Study of the properties for stabilized polyacrylonitrile thermally treated in air

Developing of nanotechnology-based electronics entails developing of new carbon nanocrystalline materials with predetermined physicochemical properties, e.g., obtained by synthesis of polyacrylonitrile (PAN) in conditions of heat treatment. We have studied the properties of PAN heat-treated in air in the temperature range 150 – 250°C and the effect of stabilization on the kinetic parameters of synthesis and thermochemical properties of carbon material upon heat treatment in N₂ atmosphere. It is shown that an increase in the temperature of a preliminary treatment up to 200°C leads to a decrease in the activation energy and pre-exponential factor compared to the corresponding values characteristic for the initial polymer (from 90.9 and 3.1 × 10⁶ to 53.3 kJ/mol and 1.1 × 10³ min^–1, respectively), which indicates to the occurrence of diffusion limitations. When the temperature of a preliminary treatment in air increases from 180 to 250°C, the difference between temperature peaks for DSC and TGA curves decreases due to appearance of a «core-shell» structure. XRD data indicate that the initial PAN structure does not change up to 150°C. Further increase in the temperature leads to significant changes in the initial structure of the polymer which are manifested in a decrease in the peak area in the X-ray diffraction pattern of the polymer. The results obtained can be used in the development of a method for the synthesis of carbon materials with controlled properties predetermined at the stage of stabilization.

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