Most of N95 masks disinfection methods are wrong! Cui Yi this ACS Nano give you Weapon

As at Beijing at 21:00 on May 2020 on the 6th, the new crown pneumonia patients worldwide have totaled 3,751,966 people, and caused 259 209 deaths. Close droplet transmission, contact transmission and spread of aerosols are three main modes of transmission of the new crown pneumonia, and three modes of transmission are needed to reach the lungs through the respiratory tract of a new host, and then the formation of infection. Therefore, wearing a mask is the best way to reduce the risk of the sensor. Currently protective effect is better masks N95 masks, however, due to the raging global epidemic led to the surge in demand for N95 masks and N95 mask production supply chain is damaged due to a significant reduction in the current epidemic is serious country, N95 masks has become a luxury, there has been a lot of short supply situation. In order to alleviate this serious situation, even the US President Trump also recognized: to increase the number of N95 masks can be sterilized using masks! So, what disinfection method not only ensures that the protective effect of N95 masks, and conditions applicable to the majority of ordinary families do? 大部分N95口罩消毒方法都错了!崔屹这篇ACS Nano给你支招 To solve this problem, Stanford University professor Yi Cui research team gives the answer in the latest issue of \”ACS Nano\” in:

(1) a simple heat treatment (temperature between 75 ~ 100 ℃, time between 5 ~ 30min, the lower the temperature, the longer the processing time) can be well maintained masks N95 filtration efficiency (> 95%). The post-treatment 20 times (20 min) at a temperature of 85 ℃, humidity of 30% for filtration efficiency N95 masks still up 96.79%. (2) ultraviolet irradiation treatment (254 nm, 8W) N95 masks filtration efficiency may be maintained at a low condition number of cycles. When more than 10 times treatment cycles, began to significantly decrease the efficiency of the filter; after 20 treatments, N95 masks filtration efficiency of only 93%. (3) N95 masks directly immersed in a disinfecting solution will significantly reduce the filtering efficiency of the mask. As N95 mask after immersion in 75% alcohol out quickly, reducing the efficiency of filtration and drying, masks to 56.33%.

The study of anti-virus sterilization methods were several home test and evaluate, recommend N95 masks are given a preferred method of disinfection. In this period of rapid spread of the infection, to alleviate the shortage of N95 masks pressure has a positive role in promoting. The studyEntitled \”Can N95 Respirators Be Reused after Disinfection? How Many Times?\” Papers published in \”ACS Nano\”. (Link attached description) 大部分N95口罩消毒方法都错了!崔屹这篇ACS Nano给你支招

[N95 masks and protective structure Principle]

大部分N95口罩消毒方法都错了!崔屹这篇ACS Nano给你支招
FIG. 1. (A) N95 respirator interior multilayer structure appearance; (B) SEM image of a multilayer structure; (C) PP meltblown FIG high multiple SEM; (D) uncharged (left) and charged (right) PP meltblown particle barrier effect is a schematic diagram of [ 123] [123 define a test or standard] N95 of NaCl aerosol particles is 0.3 um to achieve> 95% barrier. N95 masks supported by a barrier layer (or protect) the upper and lower layers and the intermediate nonwoven microfiber meltblown PP composition, wherein, the core material is PP meltblown N95 respirator protection. It can be seen from SEM images, PP meltblown fibers is between 1 ~ 10um interposed composed by, while the middle there is a large gap, in order to ensure breathability mask. But the new crown virus only about the size of 150nm, then the N95 masks contain a large gap is how to effectively block the virus do? In fact, this is mainly derived from the highly charged surface of the fiber PP meltblown! Before assembly into a mask, meltblown fibers may be meltblown fabric and an inner surface of an electrostatic charge more enriched by rubbing or the like corona treatment step, the electrostatic charge may enhance adsorption of the mask of small particles. Thus, the disinfection process masks and body structure as long as the surface charge of the fiber without destroying its basic protective properties can be well maintained.
[the effects of different disinfection methods for N95 masks protective properties]

Figure 2. different disinfection methods affect protective properties of PP melt-blown fabric 大部分N95口罩消毒方法都错了!崔屹这篇ACS Nano给你支招
The author first several conventional disinfection method using the home / PP melt-blown cloth agent on the first treatment, the results shown in FIG. The authors found that the PP meltblown disinfectant solution (the experiment using the disinfectant alcohol and NaClO) in direct contact will be greatly reduced filtration efficiency meltblown, such as 75% alcohol solution to the post-processing filtering efficiency drops 56.33%. In a small pressure drop and the test described throughout the sterilization process sterilizing solution uncorrupted body structure meltblown fibers; therefore, this approach causes of meltblown filtration efficiency is decreased that the solvent molecules form the adsorption layer, an amount of electrostatic charge resulting in decreased meltblown fibers. Therefore, this directly with disinfectant disinfection method is not desirable N95 masks! On subsequent heat treatment is good disinfecting effect of steam treatment and UV processing cycle studies, we found that steam treatment meltblown filtration efficiency remains high and is preferably in the initial few cycles during several cycles later and A sharp decline. After the study the authors found that the water molecules are not prolonged contact with the meltblown fibers or the multi-contact but will not significantly reduce the effect of electrostatic charge on the fiber surface. Therefore, the authors next investigated the systematic process of heating temperature and humidity meltblown filtration performance.
FIG 3. (A) and (B) are 75 deg.] C and dried, water vapor, and post-treatment cycles UV meltblown filtration efficiency and pressure loss 大部分N95口罩消毒方法都错了!崔屹这篇ACS Nano给你支招
[123 ] 123] 123 Effect [[] 4. FIG different drying temperature and humidity on meltblown filtration efficiency and pressure drop of the

the results show that moisture meltblown filtration efficiency of the heating treatment is not too large effect, and the heating temperature at the time interval 75 ~ 100 ℃, several meltblown after the cycle test, filtration efficiency can be well maintained. After the treatment, for example, 20 times (20 min) at a temperature of 85 ℃, humidity of 30% for filtration efficiency N95 masks still up 96.79% [FIG. 4 (B) and (C)]. But will reduce the static charge content of the fiber temperature is too high, this may be a high temperature that the fiber polarization state to a relaxed state due to recovery. Finally, the authors studied the UV treatment on circulating meltblown filtration efficiency, it found that too much static charge cycle can lead to decreased amount of fiber, which led to decreased filtration efficiency. For example, after the 254 nm, ultraviolet radiation and other 8W processing cycle 20 times, meltblown filtration efficiency dropped to 93%, the N95 is lower than the standard.

大部分N95口罩消毒方法都错了!崔屹这篇ACS Nano给你支招
Effect of meltblown filtration efficiency of ultraviolet loop processing in FIG. 5.
[summary] 大部分N95口罩消毒方法都错了!崔屹这篇ACS Nano给你支招 The simple heatingProcessing (75 ~ 100 ℃, dry or wet environment) can effectively ensure filtration efficiency N95 masks, and through many cycles, filtration efficiency can still be well maintained. The use of disinfecting solution directly N95 masks disinfecting method can significantly reduce the amount of static charge meltblown, thereby greatly reducing the effect of the filter mask. And UV and short steam treatment does not significantly affect the amount of electrostatic charge and meltblown filtration efficiency N95 masks. Original link: https: //pubs.acs.org/doi/10.1021/acsnano.0c03597

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