Under the epidemic situation, not only schools at all levels have started online teaching. With the help of a strong Internet platform, all kinds of live broadcast, online courses and online training in industry enterprises are also surging, which plays an important role in improving the ability of enterprises, maintaining customer base, ensuring operation and opening up new channels. "Textile and clothing weekly" opened the "micro lesson" column in WeChat official account. Welcome everyone to join the online class and enhance it together.
Pull together in times of trouble, novel coronavirus pneumonia, Donghua University's Textile Institute has invited the professors, counselors and epidemic prevention students to bring online cloud lessons.
In this issue, let's welcome Huang Chen, a teacher from the Department of Nonwovens Materials and engineering, Textile College of Donghua University, to give you the first lesson of "textile power in epidemic prevention and control"! Come and have a look!
Produced by Dingxin forum ideological and political micro course
Here are the highlights of this issue
Textile power in epidemic prevention and control
This time, the epidemic caused by the infection of pneumonia by the new coronavirus has had a great impact on everyone's life safety and the economic development of our country. I believe that the students, like me, have had a very curtily winter vacation. Fortunately, the network is developed now, so that I can share some information about scientific epidemic prevention and nonwovens for protection with you at the same time Knowledge of materials - most bacteria and viruses will spread through droplets, so the so-called droplet is the saliva that flies into the air. So for ordinary people, the most effective way to prevent virus infection is to wear masks when going out. When it comes to masks, they are inseparable with our textile materials, especially nonwoven materials.
Nonwovens in respirators
The mask is mainly composed of surface layer, middle core layer, inner layer, elastic band and nose clip. The surface layer is the one exposed to the outside, with waterproof effect. The middle core layer plays a core protective role, which can effectively prevent the penetration of bacteria, viruses and other micro particles; the inner layer is the layer contacting with our skin, that is, the mouth and nose. The surface layer and the inner layer, i.e. the inner and outer surfaces, are composed of spunbond nonwovens, while the middle layer is melt blown nonwovens.
Structure comparison between spunbond and melt blown fabrics
The structure of spunbond nonwovens is obviously different from that of melt blown nonwovens. It can be seen from the microscope photos that the fiber diameter of spunbond nonwovens is obviously larger than that of melt blown coarse spunbond fibers after being magnified 1000 times. The diameter of the former is generally 15-40 microns while that of the melt blown fibers is only 1-5 microns.
Because the melt blown fiber is so thin, the holes between the fiber and the fiber are correspondingly smaller, so many particles can be blocked by the melt blown cloth. However, it is not enough to intercept particles, bacteria and viruses only by the holes formed between the melt blown cloth fibers. Because these objects need to be intercepted, their sizes are much smaller than the holes of the melt blown cloth. When they pass through the melt blown cloth, they have a great chance to penetrate these holes and become a fish through the net. So can we make the melt blown cloth tighter and denser or replace it with materials with finer fiber diameter?
The idea of intercepting particles, bacteria and viruses makes sense. The smaller the hole, the more likely it is to intercept them. But for masks, in addition to the protective effect, there is also a very important indicator - the resistance of exhalation and inhalation. If we blindly make the hole smaller and the material denser and tighter, even though the protective effect is improved, the resistance of breathing will also increase significantly. It is estimated that such masks will not be worn for a long time, and we will be out of breath.
Electrostatic adsorption effect of melt blown cloth
In order to improve the protective effect without increasing the discomfort of exhalation and inhalation, we usually conduct electret treatment for the melt blown cloth. The so-called "electret" refers to the use of special technology to make the melt blown cloth fiber with a large number of positive charges, and the use of the familiar physical effect of "electrostatic adsorption" to catch fine particles. The melt blown cloth fiber before electret is for particles Particles have a certain adsorption, but after electret we can see a large number of fine particles adsorbed on the surface of the fiber. When the virus passes through the melt blown cloth, although our pores are much larger than the size of the virus, as long as the virus is slightly close to these fibers, it will be firmly adsorbed on the fibers by static electricity, so the mask can protect us from the infection of the virus.
Nonwovens in surgical clothing and protective clothing
In addition to masks, we also use a lot of Nonwovens in the protective clothing worn by our medical staff, among which SMS Nonwovens are more famous, that is, "English" spunbond melt blown spunbond non manufacturing materials. In this kind of material, two layers of S layer, i.e. spunbond layer, can play a very good role in protection and waterproof. The m layer uses its small hole to prevent the blood and body fluid of the patient from permeating through the protective clothing, so as to ensure the safety of the medical staff. Besides SMS, Tyvek is also widely used in the protective clothing, which is a kind of polyethylene flash spinning non-woven material. This kind of material fiber The dimension is also very fine, the fiber diameter is between 1-3 microns, which is similar to the melt blown cloth, so it can also play a good role in waterproof and isolation. Compared with the melt blown cloth, the strength of this kind of material is much higher, so there is no need for the S layer, that is, the spunbond layer to protect it.
Performance of protective material finishing
In protective clothing, besides nonwovens, we also need to use some finishing, such as the very famous "three repellents and one anti-static", that is, water repellent, blood repellent, alcohol repellent and anti-static finishing. After such finishing, the protective performance of protective clothing can be further increased, and the wearing comfort has also been greatly improved. In addition, nonwovens and microporous air permeable membrane are usually used in protective clothing. These processes greatly guarantee the comfort and protection of protective clothing, and none of them is necessary.
