{"title":"Rheo-impedance behavior of cellulose nanofibers produced by mechanical processing","authors":"Yoshifumi Yamagata, Yuichi Takasaki, Keisuke Miyamoto","doi":"10.1007/s10570-024-06242-8","DOIUrl":null,"url":null,"abstract":"<div><p>CNFs are one of the renewable and the sustainable resources with low environmental impact and have various characteristics such as increased strength and weight reduction when added to resins. Since CNFs are one of the new materials that can fulfill the goals of the Sustainable Development Goals (hereafter abbreviated as SDGs), many researchers have been studying the nano-fibrillation of wood fibers. From the viewpoint of SDGs, it is necessary to avoid using a large amount of chemical agents and consuming a large amount of energy for the production of CNFs. To realize these requirements, it is important to find a way to industrially utilize CNFs containing insufficiently nanosized fibers, and for these purposes, it is essential to evaluate the physical properties of these CNFs from multiple perspectives. Cellulose fibers are intrinsically insulating materials, but how their electrochemical properties are changed by nano-fibrillization has been little studied. Therefore, we decided to clarify the relationship between the size of CNFs and the electrochemical impedance properties of the CNF suspensions containing un-fibrillated fibers, which were prepared by a wet refinement system. The fiber diameter remained constant as the number of mechanical treatments (hereafter referred to as the “number of collisions”) increased. On the other hand, the cumulative medium volume diameter, D<sub>50</sub>, defined as the apparent fiber length (hereafter referred to as the “fiber length”, in microns), significantly decreases with the increasing number of collisions. The rheo-impedance |Z| of the CNF suspension remained nearly constant in the intermediate frequency range of 10<sup>3</sup>–10<sup>6</sup> Hz, even if the internal structure of the system was deformed by the increasing shear rate. This means that the electrochemical properties of the CNFs are independent of the changes in the macroscopic aggregation structure. Furthermore, the internal resistance <i>R</i><sub>1</sub> calculated from the impedance |Z| characteristics (Nyquist plot) became decreased with the increasing number of collisions, indicating a proportional relationship between the resistance <i>R</i><sub>1</sub> and the CNF fiber length, D<sub>50</sub>. This suggests that <i>R</i><sub>1</sub> related to the resistance caused by the electrolyte in the suspensions or the protons dissociated by the hydration of the hydroxyl groups of the cellulose molecule as they move across the gaps between the microfibrils. Based on these results, it appears that the electrochemical properties of the CNF suspensions are independent of the changes in the macroscopic aggregation structure and simply depend on the fiber length, in other words, the electrochemical properties are a useful method for indirectly evaluating the fiber length of the CNFs.</p></div>","PeriodicalId":511,"journal":{"name":"Cellulose","volume":"31 18","pages":"10771 - 10784"},"PeriodicalIF":4.9000,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10570-024-06242-8.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Cellulose","FirstCategoryId":"88","ListUrlMain":"https://link.springer.com/article/10.1007/s10570-024-06242-8","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, PAPER & WOOD","Score":null,"Total":0}
引用次数: 0
Abstract
CNFs are one of the renewable and the sustainable resources with low environmental impact and have various characteristics such as increased strength and weight reduction when added to resins. Since CNFs are one of the new materials that can fulfill the goals of the Sustainable Development Goals (hereafter abbreviated as SDGs), many researchers have been studying the nano-fibrillation of wood fibers. From the viewpoint of SDGs, it is necessary to avoid using a large amount of chemical agents and consuming a large amount of energy for the production of CNFs. To realize these requirements, it is important to find a way to industrially utilize CNFs containing insufficiently nanosized fibers, and for these purposes, it is essential to evaluate the physical properties of these CNFs from multiple perspectives. Cellulose fibers are intrinsically insulating materials, but how their electrochemical properties are changed by nano-fibrillization has been little studied. Therefore, we decided to clarify the relationship between the size of CNFs and the electrochemical impedance properties of the CNF suspensions containing un-fibrillated fibers, which were prepared by a wet refinement system. The fiber diameter remained constant as the number of mechanical treatments (hereafter referred to as the “number of collisions”) increased. On the other hand, the cumulative medium volume diameter, D50, defined as the apparent fiber length (hereafter referred to as the “fiber length”, in microns), significantly decreases with the increasing number of collisions. The rheo-impedance |Z| of the CNF suspension remained nearly constant in the intermediate frequency range of 103–106 Hz, even if the internal structure of the system was deformed by the increasing shear rate. This means that the electrochemical properties of the CNFs are independent of the changes in the macroscopic aggregation structure. Furthermore, the internal resistance R1 calculated from the impedance |Z| characteristics (Nyquist plot) became decreased with the increasing number of collisions, indicating a proportional relationship between the resistance R1 and the CNF fiber length, D50. This suggests that R1 related to the resistance caused by the electrolyte in the suspensions or the protons dissociated by the hydration of the hydroxyl groups of the cellulose molecule as they move across the gaps between the microfibrils. Based on these results, it appears that the electrochemical properties of the CNF suspensions are independent of the changes in the macroscopic aggregation structure and simply depend on the fiber length, in other words, the electrochemical properties are a useful method for indirectly evaluating the fiber length of the CNFs.
期刊介绍:
Cellulose is an international journal devoted to the dissemination of research and scientific and technological progress in the field of cellulose and related naturally occurring polymers. The journal is concerned with the pure and applied science of cellulose and related materials, and also with the development of relevant new technologies. This includes the chemistry, biochemistry, physics and materials science of cellulose and its sources, including wood and other biomass resources, and their derivatives. Coverage extends to the conversion of these polymers and resources into manufactured goods, such as pulp, paper, textiles, and manufactured as well natural fibers, and to the chemistry of materials used in their processing. Cellulose publishes review articles, research papers, and technical notes.