Research On Compounding Methods Of Graphene And Polyolefins And Modification Effect On Polyolefins

Polyolefins are widely used in life and industry due to its low cost, easy processing and excellent allround properties. However, there are still some shortcomings in their some properties, such as low strength, poor dimensional stability and unsuited for anti-static applications. To improve performance and broaden application areas, polyolefins should be modified. Graphene is a new two-dimensional carbon nanomaterial with excellent mechanical,electrical and thermal properties, which has good application prospect in modification of polyolefins.The present research mainly focuses on the modification of polyolefins by means of solution blending with modified graphene. But this technique has some drawbacks, for example, tedious modified process, environmentally unfriendly and unsuitable for large-scale production. So we attempt to take compounding methods as a cut-in point. This thesis focuses on compounding methods and modification effect on polyolefins, using multi-layer graphene prepared by mechanical exfoliation and HDPE as raw materials. In order to enhance the dispersion uniformity of graphene in HDPE matrix and interface bonding between graphene and HDPE matrix, this thesis prepared HDPE/graphene composite by three compounding methods including melt blending, modified melt blending and ethanol media blending-melt blending.And then we studied modified effect of compounding methods and graphene content on properties of HDPE.In this thesis, the conductive properties of composites prepared by three compounding methods were tested. The electrical conductivity of the composites was improved dramatically with the increase of graphene content,which showed the percolation phenomenon. Modified melt blending and ethanol media blending-melt blending obtained the same modified effect on the conductive properties of composites, and the percolation threshold of twokinds of composites are about 4.82 wt%(2.16 vol%); a better improvement of conductive property by melt blending was obtained, and the percolation threshold is about 3.75 wt%(1.67 vol%). In addition, two kinds of graphene wrapped HDPE powder were prepared by modified melt blending and ethanol media blending-melt blending. The conductive properties of composites prepared by two kinds of graphene wrapped HDPE powder were tested.Composites have better electrical conductivity. The percolation threshold of composite prepared by modified melt blending is 1.32 wt%(0.58 vol%),and the percolation threshold of composite prepared by ethanol media blending-melt blending is 0.78 wt%(0.34 vol%).And then the mechanical performance of composites prepared by three compounding methods was tested by universal mechanical testing machine.The tensile and flexural properties of composites are improved. The modification effect of ethanol media blending-melt blending is the best. It is attributed to better dispersion of graphene and strong interfacial interaction between graphene and HDPE matrix.The tensile strength and Young’s modulus of composites are increased by 4.9% and 28.2% respectively. The flexural strength and flexural modulus of the composites increased by 16.4%and 27.8% respectively.But the toughness of composites decreases with the increase of graphene content.The toughness of composite prepared by ethanol media blending-melt blending has a minimum reduction among three methods.