Development of High Ductility and Tensile Properties upon Two-Stage Draw of Ultrahigh Molecular Weight Poly(acrylonitrile)

In situ study of the preoxidation of polyacrylonitrile fibers

In the production of polyacrylonitrile-based carbon fibers (PAN-CFs), preoxidation is a key step to improving the thermal stability of the fibers and forming their structural prototype. However, structural evaluation of PAN fibers during preoxidation remains ambiguous, partly due to a lack of in situ studies. This contribution reports an in situ study of the preoxidation of PAN fibers using wide-angle X-ray scattering and small-angle X-ray scattering techniques on a synchrotron radiation beamline. The structural changes of the skeleton and pores in the fibers are revealed and correspond to five kinds of diffraction spots (peaks) and two kinds of scattering streaks, respectively. The preoxidation shows obvious stages, and the corresponding possible mechanism is analyzed.

BaTiO3 assisted PAN fiber preparation of high performance flexible nanogenerator

Recently, polyacrylonitrile (PAN) fiber films have shown greater advantages over polyvinylidene fluoride (PVDF) in the field of energy harvesting. Adding other substances with high piezoelectric coefficient is worth exploring to further improve the output voltage of PAN. Here, we successfully dispersed high dielectric constant barium titanate in PAN nanofiber films with different dosages using an electrospinning technology. The X-ray diffraction and Fourier transform infrared spectroscopy results indicated that BaTiO₃ nanoparticles aid in transforming PAN from a 3¹-helical conformation to a planar zigzag conformation, thus improving the output voltage of PAN nanofibers significantly and also promoting its mechanical properties. In addition, the human body function monitoring experiment showed a good response current to the rhythm of elbow bending, knee bending, running, and breathing. Besides, when a simple rectifier circuit was applied, the capacitor could be charged to 2 V in less than 2 min and light a commercial LED through repeated tapping.

Synthesis of electrospun polyacrylonitrile- derived carbon fibers and comparison of properties with bulk form

This study deals with the fabrication of polyacrylonitrile (PAN) nanofibers via an electrospinning process followed by stabilizing and carbonization in order to remove all non-carboneous matter and ensure a pure carboneous material. The as-spun PAN fibers were stabilized in air at 270°C for one hour and then carbonized at 750, 850, and 950°C in an inert atmosphere (argon) for another one hour. Differential scanning calorimetry and Raman spectroscopy were employed to determine the thermal and chemical properties of PAN. Surface features and morphologies of PAN-derived carbon nanofibers were investigated by means of scanning electron microscopy (SEM). SEM micrograms showed that fiber diameters were reduced after carbonization due to evolution of toxic gases and dehydrogenation. The Raman spectra of carbonized fibers manifested D/G peaks. The Raman spectroscopy peaks of 1100 and 500 cm^-1 manifested the formation of γ phase and another peak at 900 cm^-1 manifested the formation of α-phase. The water contact angle measurement of carbonized PAN fibers indicated that the nanofibers were superhydrophobic (θ > 150^o) due to the formation of bumpy and pitted surface after carbonization. In DSC experiment, the stabilized fibers showed a broad exothermic peak at 308°C due to cyclization process. The mechanical andThermal analysis was used to ascertain mechanical properties of carbonized PAN fibers. PAN-derived carbon nanofibers possess excellent physica and mechanical properties and therefore, they may be suitable for many industrial applications such as energy, biomedical, and aerospace.

Synthesis, characterization, and thermo-mechanical properties of poly(acrylonitrile-co-2,3-dimethyl-1,3-butadiene-co-itaconic acid) as carbon fibre polymer precursors

Graphical abstract shows a novel carbon fibre polymer precursor with improved thermal characteristics.