| The thesis dealt with the methods and processes of preparation of high thermalconductive polymer composites. The high thermal conductive composites based on PPor PTFE were manufactured. And the thermal conduction model and equation of filledpolymer composites were brought up by percolation theory. It was found that filling polymer with inorganic or metal powder of high thermalconduction could obviously improve the thermal conduction of polymer. Filling PPwith graphite could improve the thermal conductivity of modified composites. Theresults showed that with the increase of the content of graphite, the thermalconductivity of graphite/PP modified composites improved slowly; when the contentreached certain critical value, the thermal conductivity increased rapidly. When themass fraction of graphite was 55%(volume fraction was 44%), the thermalconductivity of graphite/PP composites came up to 1.29 W/(m·K),being more than 6times than pure PP. Filling aluminum powder in PP could also improve the thermal conduction of PP.When the mass fraction of aluminum powder was 55%(volume fraction was 28.9%),the thermal conductivity of aluminum powder/PP modified composites came up to1.02 W/(m·K),being more than 5 times of that of pure PP. In this paper, graphite/PTFE modified composites was prepared by mouldpressing. It was founded from the SEM investigation of modified composites that,graphite were uniformly distributed in PTFE matrix, and with the increase of contentof graphite, the probability of connecting flake shaped graphite each other becamemore. When the mass content of graphite varied from 0% to 10%, graphite becamedispersed phase, and PTFE was continuum. It presented island structure as a whole.When the content of graphite surpassed 10%, some pieces of graphite began toconnect each to form local thermal conductive chains. As the content came up to 40%,more graphite connected each other, and formed thermal conductive network. Measurements of thermal conductivity of graphite/PTFE modified compositeswere performed by utilizing thermal conductive tester. We found that thermalconductivity of composites were linearly related to mass contents of graphite whenmass contents of graphite was less than 10%. And the thermal conductivity ofcomposites began to increase rapidly around the point where graphite accounts for III10% in mass. This could be explained by the distribution of graphite in PTFE matrix. The thermal conductivity of graphite/PTFE modified composites increase to 1.2W/(m·K),more than 5 times than pure PTFE, when the content of graphite accountsfor 30% in mass. Because the tensile strength of modified composites is 13.2MPa, it isdifficult to be applied in effect. We compound the long carbon fiber with surfacetreatment with graphite/PTFE modified composites, and the results showed thatproper distribution of graphite and a few CF in PTFE matrix could obviously improvethe thermal conductivity and mechanical properties. When the mass ratio of PTFE andgraphite is 70/30, adding 3% CF to composites, the thermal conductivity ofcomposites was 1.2 W/(m·K), and tensile strength came up to 53.9MPa, more than 4times than graphite/PTFE modified composites. So it could be applied in effect. Whenthe content of CF was 6.2%, the strength came up to 86.6MPa; the content of CF was9.2%, the tensile strength was 119.6MPa, surpassed the mechanical property werequired. Comparing some typical equation with experimental data of filled thermalconductive composites, thermal conducting equation of describing phase distributionof parallel block composites did not applied in graphite/PTFE composites; Maxwell'sequation was only adaptable for low content; and Agari.Y's equation was notadaptable for superhigh content. On the basis of distribution of filler in polymer matrix accords with percolationtheory and it is applied in electrical conductive composites. The island-network modelis pro...
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