Medical masks proved effective in protecting against the virus during the Covid-19 pandemic. However, conventional masks are poorly biodegradable. For this reason, the presented paper produced environmentally friendly chitosan/silver/plant fiber membranes for masks, which also exhibited antibacterial and thermal properties.
ENVIRONMENTALLY FRIENDLY CHITOSAN/SILVER/PLANT FIBER MASKS WITH THERMAL ADJUSTMENT AND SELF-STERILISATION
Zou, Q., Gai, Y., Cai, Y. et al. Eco-friendly chitosan@silver/plant fiber membranes for masks with thermal comfortability and self-sterilization. Cellulose (2022). https://doi.org/10.1007/s10570-022-04582-x
During the Covid-19 pandemic, the wearing of medical masks proved effective in protecting the public from the virus. Worldwide, 129 billion masks are consumed per month. Because the filter layers of conventional masks are made of polypropylene (PP), they take about 10 years to degrade in landfills and thus pose an environmental burden. They also have poor thermal conductivity, which causes warm and moist air to collect under the mask, restricting the user's ability to breathe. It also increases the risk of bacterial infections.
For this reason, chitosan (CS) is of interest as a raw material for filter membranes. In addition to its biodegradability, it also has antibacterial properties. These can be further enhanced in combination with silver nanoparticles (AgNPs). Silver also has excellent thermal and electrical conductivity. In the presented study, CS fibers were used as carriers for in situ reduced AgNPs to produce CS-Ag core-shell fibers. In combination with plant fibers (cellulose), this was to produce a continuous network for filter membranes. Besides the fabrication and characterization of the fibers, the thermal and antibacterial properties were also investigated.
- Evidence via SEM and EDS that AgNPs are uniformly and closely distributed on the surface of chitosan fibers → formation of a core-shell structure
- AgNPs increase conductivity of CS fibers
- Successful combination with plant fibers via suction filtration
- Evidence of significantly improved air permeability and higher PM2.5 levels compared to conventional PP filters
- Addition of C13H13F17O3Si converts the hydrophilic material into a hydrophobic one → formation of self-cleaning and anti-fouling properties
- CS-AgNPS plant fiber membranes exhibited 4.45 times higher thermal conductivity than conventional PP masks → improved cooling properties when worn
- Evidence of high conductivity and low electrical resistance enable heating of masks in cold regions and killing of viruses and bacteria when heated above 80 °C
- Antibacterial rates of the filter material of over 99% against E. coli and S. aureus by CS and AgNPs
Summary: In the presented study, an environmentally friendly and multifunctional filter material for masks was successfully fabricated from CS, AgNPs and plant fibers. In this study, the CS-AgNP core shell structure exhibited good thermal and electrical conductivity, which can be utilized for a cooling effect when hot and a heating effect when cold. In addition, excellent antibacterial properties of the material were observed. Overall, CS-AgNP plant fibers thus have great potential as a filter material for medical masks.