June 26, 2022

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COVID-19: Quality Issues About Non-woven Fabric of Masks

COVID-19: Quality Issues About Non-woven Fabric of Masks

COVID-19: Quality Issues About Non-woven Fabric of Masks. If the non-woven fabric is unqualified, do these problems occur in production?  The non-woven fabrics produced by many manufacturers are always unqualified. Sometimes the two sides are thin and the middle is thick, or the left side is thin, or the hardness is uneven. The main reason is that the following aspects are not done in the production process. In place.

COVID-19: Quality Issues About Non-woven Fabric of Masks

1. Under the same processing conditions, why does the non-woven fabric have uneven thickness?

(1) Uneven blending of low-melting fiber and conventional fiber:

Different fibers have different cohesive forces. Generally speaking, low-melting-point fibers have greater cohesion than conventional fibers and are less easy to disperse. If the low-melting-point fibers are unevenly dispersed, the low-melting-point fiber content is less. Because it is unable to form a sufficient network structure, the non-woven fabric is thinner and thicker than where the content of low-melting fiber is high.

(2) Incomplete melting of low-melting fiber:

The incomplete melting of low-melting fiber is mainly due to insufficient temperature. For non-woven fabrics with low basis weight, it is usually not easy to cause insufficient temperature. However, for products with high basis weight and high thickness, special attention should be paid to whether it is sufficient. The non-woven fabric at the edge has enough heat, the non-woven fabric is usually thicker, the non-woven fabric at the middle part, because the heat is not easy to form a thinner non-woven fabric,

(3) High shrinkage rate of fiber:

Whether it is a conventional fiber or a low-melting fiber, if the hot-air shrinkage rate of the fiber is too high, it is easy to cause uneven thickness due to shrinkage during the production of non-woven fabrics.

Second, why does the non-woven fabric have uneven softness and hardness?

Under the same processing conditions, the causes of uneven softness and hardness of non-woven fabrics are generally similar to those of the above-mentioned uneven thickness. The main reasons may include the following points:

(1) The blending of low-melting fiber and conventional fiber is not uniform. The part with higher content of low melting point is harder, and the part with lower content is softer.
(2) Incomplete melting of low-melting fiber results in softer non-woven fabrics
(3) The high shrinkage rate of the fiber will also cause uneven softness and hardness of the non-woven fabric.

3. Why is static electricity always generated during the production of non-woven fabrics?

(1) The weather is too dry and the humidity is not enough.
(2) When there is no oil on the fiber, there is no antistatic agent on the fiber. Because the moisture regain rate of polyester cotton is 0.3%, the lack of antistatic agent results in static electricity during production.
(3) Polyester cotton because of the special molecular structure of the oil agent, there is almost no water on the oil agent, and it is relatively easy to generate static electricity during production. Usually, the smoothness of the hand feel and the static electricity are in a positive ratio. The smoother the polyester cotton, the more static Big.
(4) In addition to humidification in the production workshop, the method of preventing static electricity can effectively eliminate oil-free cotton during the feeding stage is also an important task.

4. The reason for the hard cotton after the work roll is wrapped

During production, the work roll is entangled with cotton. Most of the reasons are that the low oil content of the fiber causes the friction coefficient between the fiber and the card clothing to be abnormal, and the fiber sinks under the card clothing. When moving, it gradually melts and becomes hard cotton through constant friction and compression between the card clothing and the card clothing. To eliminate entanglement, the method of lowering the work roll can be used to remove the entanglement on the roller.

5. The most appropriate qualitative temperature for processing low-melting fiber

The melting point of the existing low-melting fiber is advertised as 110°C, but this temperature is only the softening temperature of the low-melting fiber. Therefore, the most appropriate processing and setting temperature should be based on the minimum requirement that the lowest temperature part of the non-woven fabric reaches 150℃ x 3 minutes during heating.

6. thinner non-woven fabrics are more prone to short codes

When the non-woven fabric is wound, because the finished product is larger and larger, the linear speed will become larger and larger at the same winding speed. The thinner non-woven fabric is likely to be stretched because of the smaller tension. Short code problems occur due to tension release after rolling.

As for the thicker and medium-sized products, the production resistance is greater, resulting in less stretch, and it is not easy to cause short code problems.