What Is The Key To The Face Mask Protective Grade?–Melt-Blown Fabric
1.Definition And Use Of Melt-Blown Cloth
The Melt-blown cloth is the core material of the mask. Melt-blown cloth mainly uses polypropylene as the main raw material, and the fiber diameter can reach 1 to 5 microns. With many voids, fluffy structure and good fold resistance, the ultrafine fibers with unique capillary structure can increase the number and surface area of fibers per unit area, so that the melt-blown cloth has good filtering, shielding, heat insulation, and oil absorption. It can be used in the fields of air, liquid filtration materials, insulation materials, absorption materials, mask materials, thermal insulation materials, oil-absorbing materials, and wipers. Has many uses:
(1) Medical and sanitary cloths: surgical gowns, protective clothing, disinfecting cloths, KN95 masks, diapers, etc .;
(2) Fabrics for home decoration: wall coverings, tablecloths, bedsheets, bed covers, etc .;
(3) Cloth for clothing: lining, adhesive lining, flakes, shaped cotton, various synthetic leather base fabrics, etc .;
(4) Industrial fabrics: filter materials, insulating materials, cement bags, geotextiles, covering fabrics, etc .;
(5) Agricultural fabrics: crop protection fabrics, seedling raising fabrics, irrigation fabrics, thermal insulation curtains, etc .;
(6) Others: space cotton, thermal insulation, and sound insulation materials, linoleum, cigarette filter, tea bags, etc.
2. The Protective Effect Of Melt-Blown Cloth
Question: How do masks block viruses? How are melt-blown fabrics produced?
Answer: Mainly rely on the mechanical barrier and electrostatic adsorption of the melt-blown cloth in the mask.
The masks currently used for virus protection are basically non-woven fabrics. The mask fabrics are composed of spun-bonded non-woven fabrics and melt-blown nonwoven fabrics produced from polypropylene (PP) as raw materials. Medical masks are generally made of three layers of non-woven fabrics, as shown in Figure 1, that is, the structure of SMS (two layers of Slayer and one layer of M layer), which has a high strength of spun-bond nonwoven fabric (S) The performance of small vertical and horizontal strength difference and the high shielding and waterproof performance of melt-blown non-woven fabric (M) are concentrated on one material, forming a mask with strong waterproof performance, good air permeability and efficient isolation performance.
The materials of the “S” and “M” layers are as follows: S stands for the spun-bond layer (Spunbond), the fiber diameter is relatively thick, about 20 microns (μm), the outer layer S has the function of dust and water resistance, which can prevent flying The foam enters the mask, the inner layer S has a water-absorbing effect, which can absorb the moisture of the wearer’s mouth and nose, and the two layers of S the spun-bond layer support the entire non-woven fabric structure. The filtering effect of the SMS structure is shown in Figure 2.
The middle melt-blown layer M (Meltblown) is the most important barrier layer. It is a very fine and electrostatic melt-blown nonwoven fabric with a fiber diameter of about 2 microns (μm). Dust, bacteria, and viruses When the foam is close to this melt-blown non-woven fabric, it will be electrostatically attracted to the surface of the melt-blown fabric and cannot penetrate. Since the suspended particles such as dust are caught by the ultrafine electrostatic fibers, it is very difficult to separate due to cleaning, and water washing will destroy the electrostatic suction ability of the electrostatic, so this mask can only be used once.
3.The production process of melt-blown cloth:
1.The production process of melt-blown cloth
The melt-blown fabric does not look special, but the production process is very complicated. Its production process can be summarized into three major links: first, naphtha is extracted from petroleum, then chemically processed into polypropylene, and finally melt-blown. The general process is shown in Figure 3.
2. The production process of the melt-blown cloth
The production process of melt-blown cloth is mainly divided into three steps: melt extrusion, melt-blown process, and electret treatment. The specific flow diagram is shown in Figure 4. Here we focus on the electoral treatment.
Electret refers to a dielectric material with long-term charge storage function. It has the advantages of high efficiency, low flow resistance, antibacterial, and energy saving. On the basis of ensuring the physical impact barrier effect of conventional filter materials, electrostatic adsorption is added. The electret treatment makes the filter material fibers charged, combined with the dense characteristics of melt-blown ultrafine fiber materials, so a large number of electrodes are formed between the charged fibers. The charged fibers can not only attract most of the charged particles in the environment like a magnet, but also Part of the uncharged particles can be polarized, and then some pollutants with smaller particle size can be adsorbed. Even nano-scale substances such as viruses can be electrostatically adsorbed or blocked by charge repulsion.
The melt-blown cloth used in medical N95 or FFP2 masks must be electret treated. Sterile medical masks are sterilized with ethylene oxide. After sterilization, there will be residual ethylene oxide on the mask, which not only stimulates the respiratory tract but also causes carcinogens. The residual ethylene oxide must be released through the analysis method to reach the safe content standard. The entire standard process of analysis and disinfection takes 7 days to half a month.
4.The basis for detection of the melt-blown cloth:
1.According to the standard
FZ / T 64034-2014 spun-bond / melt blown / spun-bond (SMS) method nonwoven fabric
(1)Appearance quality inspection: fabric appearance, holes, impurities, odors, micropores, crystal points, frit, stiffness, unreinforced area, thin mesh, width deviation, color difference, joint quality
(2)Intrinsic quality testing: mass deviation rate per unit area, longitudinal breaking strength, transverse breaking strength, longitudinal and longitudinal breaking elongation, hydrostatic pressure, air permeability
(3)Detection of microbiological indicators: total number of bacterial colonies, total number of fungal colonies, coliforms, pathogenic pyogenic bacteria announcement