Effect of KMnO4 on chemical, crystal and microscopic structure of polyacrylonitrile fibers

Abstract

Abstract The effects of modification temperature and time on polyacrylonitrile (PAN) fibers under various concentrations of KMnO4 were studied. Wettability, colouration, chemical structure (Fourier transform infrared spectroscopy), crystal structure (X-ray diffraction), stack domains (D), interlayer spacing (d), microscopic structure (Scanning electron microscopy) and elemental content (energy dispersive spectroscopy) were analysed. Aside from its good hydrophilicity, KMnO4 at 2 and 4 wt% are beneficial to the modification of PAN fibers. The colouration of the fiber at 80 °C is the most obvious. The clear peak of the pre-oxidised fibers at 2340 cm−1 corresponds to the conjugated structure of MnO4–C N. At 4 wt%, the degree of pre-oxidation is too high and the main infrared peak disappears. M2, 30 has a minimum D of 9.320 nm and 8.258 nm at 2θ = 16.883° and 2θ = 29.673°, respectively, and the fiber crystals are the finest. At a content of 4 wt%, the fibers are axially cracked and crystals appear on the surface. M2, 30 and M2, 60 have a close percentage of C element, whereas M2, 30 has a lower percentage of Mn element. The best modification conditions of KMnO4 are 2 wt%, 80 °C and 30 min.