关键词: 防电磁辐射性能, 导电性能, 聚丙烯腈, 聚苯胺, 纳米纤维

Abstract: Polyaniline (PANI), as a suitable conductive polymer, has many inherent and unique properties, such as reversible redox properties, electrical conductivity, sensing properties and pH switching. However, due to its poor mechanical properties and thermal stability, it is difficult to be used in the field of electromagnetic shielding materials alone. Due to the limitation of melt extrusion technology, polyaniline fibers can only be formed from the spinning solution during the spinning process. However, the existing methods of preparing polyaniline nanofiber membranes from polyaniline inevitably weaken the mechanical properties of polyaniline.
Based on electrospinning technology, the polyacrylonitrile (PAN) nanofiber membrane was used as raw material and immersed in aniline (An) acid solution, the polyaniline (PANI) coatings were prepared on the surface of PAN nanofibers by in-situ polymerization with the addition of APS (with a respective concentration of 0.1 mol/l, 0.2 mol/l, 0.3 mol/L, 0.4 mol/l and 0.5 mol/L), and the PAN/PANI composite nanofiber membrane was prepared. The microstructures, chemical structures, resistivity and electromagnetic shielding properties of the composite nanofiber membranes were investigated by means of scanning electron microscope, Fourier infrared spectroscopy, four-probe specific resistance tester and radiation protection tester. In addition, the effect of APS concentration on the electromagnetic shielding effectiveness of the composite nanofiber membrane was studied based on the regression analysis method. The results show that the nanofibers with random distribution on the surface of the composite nanofiber membrane have network structure and show dense structure. The nano-fibers on the surface of the PAN/PANI composite fiber membrane will break and become even and compact to agglomerate with the increase of oxidant concentration, which indicates that the oxidant concentration is too low. In other words, the low quality and low yield of PANI produced by An and APS make it impossible for PANI to effectively deposit on PAN, resulting in disconnection on the surface of nanofibers. The excessively high concentration of oxidant results in  agglomeration on the surface of nanofibers. Fourier infra-red spectra show that with the advent of in situ polymerization, the nitrile groups of PAN and PANI interact with each other to generate electrostatic interaction, while PAN and PANI do not react. With the increase of APS concentration, the resistivity of PAN nanofiber membrane decreases first and then increases, which indicates that when the concentration of APS is 0.3 mol/L, the quality of polyaniline is the best, and it can form a good conductive network on PAN, and can effectively absorb and shield electromagnetic waves. SEM photographs of the surface of the composite nanofiber membrane show that the size of APS is the smallest and the structure is the densest when the concentration of the oxidant is 0.3 mol/L, PAN is uniformly and compactly coated on PAN fibers, which improves the structural compactness of the fiber. The potential application of the PAN/PANI composite nanofiber membrane in functional wearable clothing is demonstrated by testing its anti-electromagnetic shielding performance.
This study provides scientific data for the preparation of PAN/PANI composite fiber membranes by in-situ polymerization, and provides a new idea for the development of PAN/PANI composite fiber membranes with high conductivity and anti-electromagnetic radiation.

Key words: anti-electromagnetic radiation performance, electrical conductivity, polyacrylonitrile, polyaniline, nanofiber