The Heart Of Masks - Meltblown Cloth

1. Introduction to melt blown non-woven fabric

Medical masks consist of at least three layers of non-woven fabric, among which the melt blown non-woven fabric located in the middle layer is the core "heart" of the mask's filtration function. It has outstanding adsorption and filtration capabilities and can block the spread of virus droplets.

2. Production process of melt blown fabric

The production process is similar to the common cotton candy production, which involves adding granulated sugar to the cotton candy machine. The granulated sugar is heated and dissolved into syrup, which is then blown out by hot air to form extremely fine fibers. Although the principle is similar, for the manufacturing of melt blown fabrics, an important process - polarization treatment - is required to meet medical protection standards. Below is a specific introduction:

Melt blown fabric uses molten polymers (such as polypropylene), which are sprayed out of molds with many small nozzles under high pressure. The production process of melt blown fabric is generally composed of a series of operations such as polymer dissolution, melt discharge, filtration and metering, spinning into a mesh, coiling, rolling, and applying static charges to the electrode, becoming the final melt blown fabric product.

3. How does meltblown cloth filter COVID-19?

With such a large gap in the melt blown cloth, how can we filter the COVID-19 with a size of about 100 nm in the environment?

Melt blown cloth fibers under scanning electron microscope, with a scale of 3 in the figure μ M

(1) The virus cannot exist independently, and its transmission routes mainly include secretions and sneezing droplets, which are about 5 microns in size

(2) One step in the production process of melt blown fabric is "polar treatment", which allows the polypropylene mesh fibers to carry a sufficient amount of charge. When virus containing droplets approach the melt blown fabric, they use the electrostatic effect to adsorb particles. The virus containing droplets are first blocked by crisscrossing fibers and firmly adsorbed onto the melt blown fabric by static electricity.

4. Electrostatic air purifier for dust removal

Through static electricity (a metal rod can often be found inside the air purifier of electrostatic dust removal, which is the "heart" of the machine. High voltage static electricity is generated by pressurizing this metal rod) to charge pollutants in the air. Then, a dust collection device is used to capture and adsorb charged particles of air dust, achieving the goal of purifying the air.

Simply put, it is to use the characteristic of electrostatic adsorption to firmly grasp dust and other substances in the air. However, for harmful gases such as formaldehyde, the effect of electrostatic adsorption is very limited.