properties were studied.The main research contents are as follows:(1)The experiment first treats the graphite with a silane coupling agent,then places the pretreated graphite,multi-walled carbon nanotubes and PE in a ball mill,ball mills the material under certain conditions,and then places the mixed powder on the flat vulcanizing machine.Medium hot pressing.The effects of ball milling time,ball milling speed and ball milling temperature on the electrical conductivity of composites were investigated.The optimum process of PE/graphite/carbon nanotube conductive composites was discussed.The results show that the PE/graphite/carbon nanotube conductive composite prepared under the conditions of ball milling time of 60 min,ball milling speed of 150 r·min-1,ball milling temperature of 50 ? and hot pressing temperature of 185 ? and hot pressing for 15 min.The comprehensive performance of the material is the best.When the graphite is 20%by weight,the volume resistivity of the composite is reduced to 200 ?·cm.(2)The metallocene PE/graphite/carbon nanotube conductive composites were prepared by using metallocene PE as the matrix.The use of graphite and multi-walled carbon nanotubes as carbon-based fillers has good compatibility and synergy.Advantages As a conductive filler,a low filler high performance composite material is prepared.The experimental results show that when the addition amount of graphite is 15wt%and the addition amount of multi-wall carbon nanotubes is 5wt%,the electrical conductivity and mechanical properties of the composites are optimal.When the addition amount of the graphite is 15 wt%,when the content of the multi-walled carbon nanotubes is 5 wt%,the electrical resistivity of the metallocene PE/graphite/carbon nanotube composite decreases from 1.075x103 f2·cm to 1.36 ?·cm.It can effectively improve the electrical conductivity of the material.According to the literature,composite materials with conductivity of 1 ?·cm can be widely used in the field of electromagnetic shielding.(3)The study also found that the ball milling speed and graphite content have a great influence on the mechanical properties of the composite.When the ball milling time is 60 min,the ball milling speed is 150 r·min-1,the ball milling temperature is 50 ?,the graphite content is 15wt%,and the carbon nanotube addition amount is 5wt%,the conductive effect is excellent,and the tensile strength reaches 9.3 Mpa..(4)Synchronous thermal analysis of composite materials showed that the thermal decomposition temperature of metallocene PE/graphite/carbon nanotube conductive composite prepared by mechanical ball milling was 486.85 ?,which was higher than that of pure metallocene PE material of 481.84 ?,It is about 5 ?.The high melting point of the composite material is 94.25 ?,which is nearly 22.4 ? higher than the 71.85 ? of pure metallocene PE material.(5)SEM scanning electron microscopy analysis of metallocene PE/graphite/carbon nanotubes showed that the surface of metallocene PE was rougher after mechanical ball milling,and the specific surface area and diameter-thickness ratio increased,which was beneficial to improve the conductive filler.The dispersibility in the metallocene PE matrix facilitates the construction of the conductive pathways in the matrix.(6)Comparing with the MR050NAL type shielding material,it is found that when the thickness of the metallocene PE/graphite/MWCNTs conductive composite increases to 0.9 mm,the electromagnetic shielding effectiveness is 19 db,which is close to the MR050NAL type shielding material.Since the MR050NAL type shielding material uses foil as the base material,the metallocene PE/graphite/MWCNTs conductive composite is lower than the MR050NAL type shielding material in tensile strength,and the metallocene PE/graphite/MWCNTs is conductive in terms of elongation at break.The composite material is significantly better than the MR050NAL type shielding material.