Polyimide film carbonization and graphitization
Oct 18,2024
Enray
With the study of the carbonization process of polyimide film, it is found that the most dramatic change in the polymer chain structure of polyimide is inBefore 650 ℃, the first occurrence of imide ring alongC-NBond cleavage and decarbonylation occur to form benzene ring compounds with conjugated nitrile and isonitrile groups,650 ℃After the combination of heterocyclic ring and removal of residual nitrogen and oxygen, the generation of continuous huge aromatic heterocyclic compounds, and then by the fused ring aromatization, the hexagonal carbon network layer of graphite-like structure is formed and gradually increased. When the heating temperature reaches700 ℃When observed to represent a similar carbon hexagonal network surface.(002)The diffraction peaks appear, and the diffraction intensity increases with the increase of pyrolysis carbonization temperature.
Polyimide films in the prior art are mostly used in flexible circuit boards, although some are obtained by sintering polyimide films.graphite heat sink, so as to be attached to the heat source.In a carbonization furnace with a temperature controller, the multilayer film is first laminated under a certain pressure and temperature control in a nitrogen atmosphere, and then incarbonization furnacemedium carbonization, the carbonization temperature is800 ° C. The carbonized polyimide film is placed in a medium frequency induction graphitization furnace.2500-2800 ℃Heat treatment is performed.
Graphitization process: vacuumAbout 10Pa power transmission temperature rise, heating rate10℃/min, rose2000 ℃Stop vacuuming, heat preservation0.5hPost-filling with argon0.09Mpa, and then continue to heat up, in2500-2800 ℃Insulation2hand then the sample was cooled with the furnace.
PIAfter further high temperature heat treatment, the film shrinks obviously in the thickness direction and increases slowly in the diameter direction. The size of the carbon film graphite planar aromatic ring also grows slowly, and gradually forms a three-dimensional ordered graphite structure between the layers, but there are obvious size shrinkage, cracks and holes, and the texture becomes brittle..
With the increase of heat treatment temperature, the density of different polyimide films decreased, the opening rate increased, the bending strength decreased, the volume resistivity decreased, and the thermal conductivity increased. after pyrolysisBTDA/BAPF polyimide films exhibit good properties,2800 ℃After treatment, density1.6g/cm3Opening rate1.0%, bending strength90MPa, volume resistivity38-45Ω · cm, thermal conductivity17 kcal/M · h · ℃
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