Preparation And Properties Of Ball Milling Graphite/polyethylene Composites

With the continuous development of society,heat exchangers,floor heating pipes and other fields have put forward higher requirements for thermally conductive materials.Comprehensive thermal conductive materials with characteristics of corrosion resistance,low cost,easy processing and good mechanical properties have become the development direction of thermal conductive materials.Polyethylene(PE)is an important thermoplastic resin with excellent comprehensive properties,but its low thermal conductivity limits its application in the field of thermal conductivity.In order to prepare heat conducting polymer materials with good mechanical properties,so as to expand the application of polymer materials in the field of heat conduction.It is an effective method to prepare thermal conductive polymer composites by adding high thermal conductive fillers to the polymer matrix.In this paper,polyethylene-based composites with low filling and high thermal conductivity were prepared by melt blending method after graphite was modified by mechanical ball milling.In this experiment,through the mechanochemical action of planetary ball mill,two kinds of small molecules containing nitrogen atoms,urea and stearamine,were used as stripping agents to modify graphite by ball milling.Orthogonal experiments were used to prepare exfoliated graphite platelets(EGP)under different experimental conditions.EGP was melt-blended with polyethylene(PE)to prepare PE/EGP composites with different EGP contents.The morphology,structure and composition of EGP were characterized by SEM,XRD,FTIR,TGA and Raman.The thermal conductivity,mechanical properties,rheological properties,thermal properties and cross-section morphology of the PE/EGP composite were characterized.The EGP prepared by the two kinds of stripping systems has obvious surface modification and exfoliation compared with the original graphite.The EGP prepared by the two systems has significant improvement on the thermal conductivity and tensile strength of PE,and the EGP prepared by octadecylamine has better improvement on the thermal conductivity and tensile strength of PE than by the urea system.Especially when the EGP was prepared by ball milling for 5 hours with octadecylamine as stripping agent,the filling amount of EGP in the composite was 10wt%,the highest thermal conductivity of the composite is 1.2132 W/(m?K),which is 3.01 times than that of PE.Meanwhile,the highest tensile strength of the composite is 21.74 MPa,which is 1.38 times higher than that of pure PE,and the elongation at break of the composites was 765%.Therefore the PE/EGP composites prepared in this experiment have good mechanical properties and high thermal conductivity,which is expected to be applied in fields of heat exchange equipment and electronic packaging.