University of Oulu

Sirviö, J., Hyypiö, K., Asaadi, S., Junka, K., Liimatainen, H. (2020) High-strength cellulose nanofibers produced via swelling pretreatment based on a choline chloride–imidazole deep eutectic solvent. Green chemistry, 22 (5), 1763-1775.

High-strength cellulose nanofibers produced via swelling pretreatment based on a choline chloride–imidazole deep eutectic solvent

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Author: Sirviö, Juho Antti1; Hyypiö, Kalle1; Asaadi, Shirin2;
Organizations: 1Fibre and Particle Engineering Research Unit, University of Oulu, P.O. Box 4300, 90014 Oulu, Finland
2BillerudKorsnäs AB, Box 703, 169 27 Solna, Stockholm, Sweden
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 4.3 MB)
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Language: English
Published: Royal Society of Chemistry, 2020
Publish Date: 2020-02-24


A deep eutectic solvent (DES) based on choline chloride and imidazole (CCIMI) was investigated for swelling of cellulose fibers prior to mechanical disintegration into cellulose nanofibers (CNFs). The dimensions of the DES treated and washed fibers were investigated after various treatment conditions (time, temperature, and cellulose consistency) using DES based on choline chloride–urea (CCUrea) and pure imidazole as references. Even mild treatment conditions (15 minutes at 60 °C) with CCIMI increased the diameter of the fibers from 18.1 to 18.9 μm, and a maximum diameter of 19.9 μm was obtained after three hours at 100 °C. Overall, CCIMI resulted in a higher degree of swelling compared to both references. In addition, pure imidazole caused a decrease in the degree of polymerization of cellulose, whereas cellulose degradation in CCIMI was negligible. The mechanical disintegration of CCIMI-treated fibers resulted in the production of CNF films with very good mechanical properties—specific tensile strength and work capacity being over 200 kNm kg−1 and 10 kJ kg−1, respectively—whereas CNFs films produced using choline chloride–urea had notably lower values (182 kNM kg−1 and 7 kJ kg−1, respectively). In addition, CNF films exhibited good oxygen barrier properties, even at an elevated relative humidity level (80%). CCIMI could be recycled without any effect on the mechanical properties of CNF films. The results presented here indicate CCIMI is a highly efficient pretreatment media for swelling and further nanofibrillation of cellulose, even at mild treatment conditions.

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Series: Green chemistry
ISSN: 1463-9262
ISSN-E: 1463-9270
ISSN-L: 1463-9262
Issue: 5
Pages: 1763 - 1775
DOI: 10.1039/C9GC04119B
Type of Publication: A1 Journal article – refereed
Field of Science: 221 Nanotechnology
Funding: We acknowledge Mr Sami Saukko, Mr Tommi Kokkonen, and Mr Marcin Selent for their assistance in TEM, TG, and XRD measurements, respectively. Mr Jani Österlund is acknowledged for the film preparation and tensile test, adn BillerudKorsnäs Produktlab Skärblacka for OTR measurements. BillerudKorsnäs AB is gratefully acknowledged for its financial support of this work. The facilities at the Center of Microscopy and Nanotechnology at the University of Oulu were used in this research.
Copyright information: This journal is © The Royal Society of Chemistry 2020. This article is licensed under a Creatice Commons Attribution 3.0 Unported License.