“…Although the textile industry mostly used it for fabric production, needle punching was also successfully applied for the production of PE, PP, acrylic, as well as recycled PE and cotton-based polymeric air filters. [116][117][118] Aramid nonwovens, manufactured by carding and bonding, were recently impregnated in phosphoric acid to generate a large number of nanofibrils on the fiber surface and subsequently impregnated with CuO-CeO 2 catalysts, allowing for easily scalable production. [119] Other elaborated methods include freeze drying of nanofiber suspensions, e.g., from MOF-functionalized cellulose.…”
Particulate and gaseous air pollutants pose a threat to human health and contribute to climate change. By today, air filters, stationary and portable, are markedly improved and can often provide innocuous air pollution levels. After introducing the classification and standards on air filters, the influence of the processing route and its parameters on the resulting air filter properties and consequently its performance are discussed. Numerous tools are presented to adjust structural properties such as fiber or pore diameter, specific surface area, surface charge, hydrophilicity, or photocatalytic activity to achieve the desired performance in terms of high filtration efficiencies, sufficient mechanical stability, regeneration eligibility, antimicrobial and optical properties. In particular, inorganic and composite materials as well as nonfibrous structures are covered, which are currently holding an outsider position in an air filter community dominated by polymeric materials and fibrous structures.
“…Although the textile industry mostly used it for fabric production, needle punching was also successfully applied for the production of PE, PP, acrylic, as well as recycled PE and cotton-based polymeric air filters. [116][117][118] Aramid nonwovens, manufactured by carding and bonding, were recently impregnated in phosphoric acid to generate a large number of nanofibrils on the fiber surface and subsequently impregnated with CuO-CeO 2 catalysts, allowing for easily scalable production. [119] Other elaborated methods include freeze drying of nanofiber suspensions, e.g., from MOF-functionalized cellulose.…”
Particulate and gaseous air pollutants pose a threat to human health and contribute to climate change. By today, air filters, stationary and portable, are markedly improved and can often provide innocuous air pollution levels. After introducing the classification and standards on air filters, the influence of the processing route and its parameters on the resulting air filter properties and consequently its performance are discussed. Numerous tools are presented to adjust structural properties such as fiber or pore diameter, specific surface area, surface charge, hydrophilicity, or photocatalytic activity to achieve the desired performance in terms of high filtration efficiencies, sufficient mechanical stability, regeneration eligibility, antimicrobial and optical properties. In particular, inorganic and composite materials as well as nonfibrous structures are covered, which are currently holding an outsider position in an air filter community dominated by polymeric materials and fibrous structures.
“…Both the fiber mass and air permeability are dark in the left region of the filter, particularly in the center of the upper side, and the correlation between them is high. Thus, air permeability was low where the fiber mass was high, and conversely, the air permeability increased if the fiber mass was low 16, 17. On the other hand, the thickness distribution did not show large spatial changes.…”
The accurate determination of physical properties of filtration media is essential for predicting their performance for bag filtration use. The spatial distributions of fiber mass, air permeability, and thickness of three commercially available filtration media were evaluated and compared with the manufacturer's indicated values. The fiber mass and air permeability were distributed over a wide range, resulting in a large deviation from the indicated values. The filter efficiencies were measured for ten randomly sampled pieces from each filter, and the filter efficiency of the whole filtration media and particle emission rate were estimated. Even for filters with a fiber mass and air permeability close to the indicated values, their filter performances differed by approximately 15 %.
“…10 However, the influence of air permeability in fibrous material is extraordinary intricacy, which contains relatively high volume of air and very complex pore structure due to the random arrangement of fibers in the non-woven fabric. 29 Figure 7(a) shows the air permeability of GFFs with different dispersing times and speeds. Air permeability did not change too much with increasing dispersing times and speeds, except dispersing speed was 3000–5000 r/min for 8–10 min (red area).Figure 7.Physical properties: (a) Air permeability of GFF, (b) Thickness of GFF.…”
Glass fiber felt (GFF) as a fibrous and porous material has caught much attention because its light mass, low cost and excellent acoustic properties. In this paper, GFF was prepared via the papermaking technique to explore the correlation between glass fiber suspension characteristics and physical properties (uniformity, air permeability and sound insulation) of GFF. The consequence presented that increasing the dispersing times and speeds could decrease aspect ratio and flocculation of fibers, which was useful to improve viscosity and fiber hanging property of glass fiber suspension, and uniformity of GFF. However, there was no visible impact on the air permeability of GFF. The results also indicated that increasing the dispersing times could decrease sound transmission loss (STL), however which could be enhanced by changing the dispersing speeds. The optimal dispersing speed was 3000 r/min and STL could be reached 15.78 dB at 6300 Hz. Generally, GFF could be used as acoustic material for building and transportation.
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