(a) Schematic illustration of a highly selective permeable fiber mat blocking the penetration of toxic vapor, liquid and aerosol while maintaining water vapor transmission. (b) PIM-1 fiber web. (c) PIM/PAN fiber web with integrated PAN layers in PIM-1 matrix. (d) PIM/PAN/MOF composite fiber web with MOF particles incorporated in between PIM/PAN layers.
(a) Schematic illustration of a highly selective permeable fiber mat blocking the penetration of toxic vapor, liquid and aerosol while maintaining water vapor transmission. (b) PIM-1 fiber web. (c) PIM/PAN fiber web with integrated PAN layers in PIM-1 matrix. (d) PIM/PAN/MOF composite fiber web with MOF particles incorporated in between PIM/PAN layers.

Medics, armed forces, firefighters, and law enforcement personnel responding to emergencies need protective clothing, which must simultaneously keep out harmful substances while allowing water vapor to pass through for wearers’ comfort. Current state-of-the-art garments use multi-layered fabrics with activated carbon (AC) to absorb harmful agents and other materials for filtration. But this combination makes for hot, bulky garments that become contaminated with the absorbed toxic chemicals.

Now researchers from North Carolina State University and the US Army Combat Capabilities Development Command Solider Center in Natick have designed a highly adsorbing, breathable, mechanically robust fabric that not only filters out harmful aerosol matter but can catalytically degrade chemical warfare agents [Wang et al., Materials Today Advances 8 (2020) 100085, https://doi.org/10.1016/j.mtadv.2020.100085].

“We [wanted] to design a material that can provide protection and comfort simultaneously,” explain researchers Saad A. Khan, Greg N. Parsons, and Siyao Wang. “[Our] lightweight, multifunctional chemical protective fabric [combines] vapor and aerosol protection in one sorbent material with filtering and detoxification capabilities.”

The novel fabric is based on an electrospun fibrous mat of a polymer of intrinsic porosity (PIM), which possesses high surface area and interconnected pores that are able to adsorb toxic vapors. Simultaneously, gaps between the fibers trap micron-sized pollutants such as PM2.5 and PM10 (2.5- and 10-micron particles, respectively). The hierarchical nature of the porous structure, with pores ranging from the micro- (<2 nm) to the macro (>50 nm) scale, meanwhile, provides pathways for air and water vapor molecules to move through. To add to the mechanical strength and filtration capabilities, polyacrylonitrile (PAN) nanofibers are layered onto the fibrous mat. Finally, tiny Zr-containing ‘beads’ of a metal-organic framework (MOF) (UiO-66-NH2) are incorporated between the layers to degrade chemical warfare agents catalytically.

“The combination of sorption and particle filtration into a single fabric greatly reduces the thermal burden for the wearers,” point out the researchers.

As well as remarkable adsorption, filtration, and degradation capabilities, the fibrous mats also retain a high water vapor transmission rate and are much stronger than simple PIM fibers.

“Our next step is to evaluate the toxic gas adsorption capacity of PIM under different levels of humidity,” say the researchers.

To create actual garments, the composite fibrous mat would have to be laminated with the cover fabric on top for durability and liquid repellency and a comfort liner underneath.

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