关键词: 静电纺丝, 间位芳纶, 纳米纤维, 过滤性能, 耐热性能

Abstract: Meta aramid (PMIA) is a kind of high-performance fiber, which has many excellent properties such as high strength, high modulus, high temperature resistance, chemical corrosion resistance, dimensional stability and so on. It is widely used in the fields of high temperature protection, industrial filtration and new energy. With the research and development of nanofiber technology, PMIA nanofibers have received extensive attention in the filtration field due to their high specific surface area, micro effects, interface effects and many other characteristics. Electrospinning is one of the common methods to prepare nanofibers and it has the advantages of low cost, simple operation and continuous preparation of controllable nanofibers. At present, researchers have studied the basic conditions of PMIA dissolution and electrospinning process respectively, and prepared nanofiber filter membranes with high filtration efficiency by using special technologies such as electrostatic spray screen. However, there are problems such as relatively large average diameter of nanofibers, decreased filtration efficiency of nanofiber membranes, large pressure drop, high equipment requirements and complex process.
Firstly, we explored the influence of electrospinning process parameters, such as the concentration of solute in spinning solution, electrospinning voltage, feed flow rate and collection distance on the diameter and morphology of nanofibers, obtaining the optimal process parameters. Secondly, we explored the influence of the spinning time on the filtration performance of composite filter materials by controlling the spinning time so that nanofiber filter membranes with different thicknesses could be formed on the substrate. Thirdly, we compared the changing rule of the filtration performance of the electrostatic filter materials whose static electricity is eliminated by isopropanol vapor with that of the filter materials without eliminating static electricity. Finally, the thermal dimensional stability and thermogravimetric stability of electrospun filter materials were studied and analyzed. By controlling and optimizing the morphology of PMIA nanofibers, filter materials with high efficiency and low resistance could be obtained. The results show that when the spinning solution concentration is 8%, the spinning voltage is 20 kV, the feeding speed is 0.3 mL/h, and the receiving distance is 15 cm, the average diameter of the obtained nanofibers is small, the fibers are smooth and regular, and the morphology is good. When the spinning time is 5 h, the filtration efficiency of the nanospun membrane for NaCl aerogel particles with median particle size of 0.26 μm reaches 99.5%, and the resistance is only 123.8 Pa. After electrostatic treatment, the filtration efficiency can still reach 89.4%; the size of the nanofiber membrane is basically unchanged in the temperature range of below 290 ℃, and the thermal weight loss at 400 ℃ is only 5%.
The electrospun PMIA nanofiber filter material has good filtration performance, dimensional stability and high temperature resistance, and is easy to be prepared on a large scale. It has an important application prospect in the field of high temperature and high efficiency filtration.

Key words: electrospinning, meta aramid, nanofiber, filtration property, heat resistance