Study On Mechanical Properties And Thermal Conductivity Of HDPE/Elastomer/Graphite Composites

Mechanical properties and thermal conductivity of HDPE/elastomer/graphite composites were studied in this thesis. The factors that affected mechanical properties and thermal conductivity of HDPE composites were also discussed.The influence of the surface modification of graphite, the species (NDZ101, TM101, and TM200S) and content of the coupling agents on mechnical properties of HDPE/elastomer/graphite composites was studied; the species (colloid graphite, squama graphite, and expanded graphite), particle size, and content of graphite on mechnical properties and processing properties of HDPE/elastomer/graphite composites were also studied. The results indicated that HDPE composites filled with colloid graphite had the highest notched impact strength, while HDPE composites filled with expanded graphite had the lowest notched impact strength; the flexural strength of HDPE composites filled with expanded graphite was the best, whle that filled with colloid graphite was the worst; the tensile strength of HDPE composites filled with various speices of graphite was almost the same. With increasing the colloid graphite content, the tensile and flexural strength of HDPE composites increased, whileas the notached impact strength of HDPE composites descreased. The particle size of colloid graphite had hardly effect on tensile and flexural strength of HDPE composites. With an increase of the particle size of colloid graphite, the processing properties of HDPE composites became worse. When the content of POE is 5%, the mechanical property of HDPE/POE/graphite composites was good. POE and EVA can significantly improve ESCR of HDPE composites.The effect of the particle size of colloid graphite on crystallization of HDPE was studied. When the particle size of colloid graphite was more than 4 m, the crystallization degree and speed of HDPE decreased with the increase of the particle size; when the particle size of colloid graphite was less than 4 m, the crystallization degree and speed of HDPE increased with the increase of the particle size.The effect of the species, content and particle diameter of the graphite on the thermal conductivity of HDPE was studied. The results showed that with the increase of the graphite content, the thermal conductivity of HDPE/POE/graphite composites increased. The thermalconductivity of HDPE composites filled with the expanded graphite was better than that of the colloid graphite, and at the same content (7 vol %) the thermal conductivity of the former was one times larger than that of the latter. The particle diameter of the graphite also affected the thermal conductivity of HDPE composites. The experimental results showed that with the increase of the particle size of the colloid graphite, the thermal conductivity of HDPE/POE/graphite composites increased. Some models, such as Maxwell-EucKen. Cheng and Vochon, Zieblend, Lewis and Nielsen , Agri and Uno equations proposed to predict thermal conductivity of polymer composites in a two-phase system could not be applied to HDPE composites filled with graphite, while Zieblend equation was suitable for HDPE composites except some constants.Hydraulic strength, demolition strength, and weldability of the thermal conductive pipe prepared by HDPE/POE/graphite composites were studied. It was found that the performance of the pipe prepared by HDPE/POE/graphite composites was completely satisfied for themal conductive plastic pipe of ice cumulation energy.