In 2020, a sudden new crown epidemic swept the world, and masks became the most popular and sought-after commodity for a while. The phenomenon of “one mask is difficult to get” appeared in the domestic and foreign markets, and the price of masks continued to rise, and then larger and small. Small mask factories have sprung up. There are many kinds of masks on the market, and the quality is also uneven. As an effective tool to prevent the spread of bacteria and viruses, the quality of masks has attracted attention from all walks of life.
This paper aims at the performance differences of filtration efficiency, expiratory resistance, and inhalation resistance of salt particles of five kinds of masks, including cloth masks, disposable flat masks, KN95 masks with breathing valves, and KN95 masks without breathing valves., analyzed its material and structure, and studied the filtration efficiency, inhalation resistance, and exhalation resistance of masks of various structural types. Wish the research results can provide effective help for consumers to choose suitable masks.
Cloth masks are usually divided into two types. One is composed of an outer layer of woven fabric + an inner layer of knitted fabric, and the other is a layer of melted-blown non-woven fabric added to the two layers of fabric.
Disposable flat masks usually have a three-layer structure; the inner and outer layers are spunbond nonwovens, and the interlayer is melt-blown nonwovens.
For KN95 masks, regardless of whether there is a breathing valve or not, the material structure is relatively close, generally having a 4-layer or 5-layer structure. The difference of the 5-layer structure is mainly that the interlayer will have an additional layer of melted-blown nonwoven fabric.
For the filtering effect, exhalation, and inhalation resistance, different masks were tested and the following test results were obtained.
Results of filtration efficiency of different types of masks are shown as below.
The filtration efficiency the cloth mask without the melt-blown nonwoven interlayer can reach 25%.
And the cloth mask with melt-blown nonwoven interlayer has significantly improved the filtering effect, and the result can reach 95%. The filtering efficiency of a disposable flat mask containing melt-blown nonwoven interlayer can also reach 95%.
For KN95 masks, the interlayer material contains hot air cotton and melt-blown non-woven fabrics, and the filtration efficiency of salt particles exceeds 97%; since the breathing valve itself is one-way, whether it is equipped with a breathing valve has little effect on the filtering effect of salt particles. However, the more layers containing melt-blown nonwovens, the better the filtration effect of the mask. The filtration efficiency of KN95 masks (samples 4 and 5) containing 2 layers of melt-blown nonwovens can reach more than 99%. To sum up, it can be seen that melt-blown nonwovens have a strong effect on salt particles. The filtration efficiency will have a very direct impact.
Inspiratory resistance results of different types of masks are shown as below.
Inhalation resistance of cloth masks without melt-blown nonwovens can reach 100 Pa.
The inhalation resistance of the cloth mask containing the melt-blown nonwoven in the interlayer is significantly increased, which can reach 130 Pa.
The inhalation resistance of the disposable flat mask is comparable to that of the cloth mask containing the melt-blown non-woven fabric in the interlayer; because the negative pressure of the breathing valve during inhalation will automatically close the valve to avoid inhaling external pollutants, so whether to wear
The breathing valve does not have much effect on the inspiratory resistance of the KN95 mask.
However, as the number of layers of melt-blown nonwovens increases, the suction resistance will increase significantly, and the suction resistance when a layer of melt-blown nonwovens is contained exceeds 150 Pa.
The suction resistance will increase to 250 Pa when two layers of melt-blown nonwovens are included. It can be seen that the melt-blown nonwovens will have a significant impact on the suction resistance.
Expiratory resistance results of different types of masks are shown as below.
The exhalation resistance of cloth masks without melt-blown nonwovens is below 100 Pa, while the exhalation resistance of cloth masks with a layer of melt-blown nonwovens in the interlayer will increase to 130 Pa, and those with a layer of melt-blown nonwovens The expiratory resistance of the disposable flat mask is close to.
The exhalation resistance of the KN95 mask with a breathing valve is smaller than that of a cloth mask with a layer of melt-blown nonwoven fabric and a disposable flat mask, which can only reach 80 Pa. This is due to the positive effect of the breathing valve when exhaling. The pressure can blow the valve plate open to quickly discharge the exhaust gas from the body.
KN95 mask without breathing valve, the exhalation resistance will be greatly increased.
Exhalation resistance up to 130 Pa with a layer of melt-blown nonwoven.
The exhalation resistance increases to 190 Pa with two layers of melt-blown nonwoven. It can be seen that the melt-blown nonwovens also have a significant impact on the exhalation resistance.
The results show that the melt-blown nonwovens have a direct impact on the filtration efficiency of salty particulate matter, and the filtration efficiency with the addition of melt-blown nonwoven interlayer masks exceeds 95%;A layer of melt-blown nonwoven mask has good filtering effect and relatively small inhalation and exhalation resistance, which can make consumers have good comfort; KN95 mask without breathing valve has good filtering effect, but wearing comfort is the worst among the 4 masks.