New aspects in the oxidative stabilization of PAN-based carbon fibers

Gupta, Abhishek; Harrison, I. R.

doi:10.1016/s0008-6223(96)00094-2

Cited by 246 publications

(147 citation statements)

References 12 publications

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“…Furthermore, stabilized fibers for more than 10 min did not dissolved in DMSO for 7 days. Gupta and Harrison studied stabilization of co-polymer PAN as temperature increased up to 380˚C with a heating rate of 1˚C/min, and claimed intramolecular cyclization and intermolecular cross-linking reactions took place in amorphous and crystalline regions at a different temperature range [14]. According to their report, intramolecular cyclization reactions started in amorphous and crystalline region at 175˚C and ~215˚C.…”

mentioning

confidence: 99%

Structural Evolution of Polyacrylonitrile Fibers in Stabilization and Carbonization

Lee¹,

Kim²,

Ku³

et al. 2012

ACES

201

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The effect of structural evolution polyacrylonitrile (PAN) on mechanical properties was investigated in stabilization and carbonization. PAN spun fibers were stabilized in a convection oven with a constant tension for various times at 250˚C. Fourier Transform Infrared spectroscopy (FTIR) and gel fraction results suggested that intra and intermolecular stabilization reactions occurred simultaneously. X-ray diffractograms revealed a disruption of crystalline structure and an appearance of pre-graphitic structure of PAN fibers due to stabilization. These structural changes by stabilization resulted in the significant decrease of tensile properties of fibers. In Raman spectra with heat treated fibers from 400˚C up to 1200˚C, the intensity ratio of the D to G bands (I D /I G ) decreased as heat treatment temperature increased, indicating an increase of basal plane of graphitic layer of heat treated fibers. Tensile strength of heat treated fibers at 1200˚C was found to be as high as 2.2 GPa.

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mentioning

confidence: 99%

Structural Evolution of Polyacrylonitrile Fibers in Stabilization and Carbonization

Lee¹,

Kim²,

Ku³

et al. 2012

ACES

201

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“…42 As the temperature is raised, due to loosening of intermolecular dipole-dipole interactions, adjacent nitrile groups of the same macromolecule repel each other and these interactions increase activation volume. 20,35,43,44 Rubbery flow is occurred with contribution of imposed stresses and fibers start to elongate. Before this region, fibers show shrinkage behavior due to lower applied stress (Fig.…”

Section: Second Return and Sans Return Behaviormentioning

confidence: 99%

A Novel Method for Investigation of Entropic Stress in Prestabilization of PAN‐Based Precursor Fibers

2015

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ABSTRACT:Applying stress in the fiber axis direction during the prestabilization process is the best method to control entropic relaxation. Evaluation of entropic stress is necessary for exact determination of required imposed stress. Accordingly, in this paper three types of special-grade polyacrylonitrile (PAN) fibers with different physical-mechanical properties and morphological characteristic are studied. To determine thermal-induced entropic stresses, we use the thermomechanical analysis method from room temperature to beginning of chemical reactions under certain stresses. It is shown that three thermophysical behaviors including the first return, second return, and sans return occurs under certain stresses during the thermal process. There are distinct temperatures for the first and second return behaviors, in which fibers return to primary length after shrinkage or elongation. These temperatures depend on imposed stress during prestabilization. We found that if no elongation or fiber shrinkage occurs in a specific stress and temperature, it shows that imposed stress is equivalent to thermal entropic stress. Changes in shrinkage as a function of temperature for various external imposed stresses are also observed. According to our findings, the onset of entropic stress strongly depends on the orientation index of the paracrystalline region. The maximum entropic stress occurs in the rubbery flow region in amorphous phases and can be obtained from a derivative of the second-order polynomial trend line of the entropic stress-temperature diagram.

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“…2). 23 Endothermic reaction is a melting point that copolymer is molten. In addition, exothermic reaction is temperature of dehydrogenation and cyclization reactions of the PAN.…”

Section: −11mentioning

confidence: 99%