Melt blown fabric is the core filter material of mask, which is mainly determined by the filter mechanism of melt spray filter material, mainly divided into mechanical barrier, electrostatic adsorption and electret treatment.
1. Mechanical barrier
Mechanical barriers can be as follows:
A. Droplets with particle size greater than 5um in the air can be blocked out by filtration materials.
B. When the dust diameter is less than 3um, the dust is mechanically intercepted by the curved channel fiber layer in the mask filter material.
C. When the particle size and airflow velocity are both large, the particle is captured due to the collision between inertia and fiber; when the particle velocity is small and low, the particle is captured due to Brownian motion impacting on the fiber.
2. Electrostatic adsorption
Usually in the production process of molten spray cloth will be polar treatment, so that non-woven cloth with more electrostatic, with 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:
A. By improving the crystallinity and mechanical deformation of the material, the structure of the material will change and a long and thin hole channel will be formed to prevent charge drift.
B. Generate charge traps to capture charge by introducing additives with charge storage properties.
3. Standing pole processing
The key to improving the filter efficiency of masks lies in the electrostatic storage of melt blown nonwoven fabrics. At the current flow rate of masks, the electrostatic attenuation is not sufficient (for example, half a month after they leave the factory). However, normal medical masks are valid for 6 months, while some Japanese masks are valid for 3 years.
The electret of melt blown nonwoven fabric is very sensitive to ambient humidity.A customer once conducted an experiment. After being stored for 7 days under the condition of normal temperature and high humidity (relative humidity greater than 95%), the surface potential of positive and negative corona charging samples has attenuated to 28% and 36% of the initial value respectively.At this time because of melt-blown non-woven fabric has an open structure, the specific surface area is larger, more contact with the surrounding environment, make the moisture in the environment, corrosive gas, heterosexual charged particles, such as more sensitive, at the same time, the corona charging system can only produce low beam can ionic charge, charge injection in the process of charge most of the near surface layer was deposited on the cloth surface fibers.When the sample is stored or operated in a high humidity environment, a large amount of charge loss is caused due to the compensation effect of polar groups in water molecules and heteroions in the atmosphere to the high concentration surface charge on the fiber.Therefore, the high humidity environment must be avoided in the process of melting and spraying cloth transportation and storage.
The above is the analysis of the three reasons for the melt blown nonwoven fabric to ensure the filtration efficiency. I hope you will like it.We are a professional melt blown nonwoven manufacturer. If you have any purchase requirements, please do not hesitate to contact us immediately. We will send samples to you free of charge
Post time: Nov-07-2020