Introduction of a Methodology to Enhance the Stabilization Process of PAN Fibers by Modeling and Advanced Characterization

Abstract

A methodology for designing the oxidative stabilization process of polyacrylonitrile (PAN) fibers is examined. In its core, this methodology is based on a model that describes the characteristic fiber length variation during thermal processing, through the de-convolution of three main contributors (i.e., entropic and chemical shrinkage and creep elongation). The model demonstrated an additional advantage of offering further insight into the physical and chemical phenomena taking place during the treatment. Validation of PAN-model prediction performance for different processing parameters was achieved as demonstrated by Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). Τensile testing revealed the effect of processing parameters on fiber quality, while model prediction demonstrated that ladder polymer formation is accelerated at temperatures over 200 °C. Additionally, according the DSC and FTIR measurements predictions from the application of the model during stabilization seem to be more precise at high-temperature stabilization stages. It was shown that mechanical properties could be enhanced preferably by including a treatment step below 200 °C, before the initiation of cyclization reactions. Further confirmation was provided via Raman spectroscopy, which demonstrated that graphitic like planes are formed upon stabilization above 200 °C, and thus multistage stabilization is required to optimize synthesis of carbon fibers. Optical Microscopy proved that isothermal stabilization treatment did not severely alter the cross section geometry of PAN fiber monofilaments.

Effect of the cation structure on the properties of homobaric imidazolium ionic liquids

“…53 According to the literature, cyclisation is the main reaction occurring for polyacrylonitriles in the temperature range of 180 to 240 1C. 54 The final products from this reaction are various imine structures through oligomerisation of the nitrile groups. In order to investigate if this is indeed the case in our system we heated the ILs to 200 1C for a few hours which resulted in a dark-coloured sticky product without any significant mass loss, which is an indication that such polymerisation reactions are taking place.…”

Exothermic Behavior and Structural Transformation of Large-Tow Polyacrylonitrile Fibers during Thermo-Oxidative Stabilization

“…The increased number of filaments will aggravate the difference in the FN groups of small and large fiber bundles and the FN groups of the center fiber and surface fiber. In addition, the reaction enthalpy of stabilized fibers can reflect the degree of fiber reaction. ,, As Figure c shows the DSC curves of the center fiber and surface fiber of different filament bundles when heated for 2 min. The reaction enthalpy of fibers was obtained by integrating the exothermic peak, as shown in Figure d.…”

“…In addition, the reaction enthalpy of stabilized fibers can reflect the degree of fiber reaction. 35,38,39 As Figure 7c shows the DSC curves of the center fiber and surface fiber of different filament bundles when heated for 2 min. The reaction enthalpy of fibers was obtained by integrating the exothermic peak, as shown in Figure 7d.…”

Research on Improving the Pre‐Oxidation Process of the Excellent Mechanical Strength Carbon Fiber

“…[9][10][11] DOI: 10.1002/macp. 202300114 Various pretreatment methods are used on PAN fibers to manufacture low-cost carbon fibers and improve their mechanical properties, such as annealing before the pre-oxidation process, [12,13] hydroxylamine hydrochloride treatment, [1] heating in a nitrogen atmosphere, [14] or microwave treatment. [15] These modifications benefit the cyclization reaction during the pre-oxidation process, saving time and energy and enhancing the carbon yield.…”