The melt blown cloth burns smokeless without coke, and some other fake masks with napkins burn with smoke and coke. Therefore, the authenticity of masks can be distinguished?
The mask with good protective effect is usually composed of three layers of materials, the inner and outer layers are polypropylene spunbonded nonwovens, and the middle layer is polypropylene melt blown nonwovens. Melt blown nonwovens are composed of ultra-fine polypropylene fibers, which pass through the electrostatic electret. When the air passes through the mask, the melt blown layer captures the fine particles and droplets in the air through inertial collision, interception and diffusion, especially the mechanism of electrostatic attraction, so as to prevent the invasion of viruses.
There are some fake masks on the market. The material in the middle layer is napkin. Napkin wood pulp fiber can not be charged by electrostatic electret, which can not effectively filter the fine particles in the air. On the other hand, the wood pulp fiber in the napkin is hydrophilic and hygroscopic. When the mask wearer inhales air, some droplets are blocked on the surface of the mask. However, they will penetrate inward through the hydrophilicity of the napkin. Therefore, the middle layer is a fake mask of napkin, which can not protect against virus invasion.
The raw material of napkin is wood pulp fiber, which is extracted from trees. Napkins can be ignited by fire. When burning, there is the burning smell of smoke and wood, and finally a small amount of ash will be formed. Polypropylene spunbonded and melt blown nonwovens are completely different from napkins. They are made of polypropylene and are extracted from petroleum. When a flame is used to burn spunbonded and melt blown nonwovens, it will shrink, melt and form droplets, and will produce the smell of smoke and burning plastics.
However, there are many forms of masks with poor protective effect. For example, the intermediate layer does not use melt blown nonwovens, but ordinary spunbonded nonwovens. The fiber diameter of spunbonded nonwovens is larger than that of melt blown nonwovens, and the pore size in the fiber web is relatively large, so it is unable to effectively filter out the fine particles and droplets in the air.
Because spunbonded and melt blown nonwovens are made of polypropylene, it is difficult for ordinary people to distinguish melt blown and spunbonded nonwovens by combustion method. Therefore, burning smoke and burning smell can not distinguish the authenticity of protective masks.
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