Characteristics of concentrated cellulose nanofibrils measured by differential scanning calorimetry

• Published in: Cellulose (London) Vol. 30; no. 8; pp. 5019 - 5031
• Main Authors: Liu, Hefang, Tu, Qiyuan, Huang, Luyao, Gao, Wenhua, Zeng, Jinsong, Wang, Bin, Li, Jinpeng, Xu, Jun
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.05.2023; Springer Nature B.V
• Subjects: Bioorganic Chemistry; Bleaching; Cellulose; Ceramics; Chemistry; Chemistry and Materials Science; Composites; Differential scanning calorimetry; Dispersion; Freezing; Glass; Heat measurement; Kraft pulp; Natural Materials; Organic Chemistry; Original Research; Physical Chemistry; Polymer Sciences; Surface stability; Sustainable Development; Differential scanning calorimetry; Cellulose nanofibrils; Concentration; Pore size distribution
• ISSN: 0969-0239; 1572-882X
• DOI: 10.1007/s10570-023-05206-8

The low concentration of prepared cellulose nanofibril (CNF) suspension limits its large-scale application. In this study, bleached hardwood kraft pulp without any pretreatment was prepared into a CNF suspension with a concentration of about 1.0 wt% by a Supermasscolloider. The CNF suspension was dewatered by centrifugation to obtain concentrated CNFs (labeled 1-CNF). The 1-CNF sample was then mixed with water and dispersed by a high-speed homogenizer and dewatered again to obtain re-concentrated CNFs (labeled 2-CNF). The results showed that the suspension stability, water retention value and specific surface area of redispersed CNFs decreased compared to the unconcentrated CNFs. The cavities or pores formed by nanofibrils in the dewatering process were evaluated by the content of freezing bound water (FBW) that was calculated by differential scanning calorimetry with an isothermal step melting procedure. Pores were not observed in the starting unconcentrated CNFs, while the pores with a size of 0–395.8 nm were found in the two concentrated CNF samples (1-CNF and 2-CNF). The FBW content of the CNF samples increased as the solid content of the two concentrated CNFs increased. After re-concentration, the FBW content of 2-CNF decreased compared to that of 1-CNF. In sum, the concentration process of CNF suspension promoted the formation of pores and pores with small size formed first. However, in the re-dispersion and re-concentration process, the formed pores partially collapsed and shrunk. Graphical abstract