The melt-blown material is extruded by heating and then ejected by hot air through the fine hole of the nozzle. Micron or even submicron fibers are formed under the traction and stretching of hot wind. The melt-blown filter membrane commonly used in face masks is 25g of melt-blown material. Before the electrostatic electret treatment, the filtration efficiency of melt-blown materials is relatively low, about 30% to 40% of the aerosol filtration performance.
If electret masterbatch is added to the spinning PP masterbatch, the filtration performance of the melt-blown cloth material can be greatly improved after electrostatic treatment, and even the single-layer melt-blown material can achieve more than 95% particle filtration performance.But the electrostatic electret process of each manufacturer is different, therefore, the electrostatic retention capacity of melt-blown cloth is not the same.The filtration performance of most electret materials declines rapidly after the electret treatment.
Therefore, most of the domestic melt-blown material filtration performance stability is very poor. More than 90% of the melt-blown cloth filtration performance in 30%-90% of the filtration efficiency, so the quality is uneven.Mask manufacturers can easily buy fake mask filters because they don't know the technology. This is why many of the masks exported domestically are substandard. The main reason is the instability of the core filter material.
Another kind of water electret process can ensure that the electret on polypropylene is permanent, the electric field distribution is uniform, the capture ability is strong, is a relatively mature technology for the preparation of high efficiency and low resistance melt-blown materials. The water electret process can achieve stable N95 material properties at a lower gram weight. But the domestic water electret equipment is not much, the production capacity is also relatively low, in addition to the operating cost of equipment is also relatively high. Therefore, there is a limited amount of melt-blown materials that can satisfy the N95 properties in China. On the market a lot of melt-blown cloth factory take BFE95% melt-blown material as N95 material sale, cause a lot of face mask manufacturer who do not understand the market is deceived.