How is qualified melt-blown fabric for masks made?

Meltblown fabric is the 'heart' of a mask, serving as a filter. Do you know the intricacies involved in the production of meltblown fabric, from material selection to electrostatic charging, and standard testing? Today, our editor will guide you through the process of how qualified meltblown fabric for masks is made.

The raw material for melt-blown nonwoven fabric, specifically the dedicated material for melt-blown, is polypropylene with a high melt index. The higher the melt index of polypropylene, the finer the fibers melt-blown, resulting in a melt-blown nonwoven fabric with better filtration performance.

The melt-blown fabric serves as a filter. Its material consists of ultrafine polypropylene fibers randomly distributed and bonded together. It has a white, smooth, and soft appearance. The fiber fineness of the material ranges from 0.5 to 1.0 μm. The random distribution of fibers provides more opportunities for thermal bonding between fibers, thus endowing the melt-blown gas filter material with a larger specific surface area and a higher porosity (≥75%). After undergoing high-voltage electret filtration efficiency treatment, the melt-blown fabric exhibits characteristics such as low resistance, high efficiency, and high dust holding capacity.

To ensure smooth breathing while meeting protective requirements, qualified meltblown fabric undergoes an electret process. After electret treatment, the fiber surface carries a large amount of charge, which intercepts fine particulate matter through electrostatic adsorption. Primary electretization involves applying static electricity through an electric field, while the advanced method involves using pure water to imprint static electricity onto the material. The significant characteristics of meltblown are high efficiency and low resistance. Deviations in electrostatic charge and resistance affect the filtration efficiency of meltblown fabric, ultimately impacting the use of masks. The following classification is for reference:

(1) Characteristics of ordinary melt-blown fabric: no static electricity, high resistance, filtration efficiency of only 30-40%, and low price

(II) Characteristics of ordinary corona melt-blown fabric: static electricity, high resistance, general filtration efficiency up to 90% or more, moderate price

(III) Characteristics of Electret Electrostatic Melt-Blown Fabric: Low resistance, initial filtration efficiency up to 99% or more, and high price

In terms of testing standards, taking cup-shaped masks as an example, N95 (American standard NIOSH) and KN95 (national standard GB2626) are almost identical in terms of standards. The domestic GB2626 standard is customized based on the American NIOSH standard and the actual situation in China. N95-NIOSH / KN95-GB2626 / FFP2-CE-EN149: testing standards of the United States, China, and the European Union.

(1) Similarities: N95=KN95=FFP2, all have the same filtration efficiency, ≥95%. The respiratory resistance standards in China, the United States, and the European Union are similar. The test medium is sodium chloride. Both the Chinese and American standards use the TSI8130 testing equipment for testing. The test medium for FFP2 is naphtha.

(2) Differences: The national standard adds a mask air tightness test compared to the American standard, which is similar to the European standard CE-EN149. There are minor differences in the testing of masks with breathing valves: the American standard uses the cover film analysis method, while the national standard uses the cavity pressure loss method, which can be considered essentially the same. It is worth mentioning that the national standard includes a test requirement for the connection strength of mask straps: the ear straps or head straps must not break after being evenly pulled for 10 seconds under a tensile force of 10N to be considered qualified.

How to identify the authenticity of meltblown fabric? Here are some simple ways to distinguish: First, when exposed to fire, the meltblown layer will melt but not burn, whereas paper will burn. Second, the meltblown layer carries static electricity. If you tear it into strips, you can clearly feel the electrostatic adsorption effect, and you can also adsorb the strips onto stainless steel.

How many masks can be produced with one ton of meltblown nonwoven fabric? One ton of meltblown nonwoven fabric can produce approximately 1.05 million disposable masks without loss, 600,000 KN95 masks, and 400,000 medical N95 masks. The production output can be appropriately increased based on the actual production rate.