Utilizing B-Stage Amine-Epoxy in Electrospinning of Amine-Epoxy/Poly(vinyl alcohol) Nanofiber Webs for Direct CO<sub>2</sub> Capture from the Air

To achieve carbon neutrality by 2050, there is an increasing need to actively capture carbon dioxide (CO2) from the atmosphere. Direct Air Capture (DAC) has attracted attention as a method for directly capturing CO2, and amine-based compounds have been actively studied as CO2 adsorbents. By polymerizing amine and epoxy, we developed thermosetting DAC nanofibers with excellent low-temperature desorption properties and excellent heat resistance. In the fabrication of epoxy-crosslinked amine nanofibers by the electrospinning process, polyvinyl alcohol (PVA) was added to improve spinnability, and direct spin-line heating in the electrospinning process was successfully performed for in-situ thermal polymerization. However, because of the relatively high energy consumption of the process, we tried to produce amine-epoxy/PVA nanofibers through a process that does not require spin-line heating in this research. For this purpose, amine and epoxy were reacted in advance to convert them to B-stage. With the highly B-staged spinning solution, AE/PVA nanofibers of approximately 500–700 nm diameter could be produced without spin-line heating. When the B-stage state was low, in-situ heating during the electrospinning process was required, as in the previous report, however, the temperature required for the formation of fibers decreased with the increasing degree of B-stage. When the spin-line heating temperature was low or without the spin-line heating, additional annealing of the prepared web was required to complete the polymerization, even though fabrication of nanofibers was possible in the electrospinning. We confirmed that the obtained amine-epoxy/PVA nanofiber web had the same CO2 adsorption performance as in-situ polymerized nanofibers. In addition, by B-staging, the viscosity of the spinning solution increased, making it possible to reduce the concentration of the PVA aqueous solution, and it became possible to obtain nanofibers with a higher amine-epoxy ratio.