I'm doing a research about nanocellulose, I hope I can get porous film from nanocellulose by simple drying method, but it can't. The nanocellulose solution will form continuous film after drying because strong hydrogen bonding between every cellulose fiber. Freeze drying makes it possible, but this process is not efficient in large scale. Is there anyone can give me some suggestion? Thanks.
At the moment drying process are being study, one of them is freeze drying, but there are another:
- Solvents exchanges
- Spray drying
Any film/paper of nanocellulose you make is still porous! However, depending on how you do prepare your film/paper (filtration and drying under pressure or simple drying) the porosity will vary between 50-30% (which incidentally also affects the mechanical properties of your paper). The film density you can simply measure (aerial weight/film thickness) and porosity = 1- film density/cellulose density (usually around 1500 kg/m3). The pore dimensions are governed by the fibril diameter and about the same size.
What do you actually want to achieve? Redisperse dried NFC? Or make porous films?
Hope it helps?
Thanks Alexander for your response. I want to make porous nanocellulose film for air filtration purpose. The pore diameter is about 500 nm- 1 micron. Do you have any suggestion? Thanks
You may consider "regenerated cellulose in NaOH / thiourea (urea) aqueus solution". This way you can achive cellulose nanoporous film.
Dear Ricky, this should be possible and even more so since in this case you don't really need very fine NFC. We made nano paper membranes down to the tight UF range with pore sizes around 15 nm by paper-making. The key for you should be to tailor the fibril diameter (as mentioned before this will govern the pore diameter) and the hornification (i.e. irreversible H-bonding between the fibrils) between the fibrils so you produce the porosity desired. If it helps do check out our papers on that subject matter.
Regarding Aleksandr's response, you would made regenerated cellulose films but they have virtually no pores and might be good only for membrane applications.
Hope it helps?
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