Abstract: The damage of air pollution to human health is receiving more and more attention with the development of society. Protective materials for isolating harmful particles, bacteria, viruses and other harmful microorganisms have attracted unprecedented attention due to the unexpected COVID-19 in the past three years. Preparing more efficient and low-resistance air filter materials has important practical significance.
Nanofiber membranes prepared by electrospinning technology have the advantages of smaller fiber diameter and higher porosity compared with traditional filter materials. They have been a hot research in the field of high efficiency air filtration in recent years. To expand the application of electrospun nanofiber membranes in the air filtration field and to develop more efficient and low-resistance air filtration materials, polyurethane was used as the raw material, tetrahydrofuran (THF) and N, N-dimethylformamide (DMF) were used as solvents in this paper. The polyurethane nanofibers prepared by electrospinning had dendritic branches by adding different kinds of salts to the spinning solution, and the conductivity of the spinning solution was increased. The dendritic structures made the pore size of the nanofiber membranes smaller to further improve the filtration efficiency. The influences of the spinning voltage, salt type and addition on the morphology, hydrophobicity and air filtration of the fiber membrane were studied. The results show that at a solution concentration of 14%, the type of salt and spinning voltage have great influence on the branching structure, and the branching structure of polyurethane nanofiber membranes is most obvious when the TBAC is added with the spinning voltage being 35 KV. Meanwhile, The contact angle of fiber membranes decreases from 99.1° to 82.8° with the addition of the salts (the hydrophilicity of membrane materials increases), which can improve the moisture absorption and moisture conductivity of air filter materials in a certain level. The filtration performance is significantly improved (the filtration efficiency increases from 50.8% to 93.6%). The branching superfine nanofibers can further reduce the pore size of the ninafiber membrane, which can separate smaller size particles; the specific surface area increases as the fiber becomes thinner, and thus the contact area between particles and fibers increases; the probability of adsorbing and capturing particles increases, and thus increases the filtration efficiency of the fiber membrane. At the same time, due to the smaller diameter, the resistance of the branched ultrafine nanofibers is correspondingly reduced, so that the filtration resistance of the filter material is also maintained at a low level, and the quality factor that can reflect the comprehensive filtration performance of the filter material is improved from 0.009 to 0.073. Therefore, ultrafine nanofibers are suitable for high-efficiency and low-resistance air filtration materials. 

Key words: polyurethane, electrospinning, nanofiber membrane, air filtration, filter performance

摘要： 为拓展静电纺纳米纤维在空气过滤领域中的应用，以聚氨酯（PU）为原料，通过加入不同种类的盐，采用静电纺丝法制备树枝状PU纳米纤维膜。利用扫描电镜（SEM）、接触角测试仪、红外光谱仪、自动滤料测试仪测试纳米纤维膜的微观结构、亲疏水性、化学结构和过滤性能。结果表明：PU质量分数14%条件下，添加有机盐TBAC，纺丝电压35 kV时，制备的纳米纤维膜的树枝状分叉结构明显；TBAC的加入使纤维膜的接触角由99.1°减小到82.8°；分叉结构使纳米纤维膜的过滤性能显著提高，与纯PU纳米纤维膜相比，过滤效率从50.8%提高到93.6%，品质因子从0.009提高到0.073，可满足高效低阻空气过滤材料的需求。

关键词: 聚氨酯, 静电纺丝, 纳米纤维膜, 空气过滤, 过滤性能