Research On Thermal Conductivity And Mechanical Properties Of High-filling Polyethylene-based Composites

With the development of the electronic industry,the integration of the product and the concentration of assembly are increasing,and the performance requirements of the materials are more and more high.It also requires good mechanical properties and other properties for different occasions.The traditional metal material is difficult to process and is easily to be corroded,and the metal density is very high.This reasons restrict its use range.However the polymer-based composites have the advantages of low density,good corrosion resistance,convenient porcessing,and low cost,so it is a hot point to study the polymer-based composites.The paper studies the preparation of high-fill polyethylene-based materials with high thermal conductivities.The materials is based on polyethylene,which is made of grapihite and boron nitride as thermal fillers.The research content is as follow:Graphite was selected as high thermal conductivity filler,and modified by hot sintering method.A nickel coating,a silicon layer,and a silica nanowires grew on the surface of the garphhite respectively.Then the modified graphite powder and the unmodified graphite powder separately were taken to combine with the low density polyethylene to prepare the composites.The effects of the preparation method,the content of filler and the modification of the filler on the perfomaces of the composites were studied.The result showed that(1)with the test of XRD?SEM?EDS?XPS desmontrate that the graphite surface was modified.A nickel coating,a silicon layer,and a silica nanowires were growed separately on the surface of the garphhite.(2)the thermal conductivity of composite materials increased with the increase of the contents.Compared with the thermal conductivities of four kinds of composite materials,its value presented the following laws: when adding the same amount of fillers,the improvement of the fiilers for the thermal conductivity of composite was in turn,unmodified graphite > nickel plating graphite> silicon plating graphite> siclica plating graphite.The high thermal conductivity low density polyethylene-basedcomposites showed good thermal performance under the self made heating device.(3)Compared with low density polyethylene-based composite filled with graphite,filled with nickel plating graphite and silicon plating graphite,we tested the mechanical properties of materials by a universal test machine.Its value presented the following laws: when adding the same amount of fillers,the improvement of the fiilers for the bend strength of composite was in turn,nickel plating graphite> silicon plating graphite>unmodified graphite.(4)the experiment results of lose-wight analysis showed that with the addition of graphite filler,the thermal stability had increased.The polyethylene-based composites with high thermal conductivity and electrical insulating filled with boron nitride powder were prepared by vacuun hot press sintering.And the effect factors on the particle size,the content of boron nitride powder and different porcess methods were discussed.The relationship between thermal model and thermal conductivity of ultra-high molecular wight polyethylene-based composites was also studied.The result showed that(1)the preparation process had effectively improved the dispersion of thermal conductivity fillers in the composites.The thermal conductivity of composite materials increased with the increase of the contents of boron nitride powders.The thermal conductivity of composite filled with large size fillers was better than that filled with small size.When the filling reached 60vol%,the X-Y thermal conductivity of the composite was14.813W/mK,46 times higher than the polymer matrix.(2)the mechanical properties of composite materials reduced with the increase of the contents.We tested the mechanical properties of materials by a universal test machine.Its value presented the following laws: The addition of a certain amount of filler boron nitride improved the mechanical properties of the polymer.When adding the same amount of fillers,the improvement of the fiilers for the bend strength of composite was in turn,20?m BN powder>50?m BN powder.(3)using the common classical Maxwel-Eucken model and Hatta-Taya model to simulate the theraml conductivity of the composite material.The results showed that the Maxwel-Eucken equation was not adaptable for the experiment datas.In the Hatta-Taya model,the experiment datas of the X-Y thermal conductivity of composite filled with 20?m BN was consistent with the prediction.The experiment datas of the X-Y thermal conductivity of composite filled with 50?m BN was not consistent with the prediction,greater than the predicition.