Morphological development of cellulose fibrils of a bleached eucalyptus pulp by mechanical fibrillation
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This study reports the production of cellulose nanofibrils (CNF) from a bleached eucalyptus pulp using a commercial stone grinder. Scanning electronic microscopy and transmission electronic microscopy imaging were used to reveal morphological development of CNF at micro and nano scales, respectively. Two major structures were identified: (1) highly kinked, naturally helical, and untwisted fibrils that serve as backbones of CNF networks, and (2) entangled, less distinctively kinked (or curled) and twisted “soft looking” nanofibrils. These two major structures appeared in different features of CNF network such as “trees”, “net”, “flower”, single fibril, etc. Prolonged fibrillation can break the nanofibrils into nanowhiskers from the untwisted fibrils with high crystallinity. Energy input for mechanical fibrillation is on the order of 5–30 kWh/kg. The gradual reduction in network size of CNF with time may be used to fractionate CNF.
KeywordsCellulose nanofibrils (CNF) Morphology Mechanical fibrillation/grinding Fiber/fibril network TEM imaging Nanowhisker
We acknowledge the financial supports by a USDA Agriculture and Food Research Initiative (AFRI) Competitive Grant (No. 2011-67009-20056) and Chinese Scholarship Council (CSC). The funding from these two programs made the visiting appointment of Wang at the USDA Forest Products Laboratory (FPL) possible. We also acknowledge Ann Masco of FPLL Paper Test Lab for FQA analysis. The authors also wish to thank Anne Kamata, SAIC-Frederick, Inc. for electron microscopy imaging. TEM imaging work was funded in whole or in part with federal funds from the National Cancer Institute, National Institutes of Health, under Contract No. HHSN261200800001E. The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the US Government.
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