Structural Transformation of Polyacrylonitrile (PAN) Fibers during Rapid Thermal Pretreatment in Nitrogen Atmosphere

Abstract

The modification before the stabilization process could tune the exothermic behavior and the structural evolution of PAN fibers during stabilization. In this study, we demonstrate that a rapid thermal pretreatment in nitrogen can effectively mitigate the exothermic behavior of PAN fibers, such as decreasing the initial temperature, broadening the exothermal peak, and decreasing the nominal heat release during heating the fibers in air. The color of fibers has shown gradual changes from white to light yellow, yellow and brown during thermal pretreatment in nitrogen with the increase of pretreating temperature and time. The differential scanning calorimetry (DSC), Fourier Transform Infrared Spectrometer (FTIR), X-ray diffraction (XRD), and Thermogravimetric Analysis (TG) characterization have been applied to analyze the thermal properties, chemical and physical structural difference between PAN, and thermally pretreated PAN fibers. The thermal pretreatment of PAN fibers in nitrogen could induce cyclization, dehydrogenation, and cross-linking reactions, in which the cyclization play an important role on improving the cyclization index of stabilized PAN fibers. Meanwhile, the pretreatment can result in noticeable changes of the aggregation structure of PAN fibers, as indicated by the increase of crystallinity and crystalline size. These structural modifications can benefit the main cyclization reaction during stabilization and enhance the carbon yield in resultant carbon fibers. The rapid thermal pretreatment in nitrogen could increase efficiency of modification on PAN fibers, and that could save much time and energy. It is beneficial to manufacture low-cost carbon fibers and to spread the applications of carbon fibers.

Enhanced Thermal Stability and Electrochemical Performance of Polyacrylonitrile/Cellulose Acetate‐Electrospun Fiber Membrane by Boehmite Nanoparticles: Application to High‐Performance Lithium‐Ion Batteries

“…The diffraction peak at 2 θ = 17° corresponds to PCA, as reported in the literature, and is characteristic of the hexagonal structure of PAN. [ 36,37 ] The diffraction peak at 21.7° corresponds to the typical I β lattice characteristic peak of cellulose acetate, indicating that cellulose acetate is mainly amorphous. [ 38–40 ] With increasing boehmite content, the peak at 17° broadens and the peak height decreases, indicating a reduction in the crystalline integrity of the composites.…”

Nonflammable pre-carbonized polyacrylonitrile nanofiber webs

“…When an infrared (IR) beam is totally reflected on the inner surface of an ATR crystal, an evanescent wave is generated and penetrates the sample in contact with the crystal. The sample molecules absorb the IR radiation with wavelengths corresponding to their characteristic [15][16][17]. 1590 cm −1 was mainly assigned to C = N double bond [15,16,[18][19][20][21][22] also, together with the combination of C = N, C = C, N-H [16,18,21,22] and are presented in Fig.…”

Preparation and Characterization of Highly Porous Polyacrylonitrile Electrospun Nanofibers Using Lignin as Soft Template via Selective Chemical Dissolution Technique

“…It is noticeable that the PAN/lignin (8:2) in Figure S1 and the PAN/lignin (6:4) in Figure S2 show that weight loss exceeded 100%. The possible explanation for this is that the PAN fiber can have a reaction with nitrogen under thermal treatment [41] with a resulting weight increase of over 100%. From DTG thermograms, a sharp peak corresponding to a maximum decomposition temperature of PAN nanofibers is observed at 296 • C (Figure 5) and 299 • C (Figure 6) for before and after selective chemical dissolution, respectively.…”