An investigation on structure characterization of thermally stabilized polyacrylonitrile precursor fibers pretreated with guanidine carbonate prior to carbonization

Abstract

Thermal stabilization of polyacrylonitrile (PAN) precursor fiber was performed with a pretreatment of an aqueous guanidine carbonate solution and its structure was thoroughly characterized using a combination of infrared spectroscopy (IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), density, elemental analysis, and X-ray diffraction measurements. The use of guanidine carbonate pretreatment of polyacrylonitrile precursor fiber was found to be very useful for the acceleration of thermal stabilization of polyacrylonitrile precursor fiber prior to the carbonization stage. The results obtained from density, thermal analysis (TGA and DSC), infrared-spectroscopy and X-ray diffraction methods suggested an accelerated thermally stable aromatic ladder structure formation resulting in much reduced thermal stabilization time. X-ray observations showed the transformation of the original structure from a highly ordered phase to a totally disordered amorphous phase which seemed to be a direct consequence of the crosslinked and cyclized structure present in the stabilized fibers. The results obtained from the infrared spectra of thermally stabilized samples showed a rapid and simultaneous cyclization and dehydrogenation reactions aided by the oxygen uptake in the form of oxygen containing functional groups. Guanidine carbonate pretreated and thermally stabilized PAN precursor fibers showed a carbon yield of 52.5% at 11008C obtained from TGA measurements. The use of guanidine carbonate pretreatment is expected to significantly increase the productivity of carbon fiber manufacturing at a substantially reduced cost by significantly reducing the time necessary for thermal stabilization of polyacryonitrile fiber. POLYM. ENG. SCI., 52:937-952, 2012. 943 FIG. 13. Elemental composition of unstabilized and thermally stabilized polyacrylonitrile fibers pretreated with 15% guanidine carbonate solution and stabilized at 2408C as a function of stabilization time. (&) carbon (%); (*) nitrogen (%); (l) oxygen (%); (!) hydrogen (%).

Microwave pre‐oxidation for polyacrylonitrile precursor coated with nano‐carbon black

“…The intensity of the out‐of‐plane bending of CH at 802 cm −1 slightly increased and shifted to 806 cm −1 . The carbonyl (CO) stretching band located at 1728 cm −1 was weakened and shifted to a lower wavenumber, and it was only observed as a shoulder on the main conjugation absorption with the increase of pre‐oxidation time, suggesting that the carbonyl group became a part of the conjugated structure . Moreover, the absorption near 1260 cm −1 for various COC stretches can be attributed to crosslinking bonds .…”

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Studies of reaction mechanisms during stabilization of electrospun polyacrylonitrile carbon nanofibers

“…Different chemical reactions such as cyclization, oxidation, dehydrogenation, and cross‐linking may occur during stabilization of ePAN nanofibers , which are schematically shown in Fig. .…”

Development of a disposable electrode modified with carbonized, graphene‐loaded nanofiber for the detection of dopamine in human serum

“…Following stabilization and carbonization at high temperatures (280–800°C), the nanofibers were heated and formed a ladder structure through exothermic reactions, which may include dehydrogenation, cyclization, and crosslinking . Therefore, the nanofiber diameters for each composition were slightly decreased with partial uniformity, and the fibers were shortened and exhibited low aspect ratios after grinding .…”