Kinetic study of the dehydrogenation reaction in polyacrylonitrile‐based carbon fiber precursors during thermal stabilization

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 (ACH 2 A) gradually decreases, whereas that of methine groups (¼ ¼CHA) 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 ACH 2 A groups and the resulting ¼ ¼CHA groups have been calculated and converted into the concentration fractions of ACH 2 A 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 À1 .

Manufacturing and characteristics of PAN-based composite carbon fibers containing cellulose particles

“…in the stabilization process of the PAN fibers. Our results are in agreement with the assertions by Xue et al [21].…”

“…1. The stabilization process for PAN fibers was first described by Xue et al [21] as the extinction of the PAN structure resulting from cyclization and dehydrogenation from the oxidation reaction to establish thermal stability. The extinction of the crystallinity for the (010) and (300) planes of PAN was observed as a result of the destruction of the structure by decomposition or oxidation of O 2 or OH, etc.…”

A simple PAN-based fabrication method for microstructured carbon electrodes for organic field-effect transistors

“…Thus, it has been commonly used not only in the fabrication of clothing and soft furnishing fibers but also as an important precursor for the fabrication of carbon fibers having high mechanical strength and high conductivity [19][20][21]. In this respect, PAN can be a promising polymer precursor for the formation of electrically-conductive GCMs.…”

Preparation and thermal stability of initiator fragments end-capped oligomers/silica nanocomposites

“…On the other hand, it is well known that polyacrylonitriles (PANs) are widely used as precursors for fabricating high performance carbon fibers [8][9][10][11][12][13][14][15]. The formation of PAN precursor fibers possessing the heatresistance ability by heating to 200 ∼ 300°C is due to the change of the chemical structure from the linear molecular chain into ladder structures through a variety of chemical reactions including cyclization of nitrile groups leading to hydronaphthiridine rings, dehydrogenation leading to a certain degree of aromatization, and oxidation reaction leading mainly to acridone and some other structure [9,11,12].…”

“…The formation of PAN precursor fibers possessing the heatresistance ability by heating to 200 ∼ 300°C is due to the change of the chemical structure from the linear molecular chain into ladder structures through a variety of chemical reactions including cyclization of nitrile groups leading to hydronaphthiridine rings, dehydrogenation leading to a certain degree of aromatization, and oxidation reaction leading mainly to acridone and some other structure [9,11,12]. From this point of view, it is of particular interest to study on the thermal stability of initiator fragments end-capped oligomers, which should be synthesized by using a variety of radical initiators containing not only the nitrile groups but also the 2-methyl-N- (2-hydroxyethyl)propionamide and the sulfate ester units.…”