The Preparation Of High High Thermal Conductive Polyimide Grapheme And Performance Study

Prepared by the polyimide (PI) as precursor polyimide cornerstone ink film material as both a conventional carbon materials density low, high temperature resistance, corrosion resistance and high strength and high mode characteristics, but also has excellent conductivity and become excellent materials of electronic devices, aircraft and other advanced industry on the heat dissipation problem solving. At present, the conductivity of the carbon film sintered by PI thin film is more than 6.5×10 S/m, the conductivity of the graphite film reaches 2×105S/m, and the thermal conductivity exceeds 1500W/m K. But the domestic polyimide film is uneven, and the quality of the sintered graphite film is poor, and the conductivity is low, so it is difficult to meet the needs of the industry.In this paper, the structure and properties of PI based graphite films were observed by changing the process conditions in the synthesis of PI thin films. First by changing all four methyl benzene dianhydride (PMDA) and diamino diphenyl ether (ODA) cast material than the synthesis of polyamic acid solution by GPC method of polyamic acid (PAA) molecular weight size and distribution of PI based carbon membrane morphology and conductive properties of impact. Secondly, by means of elemental analysis of effects to solvent processing time of PI film and PI based carbon membrane, graphite membrane structure and performance; then, through DMA studied effects of the carbonization temperature of PI films and on conductivity of the graphite film. Finally, by analyzing the performance characteristics of all kinds of materials, the influence of the tensile conditions on the film properties and the structure and properties of PI based graphite films prepared by PI thin films were studied.Results show:(1) the synthesis of high molecular weight and narrow distribution of polyamide acid is conducive to improve the heat resistance of polyimide film, but also conducive to the preparation of high conductive properties of graphite film. However, since any single excess will have a greater impact on the resulting materials, it is not conducive to the preparation of high quality films by changing the monomer feed ratio of the method to control the molecular weight of polyamide acid. When the feed ratio is 1.01:1 obtained product MW 2.12×106, dispersion of 2.11; at this time the material thermal decomposition temperature is 588℃; the obtained polyimide materials in the carbonization of the surface defects are obviously fewer, the obtained carbon membrane conductivity for 7.18 * 103S/m and graphite conductive film rate was the highest 2.98x 104S/m.(2) to solvation process does not change the chemical structure of polyimide film, but go with solvent treatment time prolonged, polyamic acid resin film residual solvent content decreased. During the imidization process solvent of polyimide molecular chains of plasticization decreased. In the same thermal imide treating temperature, material of the imidization degree reduced and the thermal stability of materials decreased. And appropriate removal of solvent treatment can reduce the impurity content in the film to reduce defects in graphite film, help in the preparation of smooth smooth PI based carbon membrane, to the solvation time is 6h, maximum conductivity of the obtained graphite film is 4.63×104S/m.(3) pre carbonization treatment can effectively improve the materials of the imidization degree, in favor of materials in high temperature carbonization (graphitization) process improve the ordered degree, to regular crystalline graphitic structure transition. But excessive pre carbonization temperature lead to material thermo oxidative degradation and crosslinking reaction, destruction of the polyimide structure, materials are graphitised after the obtained graphite film order reduced. After carbonization treatment at 400℃, the D002 peak of the graphite film is close to the size of the graphite single crystal. At this time, the PI based carbon film conductivity is 9.24×103S/m, the conductivity of the graphite film is 27.78×104S/m.(4) in the process of the Bi direction stretching can effectively improve the thermal stability of the film, and mechanical properties, and also conducive to improve the conductivity of the graphite film. The tensile strength of the film is increased by 18.69%, the elongation at break is increased by 36.58% and the elastic modulus is increased by 2.86%. Nissan films are graphitised conductivity can reach 41.67×104S/m and domestic film in same graphitization treatment process and conductivity difference 25.94%.