key: cord-0835448-l3qdb7kj
authors: Wu, Junwei; Zhou, Hongjia; Zhou, Jingyi; Zhu, Xiao; Zhang, Bowen; Feng, Shasha; Zhong, Zhaoxiang; Kong, Lingxue; Xing, Weihong
title: Meltblown fabric vs nanofiber membrane, which is better for fabricating personal protective equipments
date: 2020-11-23
journal: Chin J Chem Eng
DOI: 10.1016/j.cjche.2020.10.022
sha: f0f38cd73773f7940fefbec79befb100f4bf4048
doc_id: 835448
cord_uid: l3qdb7kj

The coronavirus disease 2019 (COVID-19) pandemic has led to a great demand on the personal protection products such as reusable masks. As a key raw material for masks, meltblown fabrics play an important role in rejection of aerosols. However, the electrostatic dominated aerosol rejection mechanism of meltblown fabrics prevents the mask from maintaining the desired protective effect after the static charge degradation. Herein, novel reusable masks with high aerosols rejection efficiency were fabricated by the introduction of spider-web bionic nanofiber membrane (nano cobweb-biomimetic membrane). The reuse stability of meltblown and nanofiber membrane mask was separately evaluated by infiltrating water, 75% alcohol solution, and exposing under ultraviolet (UV) light. After the water immersion test, the filtration efficiency of meltblown mask was decreased to about 79%, while the nanofiber membrane was maintained at 99%. The same phenomenon could be observed after the 75% alcohol treatment, a high filtration efficiency of 99% was maintained in nanofiber membrane, but obvious negative effect was observed in meltblown mask, which decreased to about 50%. In addition, after long-term expose under UV light, no filtration efficiency decrease was observed in nanofiber membrane, which provide a suitable way to disinfect the potential carried virus. This work successfully achieved the daily disinfection and reuse of masks, which effectively alleviate the shortage of masks during this special period.

electrostatic dominated aerosol rejection mechanism of meltblown fabrics prevents the 18 mask from maintaining the desired protective effect after the static charge degradation. 19 Herein, novel reusable masks with high aerosols rejection efficiency were fabricated by 20 the introduction of spider-web bionic nanofiber membrane (nano cobweb-biomimetic 21 membrane). The reuse stability of meltblown and nanofiber membrane mask was 22 separately evaluated by infiltrating water, 75% alcohol solution, and exposing under 23 ultraviolet (UV) light. After the water immersion test, the filtration efficiency of 24 meltblown mask was decreased to about 79%, while the nanofiber membrane was 25 maintained at 99%. The same phenomenon could be observed after the 75% alcohol 26 treatment, a high filtration efficiency of 99% was maintained in nanofiber membrane, 27 but obvious negative effect was observed in meltblown mask, which decreased to about 28 50%. In addition, after long-term expose under UV light, no filtration efficiency 29 decrease was observed in nanofiber membrane, which provide a suitable way to 30 disinfect the potential carried virus. This work successfully achieved the daily 31 disinfection and reuse of masks, which effectively alleviate the shortage of masks 32 during this special period. The coronavirus disease 2019 (COVID-19) pandemic [1] [2] [3] [4] was first detected and 37 reported in Dec. 2019, which has spread in more than 200 countries around the world, 38 and has caused more than 23.5 million cases diagnosed (24,Aug., 2020).It has been 39 confirmed that the droplets/aerosol released by breathes, coughs, or sneezes of the 40 patients carry a large amount of viruses, which are highly infectious [5, 6] protect people from being infection. 49 The filter materials of the masks mainly include cotton gauze, polypropylene, 50 etc. [14] . In speak of cotton gauze masks, due to the large fiber diameter, the number of 51 gauze layers was increased to improve the filtration efficiency, resulting in a higher 52 breath resistance and poor thermal and wet comfort performance [15] . Therefore, 53 meltblown fibers with static charge was invented and employed to reconcile the aerosol 54 interception efficiency and air permeability [16] [17] [18] . Compared with cotton gauze masks, 55 meltblown fibers masks exhibit higher aerosol interception efficiency with lower breath 56 resistance due to the electrostatic adsorption effect in aerosol filtration process [19] [20] [21] [22] . 57 However, the filtration performance of the meltblown fabrics may rapidly decline after 58 the degradation of electrostatic. Therefore, nanofiber membrane masks were proposed 59 and developed to fabricate the masks. The nanofiber membrane with its fiber diameter 60 tens to hundreds of nanometers is suitable for fine aerosols interception [23, 24] . The 61 higher specific surface area of nanofiber compared to microfiber provides more contact opportunity to aerosols and fiber [25] [26] [27] [28] . In addition, the diameter of nanofiber can be 63 controlled comparable with the mean free path of the air molecules (66 nm under 64 normal conditions), which means the non-zero of gas velocity on the nanofiber surface 65 due to the "slip" occurs. The "slip effect" can significantly reduce the drag force of gas 66 flow and resulting in a lower filtration resistance. Therefore, nanofiber membrane can 67 break the trade-off effect between filtration efficiency and gas permeability [29] . 68 In this work, the protective performance of the masks prepared by the meltblown 69 fabrics and nanofiber membrane (nano cobweb-biomimetic membrane) was evaluated 70 in detail. The reusability of the two kind masks were investigated by testing the 71 filtration performance before and after disinfection of 75% alcohol and UV irradiation. 72 The three-day and seven-day long-term filtration performance were also performed to 73 verify the reusability of masks. The filtration and interception mechanisms for aerosols 74 of the masks were proposed. This paper will provide general public with an overall 75 understanding of the filtration materials, and help them choose appropriate mask and 76 disinfecting masks with correct strategies. As shown in Fig. 3a , the meltblown fabrics and nano cobweb-biomimetic membrane operation for another two times. 106 The UV irradiation disinfection experiment was performed under UV light with a 107 wavelength of 254 nm, and a power of 8 W. The masks were exposed under UV light 108 for 10 min and then tested for filtration performance. Same as forementioned, three 109 times of irradiation treatment were performed to evaluate the reusability of the masks. To make an intuitive sense of the difference between meltblown fabrics, nanofiber 128 membrane and the aerosols, the microstructure of the corresponding samples were 129 obtained as shown in Fig.4 . The meltblown fabrics with diameter around 5-10 μm are 130 stacked one by one( Fig.4(a) ), while the nanofiber membrane existence much fine fibers 131 (50-100 nm) with node-fiber connected structure ( Fig. 4(b) ). The interwoven pores of results, the microstructure of the meltblown fabrics and nanofiber membrane still has 183 no significant change ( Fig. 7 (a, b) ), demonstrating both materials have good alcohol 184 tolerance. Fig. 7 (c) reveals that the aerosol filtration efficiency of meltblown fabrics 185 was sharply declined from 95% to ~59% after the first alcohol treatment cycle. 186 Subsequently, the further alcohol treatment has few effects on the filtration efficiency 187 of meltblown fabrics(~59% -~48%).The results (Table 2) Therefore, the masks were exposed under UV light to investigate the influence of UV 209 irradiation on the filtration efficiency. The SEM images in Fig. 9(a, b) show that the 210 fabrics and fibers of both materials are well maintained without any break or 211 microstructure changes. The filtration efficiency results ( Fig. 9 (c) ) show both the 212 masks possess a comparable stable filtration efficiency after UV irradiation for 3 cycles. 213 The electrostatic value of meltblown fabrics after treated with UV can maintained well, 214 which means UV irradiation has no effect on decrease the charge of the meltblown 215 fabrics. Compared with water or 75% alcohol treatment, ultraviolet irradiation may be nanofiber surface is non-zero due to the "slip". The "slip effect" significantly reduce 

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