Electrostatic charging is a technique used to enhance the filtration efficiency of meltblown nonwoven fabric. By imparting an electrostatic charge to the fibers, the fabric can effectively capture and retain even smaller particles, including ultrafine particles and aerosols. The electrostatically charged meltblown fabric acts as a magnet, attracting and trapping particles that would otherwise pass through a non-charged fabric.

Here’s how electrostatic charging improves the filtration efficiency of meltblown fabric:

Enhanced Particle Capture: The electrostatic charge on the fibers creates a strong attraction force between the fabric and particles. As airborne particles pass through the fabric, they are drawn towards the charged fibers and adhere to the fabric’s surface or get trapped within the interstices of the fabric. This mechanism significantly increases the fabric’s ability to capture and retain particles, even those smaller than the gaps between the fibers.

Reduction of Particulate Penetration: The charged fibers repel particles with the same charge, preventing them from passing through the fabric. This electrostatic repulsion helps to reduce particulate penetration and enhances the fabric’s barrier properties.

Depth Filtration Effect: The electrostatically charged meltblown fabric not only captures particles on the fabric’s surface but also allows for depth filtration. The charged fibers create an electric field that can attract particles into the fabric’s structure, increasing the overall filtration efficiency.

It’s worth noting that the electrostatic charge applied to meltblown fabric may gradually diminish over time due to factors like humidity, mechanical stress, or washing. Therefore, maintaining the electrostatic charge is crucial for sustaining the enhanced filtration efficiency. Certain treatments or coatings can be applied to the fabric to help preserve or restore the electrostatic charge, ensuring its long-term effectiveness.

Electrostatically charged meltblown nonwoven fabric has been widely used in respiratory protection, such as N95 respirators, as well as in other high-efficiency filtration applications where capturing small particles is essential.

What are some common treatments or coatings used to maintain the electrostatic charge on meltblown fabric?

To maintain or enhance the electrostatic charge on meltblown fabric and prolong its filtration efficiency, several treatments or coatings can be applied. Here are a few common methods:

Corona Discharge: Corona discharge treatment is a widely used technique to create and maintain the electrostatic charge on meltblown fabric. In this process, the fabric is passed through a high-voltage corona discharge field. The electric discharge charges the fibers, creating an electrostatic field that enhances particle capture. meltblown nonwoven fabric This treatment can be performed during or after the meltblown process.

Tribocharging: Tribocharging involves introducing friction between the meltblown fabric and another material with different electrical properties. The friction generates an electrostatic charge on the fabric. The additional material can be in the form of powders, films, or coatings, such as carbon-based materials or metallic powders. The tribocharging effect helps to maintain the fabric’s electrostatic properties.

Electrostatic Spray Coating: Electrostatic spray coating involves applying a charged liquid coating onto the meltblown fabric. The charged particles in the liquid are attracted to the oppositely charged fibers, resulting in a coating that enhances the fabric’s electrostatic properties. This method can be used to restore or enhance the electrostatic charge on the fabric’s surface.

Hydrocharging: Hydrocharging is a technique that utilizes moisture or humidity to maintain the electrostatic charge on meltblown fabric. The presence of moisture can help retain the electrostatic properties of the fabric, making it more effective in capturing particles. However, it’s important to note that excessive moisture can negatively impact the fabric’s performance and should be controlled within optimal ranges.

These treatments or coatings can be applied individually or in combination to achieve the desired level of electrostatic charge and filtration efficiency for specific applications. The selection of the appropriate method depends on factors such as the desired level of charge, fabric composition, processing capabilities, and environmental conditions.

It’s worth mentioning that the effectiveness of these treatments may vary, and the fabric’s electrostatic charge may diminish over time or with repeated use. Regular testing and evaluation of the fabric’s filtration performance are necessary to ensure its continued effectiveness.