How to choose the right electrostatic electret generator

As the US FDA/CDC canceled nearly 80% of the mask whitelist companies in China, it encountered the Canadian government requiring dozens of Chinese mask factories to recall unqualified products on their own. Since May, many people in the mask chain industry have discussed that this industry has entered the bottom. We believe that as long as the new crown special drugs or vaccines do not appear, global masks will still be just needed, but the market will gradually phase out unqualified products, and the mask chain will gradually become rational. The melt-blown cloth at the core of the mask has only real long-term filtering effect only after reaching the standard and being even can we survive.

Electrostatic electret is the best way to improve the filtration efficiency of the melt-blown cloth after selecting the best raw material formula, using the best equipment and process, but it should be emphasized that the Electrostatic electret should not be used as a kind of “wanjin oil”when improving the filtration efficiency of the melt-blown cloth , the filterability of the cloth made by that type of artillery machine is only 10-20% after adding the masterbatch. The first thing to consider is the formula and process of changing raw materials, and then the static electret. The following is a professional response from Shanghai LISUN to the most frequently encountered problems in the meltblown fabric industry:

1. Is it better to choose a bigger voltage or Frequency of the electrostatic electret generator?
   Reply: The voltage and power are not as large as possible. We need to deposit positive/negative charges on the molecular layer of the meltblown cloth. If the voltage and power are too large, it is easy to destroy the molecular layer of the meltblown cloth so that static electricity can only be added. On the surface of the cloth, static electricity will usually run out after 2-3 days. Experiments have shown that the electrostatic electret equipment usually used on melt-blown cloth has a voltage between 20-60KV, and the appropriate power is selected according to the width of the cloth.

2. Is it correct to produce a visible arc (commonly known as spark) when electricity electret is working?
   Re: The sparks which can see by our eyes will penetrate the meltblown cloth. The following test result is a typical report caused by spark breakdown. The filterability of 5.0um is far below 3.0um.

3. Is it possible to feel a strong current or feel hand numb when electricity electrets generator is working?
   Reply: As reply in question 1, a cloth that feels very strong Static electricity does not mean a cloth with good filterability, because it may not be inside. On the contrary, according to the actual experiment, the static electricity of the melt-blown layer of the 3M KN95  from USA and the KF94 finished masks from Korea does not exceed 2KV, and there will be no static sensation when you touch it. Filterability testing which is reached the PFE is the gold standard.

4. Is the cloth can stick to the wall or bounce back after used the electrostatic electret generator means filtering cloth?
   Reply: Being able to stick to the wall or rebounding back does not mean that the filtering effect is good, the reason may still be the static electricity on the surface. Of course, if the cloth that has just finished static electricity cannot be attached to the wall at all or cannot rebound at all, there may be problems. However, to determine the quality of the cloth, only the data passed the PFE filterability test.

5. Is it better to add positive electricity to cloth or negative electricity?
   Re: We tested nearly 80 samples and found that most of the melt-blown fabrics on the market with masterbatch but no static electricity showed polarity as shown in the figure below. And through these 80 samples, a small rule was found: when the materials made by Sinopec showed more negative electrodes, the non-Sinopec materials such as Secco, Jinfa and other materials showed more positive electrodes. If you already have a stable raw material formula and process, based on the data from Shanghai Lisun’s 10-day experiment (see table E2 in question 8 is better than E1 and E8), we recommend adding the same to the original polarity Static electricity will be easier to power up and maintain electricity (please note that this recommendation may not be rigorous due to limited experimental data). If you cannot determine the polarity of your meltblown cloth, you can send the cloth to Shanghai Lishan and we will test it for you for free .

6. Is it better to use a molybdenum wire electrostatic rod or a needle tip electrostatic rod electret?
   Re: It seems that an electrostatic rod of molybdenum wire can achieve constant current, but in fact a straight line does not point to the melt-blown cloth. Polarized ions will escape around the molybdenum wire due to scattering and cannot be well on the surface of the melt-blown cloth. Corona occurs, and most of them end up on the surface of the cloth. The needle-type electrostatic rod can polarize the ions and accelerate the negative (positive) along the direction of the needle tip to produce a corona effect directly on the meltblown cloth and reside in the molecular layer. Of course, the electrode is prone to generate uneven static electricity Field, this puts extremely high requirements on the needle-type electrostatic rod. A circuit is designed in the needle-type electrostatic rod. The constant voltage output of the electrostatic host and the circuit of the electrostatic rod through the electrostatic rod ensure that each needle can output a constant current at the same time. The corresponding voltage and height values are adjusted at the factory to ensure the best corona effect.

7. Is the static value of the cloth that has just finished static electricity tested with an electrostatic tester as large as possible?
   Reply: In principle, it will be better if it is larger, but if the premise is to be stationed instead of using a high-voltage high-power all on the surface, the final effect is still recommended to use PFE filter testing equipment to judge.

8. The melt-blown cloth which is produce on that day and test more than 95% , can I sell it for a good price?
   Reply: As the market demand for the quality of masks is getting higher and higher, and meltblown cloth is the “heart” of the masks. So the  mask manufacturers will require the meltblown fabric to be transported to stand for 7 days and then check its filterability, then it is required that the meltblown fabric can be maintained at more than 95% after 5-7 days, while also ensuring that this batch of cloth is filtered The sex should be even, not less than 90%. According to the experimental data jointly conducted by Shanghai Lisun and a meltblown fabric factory in Guangdong, many electrostatic electret devices on the market cannot be well-electret to the molecular layer, resulting in 98% of the cloth in 3 days, but after 5-7 days It becomes 90% cloth (see E8), and the use of Shanghai Lisun high-frequency version of the electrostatic electret equipment, especially the negative E2 shows a good retention of filterability, almost no change in 10 days.

9.  Does the bigger the static electret electrified chassis I bought, the effective is better?
Reply: The static electret host must ensure that the output voltage is stable and the ripple is small. Obviously, it is the best way to convert high-frequency output DC through commercial power. The type of large chassis is usually realized by doubling the power frequency transformer with low cost and large volume in combination with ballast. It does not change the electrical performance at all and is directly affected by the national grid. For example, the maximum 10% voltage drop and unpredictable frequency Ripple interference, which will inevitably cause the problem of uneven electrostatic field.

10. Our cloth is produced by the with of 1200 mould, why is the filterability of the cloth made at the same time not uniform? It has max. 10% difference.
    Re: Selecting a high-frequency electrostatic electret generator plus a pin-type electrostatic rod that can output a constant current is the best choice, because it is necessary to ensure that each needle produces a constant current and a stable current. Only high-frequency design electrostatic electret generator thatcan meet the constant voltage (see the figure below), and the pin electrostatic rod processed by the circuit can meet the constant current, and the cloth produced in this way can be uniformly electret.

11. How should I install the electrostatic electret generator I bought?
    Reply: The height of the electrostatic rod and cloth will affect the voltage and current, and also need to be well grounded. A wiring diagram is recommended as follows:

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