Cellulose fiber and nanofibril characteristics in a continuous sono-assisted process for production of TEMPO-oxidized nanofibrillated cellulose

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Volume Title

A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä

Date

2022-11

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Mcode

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Language

en

Pages

22
9121-9142

Series

Cellulose, Volume 29, issue 17

Abstract

A hardwood dissolving pulp and bleached softwood Kraft pulp were subjected to continuous ultrasonic cavitation assisted TEMPO-mediated oxidation. The effects of such processing on the yield of carboxylic groups, morphological changes of the fibers as well as the effects on the final nanocellulose dispersion were studied. Ultrasonic cavitation in the TEMPO-mediated oxidation phase enhanced the yield of carboxylic groups on both pulps while having a negligible effect on materials losses due to fiber fines formation. The effect of ultrasonic cavitation was purely mechanical and acted as an additional high-shear mixer in the pre-treatment phase. As a result, the morphological changes on the fibers were enhanced, with additional swelling and fiber straightening being observed. Furthermore, the ultrasonic cavitation also influenced the properties of the nanocellulose dispersion obtained from subsequent microfluidization. The sonicated samples exhibited higher optical clarity, higher elasticity in gels while also having somewhat lower viscosities. On nanoscale, ultrasonic cavitation helped the subsequent microfluidization in releasing better individualized nanofibrils as they had smaller diameters than in non-sonicated samples. Sonication also had no effect on the crystallinity properties of the nanocellulose, the observed slight reduction was a result of intense microfluidization that was used to produce the nanocellulose dispersion. Ultrasonic cavitation in the TEMPO-oxidized pre-treatment phase was shown to be a method that can increase the throughput in lab-scale by mechanical activation of pulps and enabling shorter processing times for TEMPO-mediated oxidation. Graphical abstract: [Figure not available: see fulltext.].

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Funding Information: The authors are grateful for Niemi foundation for research grants ID 64930 and ID 64990 for 2020 and 2021, respectively, that financed this work. We also thank The Slovenian Research Agency within the framework of research programs P4-0015 and P4-0121 for making some of the research equipment available to us. The authors would like to acknowledge Senior Scientist Panu Lahtinen from VTT Technical Research Centre of Finland Ltd for helping with the pulp microfluidization trials, and Senior Scientist Jani Seitsonen deserves special thanks for their help with the TEM and WAXS measurements. Funding Information: The authors are grateful for Niemi foundation for research grants ID 64930 and ID 64990 for 2020 and 2021, respectively, that financed this work. We also thank The Slovenian Research Agency within the framework of research programs P4-0015 and P4-0121 for making some of the research equipment available to us. The authors would like to acknowledge Senior Scientist Panu Lahtinen from VTT Technical Research Centre of Finland Ltd for helping with the pulp microfluidization trials, and Senior Scientist Jani Seitsonen deserves special thanks for their help with the TEM and WAXS measurements. Publisher Copyright: © 2022, The Author(s), under exclusive licence to Springer Nature B.V.

Keywords

Cellulose oxidation, Fiber morphology, Nanocellulose, TEMPO oxidation, Ultrasonic cavitation

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Citation

Levanič , J , Svedström , K , Liljeström , V , Šernek , M , Osojnik Črnivec , I G , Poklar Ulrih , N & Haapala , A 2022 , ' Cellulose fiber and nanofibril characteristics in a continuous sono-assisted process for production of TEMPO-oxidized nanofibrillated cellulose ' , Cellulose , vol. 29 , no. 17 , pp. 9121-9142 . https://doi.org/10.1007/s10570-022-04845-7