Structure Of Medical Mask
Medical masks are generally composed of melt-blown cloth, non-woven fabric, mask belt, and nose clip. The outer layer and inner layer are made of non-woven fabric, and the middle layer is made of melt-blown cloth:
①The outer layer is made of water-resistant material, which can block splashes such as saliva;
②The main material of the middle layer is polypropylene, which can block and filter tiny particles, such as bacteria and viruses;
③The inner layer is made of skin-friendly and absorbent material so that people wearing masks will not feel uncomfortable because of wearing masks;
④The nose clip can make the mask close to the skin to improve the sealing performance, and the mask can be unfolded up and down to cover the entire nose and mouth so that the inhalation of air needs to be blocked and filtered by the mask.
The Filter Material
The main filter material is polypropylene melt-blown cloth, which is a kind of ultra-fine electrostatic fiber cloth. Due to the electrostatic effect, it can capture dust, and droplets containing various viruses can be adsorbed on the surface of the melt-blown cloth after it approaches the polypropylene melt-blown cloth, can not go through.
Meltblown filtration levels suitable for flat masks are: ordinary, BFE95 (filtration efficiency 95%), BFE99 (filtration efficiency 99%), VFE95 (filtration efficiency 99%), PFE95 (filtration efficiency 99%), KN90 (filtration efficiency 90%) . Melt blown cloth generally chooses 20 grams of weight. The higher the weight, the better the protective filtering effect. Of course, if there are too many layers of non-woven fabric, the mask will be harder, while too many layers of melt-blown will make breathing more difficult.
The Working Principle Of Medical Mask Filter Material
1.Diffusion deposition: Brownian motion of particles diffuses and shifts to filter fibers, and is absorbed by molecular gravity. It is easiest to capture small-scale particles, fine fibers and low-speed particles.
2.Retention of deposition: larger particles moving with the airflow are retained by the mechanical sieving effect of the filter material. The ratio of the particle diameter to the diameter of the filter membrane fiber affects the interception efficiency.
3.Inertial deposition: When particles pass through the curved mesh channel of the filter material, the particles escape from the airflow and hit the filter fiber due to inertia, and are trapped by molecular gravity. Large particles, high density and high speed have good interception effect.
4.Electrostatic attraction and deposition: The particles are deposited by the electrostatic action of the filter fiber.
The smaller the particles, the stronger the deposition effect of 1, 4; the larger the particles, the better the effect of 2, 3.