Since novel coronavirus pneumonia outbreak grow with each passing day, the demand for mask has been increasing day by day, and more than 3000 enterprises in the country have added masks. As the key material of mask filtration, the melt blown cloth with fiber diameter only one thirtieth of hair can be regarded as the "heart" of medical surgical mask and kn95 mask. The supply is very tight, and the market price has doubled a dozen times, which can be said to be "one cloth is hard to find".
In order to alleviate the shortage of melt blown cloth in the current market, the Institute of membrane science and technology, Nanjing University of technology, gave full play to its professional advantages, developed a new type of filter material - Nano arachnoid biomimetic membrane, and applied it to the production of high-performance mask with membrane technology achievements to shoulder the mission of "epidemic".
Magic nano arachnoid biomimetic membrane material
The diameter of nano arachnoid biomimetic membrane fibers is in the range of 100-200 nm, and the fibers are staggered with each other to form a three-dimensional arachnoid network structure, and the size of the micropores can be controlled in the range of 0.1-0.5 μ M. "Compared with the melt blown materials with disordered fiber stacking and a diameter of more than 1000 nm, nano arachnoid biomimetic membrane has the advantages of high porosity, small pore size, low filtration resistance and high filtration accuracy." Said Zhong Zhaoxiang, a professor in the Department of membrane science, School of chemical engineering, Nanjing University of technology.
Generally, there are a large number of fine particles with positive and negative charges in the air. When these charged particles in the air pass through the vicinity of the electret, they will be strongly adsorbed on the electret fiber. Meanwhile, the uncharged particles will be polarized by induction in the electric field formed by the electret, and will also be adsorbed on the fiber. The traditional melt blown material has a large aperture, so it needs to add static electricity to improve the filtration efficiency. However, the static electricity is affected by the temperature and humidity in the environment, and it will fail in a short time, so the filtration efficiency is rapidly reduced, so the medical mask produced by the traditional melt blown cloth can only be used once in the market.
According to Zhong Zhaoxiang, nano arachnoid biomimetic membrane materials have the characteristics of high porosity, small pore size, low filtration resistance and high filtration accuracy. It can effectively filter more than 99% of non oil particles, effectively intercept various solid aerosols, droplets and viruses, without the need to worry about the problem of low filtration efficiency in case of liquid, and has good air permeability, and will not produce the discomfort of inhalation.
Overcome the obstacles of water washing and alcohol disinfection
At present, most of the medical surgical masks on the market are disposable, with a maximum use time of four hours. Although kn95 masks have a longer use time, they cannot be used repeatedly for a long time. This is because once the melt blown material adsorbs pollutants by charging, it is easy to have static neutralization phenomenon when encountering water, which will reduce the filtering efficiency of the mask, so the mask produced by melt blown cloth cannot be reused after ordinary cleaning.
"Nano arachnoid biomimetic membrane material has small pore diameter, which mainly intercepts pollutants through physical action, so there is no need to worry about the reduction of liquid efficiency." Wu Junwei, a doctoral student of Zhong Zhaoxiang's team, said that after the team researchers soaked the membrane materials in water and 75% alcohol for many times, the filtration efficiency was not affected, and they all kept above 99%, indicating that the membrane materials mask can be washed with water or sterilized with alcohol and reused, which greatly increased the utilization rate of the mask.
According to Wu Junwei, their multiple comparative experiments on service life, reusability and air permeability show that as a new type of filter material, nano arachnoid biomimetic membrane material has more excellent retention and air permeability than traditional melt blown materials, so it can be reused and has a longer service life.
It can also be used for medical protective clothing and air purifier
According to reports, the nano arachnoid biomimetic membrane material developed by the membrane Department of Nanjing University of technology can be used not only for making masks, but also for medical protective clothing, air purifier and other fields.
Zhongzhaoxiang said that the protective clothing made of nano arachnoid biomimetic membrane material has good antibacterial and water repellent performance and is the highest level of medical protective clothing. Its characteristic is that the sweat gas of human body can radiate outwards, but the water and bacteria virus outside can't enter. "The nano arachnoid biomimetic membrane material has about 1 billion pores per square centimeter, with porosity of more than 90%. The pore size is about 0.2 μ m, which is one thousandth of the diameter of water droplets, but about 700 times larger than the size of water vapor molecules. If liquid water can't come in, sweat gas can come out, so as to achieve excellent waterproof and moisture permeability. "
In the field of industry, the air purification membrane modified by double drainage has been used for ultra-low emission control of smoke and dust, and more than 100 sets of engineering equipment have been popularized and applied, generating economic benefits of more than 2 billion yuan. At present, air purification membrane materials and membrane masks have been used in hundreds of units, providing a strong guarantee for the staff who adhere to the front line of epidemic prevention.
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Source: China textile net
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