How to ensure melt blown nonwoven fabric filtration efficiency
Melt blown non-woven fabric is the core filter material of mask, which is mainly determined by the filtration mechanism of melt blown filter material, which is mainly divided into mechanical barrier and electrostatic adsorption.
1、 Mechanical barrier
Mechanical barrier has the following conditions:
1. Droplets with particle size greater than 5um in the air can be blocked by filter materials.
2. When the diameter of micro dust is less than 3um, the micro dust is mechanically intercepted by the curved channel fiber layer in the mask filter material.
3. When the particle size and air velocity are large, the particles are captured due to the collision between inertia and fiber. When the particle size is small and the flow velocity is low, the particles are captured due to Brownian motion hitting the fiber.
2、 Electrostatic adsorption
In the production process of melt blown fabric, electret treatment is usually used to make the non-woven fabric carry more static electricity and have electrostatic adsorption. Electrostatic adsorption refers to the capture of dust bacteria and viruses through the Coulomb force of the charged fiber when the fiber of the filter material is charged.
There are two ways to improve the charge storage capacity of Electret Materials:
1. By improving the crystallinity and mechanical deformation of the material, the structure of the material is changed to form slender hole channels to prevent charge drift.
2. Charge trap is generated by introducing an additive with charge storage performance to capture charge.
3、 How to store mask meltblown cloth
Jingong fan has equipped roots blower for more than 250 melt blown cloth production lines. Many experience about how to store mask melt blown cloth found out by customers in production and transportation will be popularized. Here, you can find brocade workers to buy roots blower, but don't find us for in-depth exchange of melt blown cloth production process parameters. It is clearly written in the articles that we know. In addition to being a professional of Roots blower, we are layman in melt blown cloth knowledge. Therefore, the content of this article is only for reference to avoid misleading due to parameter errors
It can be seen from the figure that the key to improving the filtering efficiency of masks lies in the electrostatic storage of melt blown non-woven fabrics. At the current flow speed of masks, the attenuation of static electricity is not considered enough (for example, half a month to the user after leaving the factory), while normal medical masks are valid for 6 months, while some masks in Japan are valid for 3 years.
Melt blown non-woven electret is very sensitive to environmental humidity. Jingong's customers have conducted an experiment. When they are stored at room temperature and high humidity (relative humidity greater than 95%) for 7 days, the sample surface potential of positive and negative corona charging samples has attenuated to 28% and 36% of the initial value respectively. At this time, because the melt blown non-woven fabric has an open structure, its specific surface area is large and its contact surface with the surrounding environment is larger, which makes it more sensitive to water vapor, corrosive gas and anisotropic charged particles in the environment. At the same time, the corona charging system can only produce ion charges with low beam energy, and most of the charges injected in the charging process are deposited on the near surface layer of the fabric surface fiber. When the samples are stored or work in high humidity environment, a large amount of charge loss is caused by the compensation effect of polar groups in water molecules and anisotropic ions in the atmosphere on the high concentration surface charge on the fiber. Therefore, the high humidity environment must be avoided during the transportation and storage of melt blown cloth