N95 masks: powerful 95% filtration efficiency
N95 masks can filter most influenza viruses, dust, pollen, smog, smoke in car exhaust, etc. The filtration efficiency must reach at least 95 %.
N stands for not resistant to oil, that is, not oil-proof, and 95 represents the filtration efficiency level when testing 0.3 micron particles.
With N95 mask with breathing valve
100 times magnification to see the melt-blown cloth of the mask
After cutting the N95 mask open, you can see Its internal structure mainly has three layers, among which the key layer that plays a blocking role is the melt-blown cloth currently sold on the market for 290,000/ton.
We magnified the melt-blown layer 100 times and observed the melt-blown cloth. We can see that the melt-blown cloth is composed of countless ultrafine fibers intersecting and overlapping each other. into a dense network.
Magnify 100 times (Mask melt-blown cloth , photographed by Olympus microscope)
Among them, the thickness of each fiber is about 1 to 5 microns, and the fibers are intricately connected, which can prevent dust, viruses and bacterial droplets. etc. while maintaining the holes for exhalation to pass through. Therefore, it not only meets the filtration efficiency but also meets the requirements of breathing resistance.
There is no harm without comparison. Let’s compare it with ordinary non-woven fabrics. Under the microscope, although the fibers look more uniform and beautiful, the diameter of the fibers is more than 20 microns, and the gaps are Much larger, with this, non-woven fabrics can effectively block viruses, bacteria and small particles of dust.
Magnification 100 times (ordinary non-woven fabric, photographed by Olympus microscope)
N95 mask cloth: static electricity addition (electret treatment)
The melt-blown layer of N95 mask has fine fibers that are not enough, and static electricity needs to be increased through electret discharge treatment. Within a certain range, the greater the external voltage (electret voltage), the more firmly the charges are bound, and therefore the higher the filtration efficiency.
Electret discharge treatment of melt-blown cloth
Electret treatment: Electret masterbatch
The surface charge of melt-blown cloth will decay over time. After adding electret masterbatch, the decay time is greatly extended. , with the appropriate increase in the amount of electret masterbatch added, the charge retention rate becomes longer, and the attenuation rates of different electret masterbatch formulas are different.
Remarks: From the literature, used to illustrate the problem of charge attenuation
Electret masterbatch (usually added 2-3%), separates the positive and negative charges of polypropylene microfibers and fixes them, allowing the charges to be stored for a longer period of time.
Polarized fiber
There are very few electret masterbatch manufacturers. Most of them are masterbatch factories that support melt-blown cloth. The scale is usually small.
We have accumulated experience in long-term production. We have conducted a large number of groping tests on the formula from additives, basic resin selection, granulation temperature, screw combination, melt finger control, additive content, etc., and combined with electret treatment, optimization In order to test the filtration performance, filtration resistance and other indicators, the melt-blown cloth is also placed for half a year, 1 year, 2 years or even longer before testing the filtration performance and other indicators.
Through melt-blown fabric factories and customer channels, we have collected electret masterbatch manufacturers with good feedback on the market. This is for reference only. The specific application is also related to the manufacturer’s melt-blown equipment, process and formula.
Table 1. Domestic electret masterbatch manufacturers (to be updated)
Maintenance of N95 masks – the natural enemy of static electricity
As time goes by, the electric charge behind the electret will weaken and the binding force will weaken and the electric charge will wander away. , the polarization effect is weakened. As time goes by, static electricity will slowly disappear, which is why N95 masks have a shelf life. The general shelf life is about five years. The biggest fear of N95 masks is water. The secret to maintaining them is to stay away from water.
During the protective process of N95 masks, particles are adsorbed and static electricity is consumed. Therefore, after using it for a period of time, a large number of particles are absorbed, the static electricity is consumed, and there is no additional static electricity to absorb particles. This is why used N95 masks cannot be reused.
Finally: It is precisely because of the intricacies of meltblown cloth fibers that N95 masks and medical surgical masks can block viruses and dust! Some criminals, in order to make huge profits, use extremely inferior, cheap, and substandard raw materials. Some even directly omit the most important melt-blown filter layer in the middle and replace it with ordinary non-woven fabrics.
Such masks do not filter viruses at all and may cause harm to the body. Therefore, when we purchase masks, we must pay attention to whether there is meltblown cloth inside the mask.
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