Textiles for filtration

According to the European Environment Agency (EEA), fine particulate matter (particles smaller than 2.5 µm in diameter) is responsible for more than 180,000 deaths per year across the 27 countries of the European Union . Emissions of these particles result from various human activities: exhaust from internal-combustion vehicles, combustion-based heating systems (wood, fuel oil, etc.), and industrial activities. The air we breathe also contains particles emitted by the wear and tear of consumer goods, sanding operations, or pollen, all of which can have health consequences. Filtration using porous media is commonly used to protect people from exposure to these airborne particles. Processes utilizing this technique are employed in both collective and individual protection solutions and span numerous sectors: industrial, medical, service, and residential. Applications are varied and can range from filtering combustion fumes to filtering ambient air, using face masks or various filters installed on machinery.

Before the 1960s, structured textiles—that is, woven or knitted fabrics—were used to manufacture personal protective masks, even in the medical field. The raw materials used were natural, primarily cotton. Since the 1960s, with the widespread adoption and massive use of petroleum-based polymers, masks have primarily been made of randomly entangled synthetic filaments, also known as “nonwovens.” These offer very high filtration efficiency. They are faster to produce than structured textiles and are therefore much less expensive. They are so inexpensive that they can be used only once, which eliminates the problem of cleaning. These undeniable advantages have established them as the sole solution for filtration devices, almost completely halting research into the performance of structured textiles in this field. However, the global SARS-CoV-2 pandemic has highlighted the limitations of the monopoly of nonwoven filtration, particularly as used in surgical masks. These single-use masks are rarely recycled and are mainly incinerated, resulting in a significant environmental impact. Furthermore, nearly every country in the world faced a shortage of disposable or surgical masks in 2020. One solution was the use of washable cloth or knitted masks, often crafted using traditional methods. This has reignited research into the filtration performance of structured textiles and the potential relationships...