How to choose the right electrostatic electret generator for meltblown cloth? Do you really need 120KV?

Mr. Wang was the earliest batch of melt-blown fabric bosses in Yangzhong. Due to the strict management of the government and the strict requirements on the quality of melt-blown fabrics by mask manufacturers, Mr. Wang is talking to  engineer Liu, an expert on melt-blown fabrics  who Secretary Zhang has invited today, to talk about how to transform his several production lines.

Secretary Zhang: Boss, this is engineer Liu , a melt-blown cloth expert in Shanghai LISUN. He can help us improve the quality of melt-blown cloth.

Engineer Liu : Hello, Mr. Wang! Let me introduce myself first. I graduated from Donghua University with a master’s degree in textiles. At that time, I assisted the instructor in the drafting of GB/T32610-2016 “Technical Specifications for Daily Protective Masks”. But now in charge of the “meltblown electrostatic electret generator” “Project in LISUN, we have some experience on how to improve the quality of meltblown cloth.
Boss Wang: Very welcome, why do we add static electret to the meltblown cloth?

Engineer Liu: Add electrostatic electret to the meltblown cloth containing electret masterbatch raw materials, and capture bacteria and particles through the double action of mechanical barrier and electrostatic adsorption, which can significantly improve its filterability. Due to the continuous improvement of the domestic epidemic situation, the blue ocean market for a period of time in the future mask market must be overseas. Since the customs stipulates that only whitelisted mask companies can export, then meltblown fabric manufacturers must improve their product quality.

Boss Wang: Will the melt-blown cloth reach the N95 standard after the static electret is added?

Engineer Liu: It can be said that the N95 standard must not be reached without the addition of static electrets, but it cannot be guaranteed to be 100%, because the production of melt-blown cloth is a complicated process, and the quality of the substrate of the melt-blown cloth is caused by Determined by materials and production process.

Secretary Zhang: There are many specifications of electrostatic electret generators on the market, usually 30KV, 50KV and 120KV, what kind of product should we choose?

Engineer Liu:  First of all, we must understand the purpose of adding high voltage when doing electrostatic electret: 1. Let the charge escape, this voltage is called the escape voltage, usually 2KV can achieve the goal. 2. It is necessary to accelerate the escaped charge into the electrified masterbatch. This voltage is called the accelerating voltage. Normally, it is better if there is no arcing spark. The test shows that the best between 15-50KV, the discharge distance 4- 8cm. On the contrary, if the applied voltage is too high, such as more than 50KV, it is easy to destroy the molecular structure of polypropylene. If it is too close, it will produce an arc spark to break through the meltblown cloth. If it is too far, the charges will be wasted due to scattering and will waste a lot of charge. It cannot be settled in the masterbatch and thus the cloth’s electrostatic field is insufficient. Using the Japanese SIMCO FMX-004 static test instrument to test the static electricity of the melt-blown cloth of the 3M N95 mask is about 2-3 kV, which means that the current static electricity storage of the best brand masks to the user is only several thousand volts. Of course, the melt-blown fabric manufacturer chooses an electrostatic output voltage that minimizes damage to the melt-blown fabric and can maximize its electrostatic field to a reasonable electrostatic output voltage, but must not generate arc sparks to avoid breakdown of the melt-blown fabric. Shanghai LISUN test shows that the best is between 5-50KV, and the discharge distance is 4-8cm.

Boss Wang: To be honesty, we bought a 120KV electrostatic electret in Guangdong before. It seems to have no effect. Can you help us find out why? Secretary Zhang will get it later.

Engineer Liu: I think Secretary Zhang a girl  who took with both hands. The 120KV electrostatic pagoda tested the actual output voltage of only 23.5KV. Obviously, there is voltage stealing. In addition, the power consumption of the power frequency design is also relatively large, which results in discharge output current. It is very small, and you can hardly feel the “electrostatic ion wind” when you put it 8cm away from the electrostatic rod. Most of the static electricity is only on the surface of the cloth, and there will be electricity running after 2-3 days. Normally, an electrostatic electret generator with 120KV full power should have 50*40*80cm and about 90kg. It is usually used for electrostatic treatment of metal products instead of melt-blown cloth. The price will not be lower than 3-5 million RMB. In fact When it is used on the meltblown cloth, it is only adjusted between 5-50KV, which will cause excessive specification waste.

Secretary Zhang: Boss, we were deceived. No wonder our mask factory did not pass the test after the cloth was produced. Then engineer Liu , what kind of electrostatic electret generator should we choose? Engineer Liu: Our newly developed high-frequency version of “Electrostatic Electret Generator for Meltblown Fabrics”, newly developed by Shanghai LISUN, has its own electrostatic field detection function. So that customers can know how much voltage is added during debugging. The high-frequency design solves the traditional in the case of unstable frequency output, use the electrostatic pagoda to calibrate the electrostatic output before leaving the factory and use the oscilloscope to detect the high-frequency switch. Each set of products includes a “calibration certificate”, which can make the electrostatic output voltage accuracy reach +/-0.1% (Traditional the power frequency design is +/-10%), so as to ensure that every inch of meltblown cloth is evenly powered, and the product is guaranteed for one year.

Boss Wang: From your explain, I know you are professional manufacture of electrostatic equipment. The electrostatic pagoda and oscilloscope are calibrated and a calibration certificate is randomly provide. It also includes an electrostatic field detection function. Let us laymen know to debug electrostatic electret generator.

Tags：ESD-RPB