The Verdex nanofiber spinning process allows for the introduction of functional particulates to be suspended in the fiber network. A wide range of particulate diameters and loadings can be accommodated thanks to dual methods of retention, Entanglement and Surface Bonding.

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For particles greater than 10x the mean fiber diameter, approximately 2 microns and larger, the main mechanism of particle retention is entanglement. When a particle is introduced to the fibers as they are being formed, turbulent interactions cause the fibers to wrap around it and bond to the existing fiber network. This creates a permeable "net" in which the particle is mechanically captured, but still has the majority of its surface area exposed to the gas stream, allowing it to maintain a high level of functional efficacy.

 

For particulates less than or equal to the mean fiber diameter, approximately 0.5 microns and smaller, the main mechanism of particle retention is surface bonding. When a particle is introduced to the fibers as they are being formed, it comes into contact with a still molten strand of polymer and bonds to the surface. As the fiber cools, the particle become mechanically locked into the surface, while still having a majority of its surface area exposed. This again allows for a high degree of gas/particulate interaction.

 

Particulates between 0.5 and 2 microns are retained by a combination of entanglement and surface bonding working in tandem. These two methods allow for high loadings, exceeding 500% by weight.

 

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Incumbent products utilize either adhesives or mechanical screening to achieve particle retention, which have significant drawbacks when compared to the Verdex process. Adessives can drastically negatively impact the permeability of the fiber structure, reduce the effective surface area of the functional particles due to occlusion, or fail over time due to exposure to moisture or other environmental factors. Mechanical screening on the other hand requires the use of much larger particulates in order to be adequately retained. This increase in particle diameter reduces the surface area per unit volume, which drastically reduces efficiency of gas interaction. In order to offset this effect a larger amount of particulates must be used, increasing material cost.

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