Originally published as Those things about masks In the face of the sudden outbreak of the novel coronavirus, More and more people are aware of the important role of masks. So, these scientific knowledge about masks Do you know? Expand the full text How to choose a mask? In terms of design, according to the priority of the wearer's own protection ability (from high to low): N95 mask > surgical mask > ordinary medical mask > ordinary cotton mask. For the pneumonia caused by the novel coronavirus infection. There is an obvious barrier effect. surgical mask And Masks with 95% or more filtration of non-oily particles Such as N95, KN95, DS2, FFP2, etc. At present, medical masks in China are mainly divided into three types: the highest level of medical protective masks, the surgical mask commonly used in invasive operating environments such as operating rooms, and the general level of disposable medical masks. So why can masks stop the spread of the virus? What kind of material is it? We usually say that the mask is a non-woven material, non-woven is relative to textile cloth, that is, non-woven cloth, is composed of directional or random fibers. Specific to the mask, its raw materials are all Polypropylene (PP), medical masks are generally multi-layer structure, generally referred to as SMS structure. Little knowledge of chemistry Polypropylene (PP) is a colorless, odorless, non-toxic and translucent solid substance. It is a polymer formed by the addition polymerization of propylene. The molecular formula is- [CH2CH (CH3)] n-. Polypropylene is widely used in the production of fiber products such as clothing, blankets, medical equipment, automobiles, bicycles,Medical Quickly Delivery Antivirus Coverall, parts, pipelines, chemical containers, and also in the packaging of food and medicine. From the point of view of mask materials, polypropylene high melt index non-woven fabric is the best choice to produce polypropylene products with melt mass flow rate of 33-41 G/min, which meets the standard of polypropylene non-woven fabric. The non-woven fabric produced by the polypropylene non-woven fabric special material can be used for medical and health products such as disposable surgical gowns, sheets, masks, covers,Medical Full Body Coverall, liquid absorption pads and the like. Among them, the non-woven mask is made of two layers of fiber non-woven fabrics specially used for medical and health care, and a layer of filter and anti-bacterial spray cloth with more than 99.999% filter is added in the middle, which is welded by ultrasonic wave. Here are some anti-virus medical masks: The main masks that can protect against viruses are surgical mask and N95 mask. The national standard YY 0469-2004 "Technical Requirements for surgical mask" stipulates that the important technical indicators that surgical mask must meet include filtration efficiency, bacterial filtration efficiency and respiratory resistance: Filtration efficiency: under the condition of air flow of (30 ± 2) L/min, the filtration efficiency of sodium chloride aerosol with aerodynamic median diameter of (0.24 ± 0.06) μm is not less than 30%; Bacterial filtration efficiency: under specified conditions, the filtration efficiency of Staphylococcus aureus aerosol with an average particle diameter of (3 ± 0.3) μm shall not be less than 95%; Respiratory resistance: under the condition of filtration efficiency flow, the inspiratory resistance shall not exceed 49 Pa, and the expiratory resistance shall not exceed 29.4 Pa. The second standard to ensure the filtration effect of bacteria is that the filtration efficiency of Staphylococcus aureus bacterial aerosol is not less than 95%, which is the origin of the concept of N95. Therefore, although the N95 mask is not a medical mask, it meets the standard of 95% filtration efficiency, and can better fit the human face, so it can also play a very good role in virus prevention. The main material that brings virus filtration to these two kinds of masks is the extremely fine and electrostatic inner filter cloth, melt-blown non-woven fabric. The main material of melt-blown non-woven fabric is polypropylene, which is a kind of ultra-fine electrostatic fiber cloth that can capture dust. When droplets containing pneumonia virus are close to melt-blown non-woven fabrics, they will be electrostatically adsorbed on the surface of non-woven fabrics and can not penetrate. This is how the material keeps out germs.
After the dust is captured by the superfine electrostatic fibers, 3 Ply Disposable Protective Face Mask ,Quickly Delivery Disposable Protective Clothing, it is not easy to be separated by cleaning, and the dust collection ability of the electrostatic will be destroyed by washing. Therefore, this kind of mask can only be used once. Melt-blown filtration levels suitable for flat masks are: normal, BFE95 (95%), BFE99 (99%), VFE95 (99%), PFE95 (99 percent), KN90 (90 percent). The surgical mask is generally made of three layers of non-woven fabrics. The material is spunbond non-woven fabric + melt-blown non-woven fabric + spunbond non-woven fabric. One layer of staple fiber can also be used to improve skin touch, that is, ES hot-rolled non-woven fabric + melt-blown non-woven fabric + spunbonded non-woven fabric. The outer layer of the mask has an anti-droplet design, and the middle layer filters and absorbs moisture. Melt-blown nonwovens generally weigh 20 grams. The N95 cup-shaped mask is composed of needle-punched cotton, melt-blown cloth, and non-woven fabric. The melt-blown cloth usually weighs 40 grams or more, plus the thickness of needle-punched cotton, so it looks thicker than the flat mask, and its protective effect can reach at least 95%. Several layers of masks are not stipulated in the national standard GB/T 32610 for masks. If it is a medical mask, it should be at least three layers, that is, SMS (two layers of S and one layer of M). At present, the highest number of layers in China is five layers, that is, SMMMS (two layers of S and three layers of M). It is not difficult to make masks, but it is more difficult to make SMMMS cloth. The price of an imported non-woven equipment is hundreds of millions of yuan. The S here represents the Spunbond layer, and its fiber diameter is relatively thick, about 20 microns (μm). The main function of the two S spunbond layers is to support the whole non-woven fabric structure, and it does not have much effect on the barrier. The most important thing inside the mask is the barrier layer or meltblown layer M (Meltblown). The fiber diameter of the meltblown layer is relatively thin, about 2 microns (μm), so it is only one tenth of the diameter of the spunbond layer, which plays a vital role in preventing bacteria and blood penetration. If the S spunbond layer is too much, the mask will be harder, and if the melt-blown layer M is too much, it will be more difficult to breathe. Therefore, the isolation effect of the mask can be judged from the difficulty of breathing. The more difficult it is to breathe, the better the isolation effect will be. However, if the M layer becomes a film, it will be basically airtight. The virus is blocked, but people can not breathe. So, this is also a technical problem. In order to better illustrate the problem, we will make a comparison between spunbond layer S fiber, meltblown layer M fiber and hair as follows. 1/3 of the diameter of hair is close to that of spunbond layer fiber, while 1/30 of the diameter of hair is close to that of meltblown layer M fiber. Of course, R & D personnel are still developing thinner fibers to ensure better antibacterial barrier. As mentioned earlier, the thinner the M layer is, the more it can block the entry of bacteria and other tiny particles, such as N95, which means that under normal circumstances, 95% of the tiny particles (0.3 microns) can be blocked, according to the national standard GB/T 19083 for medical protective masks, when the gas flow is 85 L/min. The filtering efficiency of the mask for non-oily particles shall meet the requirements in the following table: Table 1: Filtration Grade of Medical Protective Mask From the above explanation, N95 is actually a five-layer mask made of polypropylene non-woven SMMMS, which can filter 95% of fine particles. Having said so much theoretical content, how is the mask made? Let's watch a video together. At present, the new coronavirus epidemic is severe, and the supply of masks is in short supply in many places. The upstream refining and chemical enterprises and downstream production enterprises of masks are working overtime to increase production and fight against this war without smoke of gunpowder. Finally,Full Body Disposable Coverall, I implore everyone: Wear masks and do a good job of protection. This is not only for their own protection, It is also a contribution to the prevention and control of the epidemic. Everyone is a line of defense. Keep the virus out of the mask. The devil of the epidemic will eventually be completely covered. "If you are watching, please click and then go." Return to Sohu to see more. Responsible Editor:. zjyuan-group.com