Polypropylene tourmaline powder

Fine tourmaline powder can be used as electret material. Electret is an electrolyte material with the function of long-term charge storage. The electret methods mainly include electrospinning, corona charging, friction electrification, thermal polarization, low-energy electron beam bombardment, etc. Tourmaline electret material uses corona charging method to make the fiber take a certain amount of charge and endow it with electrostatic filtering function.

There are two ways to improve the charge storage capacity of Electret Materials:

1. By improving the crystallinity and mechanical deformation of the material, the structure of the material is changed to form slender hole channels to prevent charge drift.

2. A charge trap is generated by introducing an additive with charge storage performance to capture charge.

The polarization of electrets made of non-polar materials is mainly caused by space charge. There are two types of space charges: one is called the same sign charge and the other is called the different sign charge. The former is attributed to the conductivity between the dielectric and the electrode or the electric breakdown near the dielectric surface under the action of strong electric field, which causes the electrode to inject charge into the dielectric; In this way, the polarity of the injected space charge is the same as that of the adjacent electrode. The polarity of different sign charges is opposite to that of adjacent electrodes, which is mainly due to the separation and capture of charges in the dielectric. The electret charge formed by dipole orientation in polar dielectric is another type of different sign charge.

The addition of tourmaline particles can effectively improve the electret efficiency, increase the filtration efficiency, reduce the filtration resistance, increase the charge density on the fiber surface, and enhance the charge storage capacity of the fiber mesh. The comprehensive effect of adding 6% tourmaline electret is better. Too many electret materials will increase the carrier movement and neutralization phenomenon.

The process of melt blown electrostatic electret is to add tourmaline, silica, zirconium phosphate and other inorganic materials into PP polypropylene polymer in advance, and then charge the melt blown material by one or more groups of corona discharge with the voltage of electrostatic generator needle electrode of 5-10kv before cloth rolling. When high voltage is applied, the air below the needle tip will produce corona ionization and partial breakdown discharge, The carriers are deposited on the surface of the melt blown cloth through the action of electric field. Some carriers will go deep into the surface and be captured by the trap of electret masterbatch, so that the melt blown cloth can become electret filter material.

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