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Keywords:

  • polyacrylonitrile;
  • carbon fiber;
  • thermal stabilization;
  • dehydrogenation;
  • kinetics

Abstract

The kinetics of dehydrogenation reaction and the structural evolution in polyacrylonitrile precursor fibers during thermal stabilization in air have been studied by Fourier transform infrared spectroscopy. The results indicate that, with the progress of dehydrogenation, the absorbance of methylene groups ([BOND]CH2[BOND]) gradually decreases, whereas that of methine groups ([DOUBLE BOND]CH[BOND]) gradually increases. The dehydrogenation reaction in the fibers is basically completed after 20-min stabilization above 255°C. According to the Beer–Lambert law, the values of the absorbance for both [BOND]CH2[BOND] groups and the resulting [DOUBLE BOND]CH[BOND] groups have been calculated and converted into the concentration fractions of [BOND]CH2[BOND] groups via the Lorentzian multipeak fitting. According to the principles of chemical kinetics, the dehydrogenation reaction has been determined as a pseudo-second-order reaction with an activation energy of 107.6 kJ mol−1. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013