Biodegradable filtration material by foam forming and electrospinning

Research output: Chapter in Book/Report/Conference proceedingConference abstract in proceedingsScientific

Abstract

The recent Covid-19 pandemic has shown how important effective preventive measures that do not disrupt everyday life can be to the society. Respirator protective equipment is an important part of such a toolbox, provided requirements for the extensive usability are ensured by technical developments. We have carried out a cross-disciplinary project where the technical features of a filtration material were developed based on an interview study among young adults. In these interviews, important identified features for masks and respirators were breathability, efficiency, sustainability, and comfort. Currently, most common single-use masks are made of polypropene, and thus littering can be a harmful side effect of their use.
Our material solution combined several technologies by which breathability, efficiency, sustainability, and comfort could be improved simultaneously. The formed filter had a multi-scale structure consisting of a thin permeable substrate and an electrospun nanofiber coating. The quality of the filtration layer is sensitive to the physical properties of the substrate. Thus, the selection of materials and structure forming methods are essential in achieving the set technological targets.
The materials were chosen so that the filter became fully biodegradable. The substrate was foam-formed from regenerated cellulose fibers with low linear mass density. Foam-assisted deposition of the fibres led to a homogeneous and porous structure, enabling fast parallel air flow with insignificant pressure drop. An effective filtration layer was achieved by electrospinning poly(ethylene oxide) (PEO) nanofibers on the smooth substrate surface. The effective filtration of particles at low coat weight was analyzed in terms of the mean segment length of the nanofiber network. For all PEO coat weights, the filtration efficiency increased strongly when the particle size was just below this scale of 0.35 µm. For a particle diameter of 0.6 µm, the filtration efficiency of a single PEO layer varied in the range of 80‒97% depending on the coat weight. Still, air permeability was high because of the strong Knudsen effect imposed by a small mean nanofiber radius. The measured pressure drop had the level of 20‒90 Pa for the airflow velocity of 5.3 cm/s. By altered design, both concepts with high filtration efficiency and moderate pressure drop or high breathability together with significant efficacy could be built up. Using a multilayer structure, a very high filtration efficiency of 99.5% was obtained with only a slightly higher pressure drop than for the structures with a single PEO coating.
The developed features provide significant advantages for the design of next-generation face masks that would meet the required functional properties and user experience. The partial transparency and easy foldability of the filter material provide additional opportunities for the concept design.
Original languageEnglish
Title of host publicationICC2022+1
Subtitle of host publicationBook of Program & Abstracts
PublisherThe Cellulose Society of Japan
Pages67
Publication statusPublished - 27 Sept 2023
MoE publication typeNot Eligible
Event5th International Cellulose Conference, ICC2022+1 - International Conference Center, Hiroshima, Japan
Duration: 26 Sept 202328 Sept 2023
https://icc2022plus1.symposium-hp.jp

Conference

Conference5th International Cellulose Conference, ICC2022+1
Country/TerritoryJapan
CityHiroshima
Period26/09/2328/09/23
Internet address

Keywords

  • filtration
  • foam forming
  • electrospinning
  • cellulose
  • poly(ethylene oxide) (PEO)
  • usability

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