Cellulose Nanofiber Orientation in Nanopaper and Nanocomposites by Cold Drawing

Sehaqui, Houssine; Mushi, Ngesa Ezekiel; Morimune, Seira; Salajková, Michaela; Nishino, Takashi; Berglund, Lars A.

doi:10.1021/am2016766

Cited by 311 publications

(265 citation statements)

References 33 publications

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“…Reorientation of nanofibers has been reported for specimens that were being drawn at a wet state prior to drying (Sehaqui et al 2012). Here, the nanofibers reoriented because the hydrogen bonding was affected by the presence of water molecules which also acted as plasticizer between nanofibers.…”

Section: Temperature Dependent Dielectric Spectroscopymentioning

confidence: 94%

Toughening mechanisms in cellulose nanopaper: the contribution of amorphous regions

Mao

Meng

et al. 2017

Cellulose

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Cellulose nanopaper is a strong and tough fibrous network composed of hydrogen bonded cellulose nanofibres. Upon loading, cellulose nanopaper exhibits a long inelastic portion of the stress-strain curve which imparts high toughness into the material. Toughening mechanisms in cellulose nanopaper have been studied in the past but mechanisms proposed were often rather speculative. In this paper, we aim to study potential toughening mechanisms in a systematic manner at multiple hierarchical levels in cellulose nanopaper. It was proposed that the toughness of cellulose nanopaper is not, as is often assumed, entirely caused by large scale inter-fibre slippage and reorientation of cellulose nanofibres. Here it is suggested that dominant toughening mechanism in cellulose nanopaper is associated with segmental motion of molecules facilitated by the breakage of hydrogen bonds within amorphous regions .

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Section: Temperature Dependent Dielectric Spectroscopymentioning

confidence: 94%

Toughening mechanisms in cellulose nanopaper: the contribution of amorphous regions

Mao

Meng

et al. 2017

Cellulose

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“…Orientation can be induced in NFC films by drawing, as shown previously. 58,59 Therein, special care was necessary to draw neat NFC films in the wet state due to their mechanical weakness. In our case, the drawing has been considerably easier as the films are significantly stronger in the wet state than neat NFC films.…”

Section: Mechanism Of Crosslinkingmentioning

confidence: 99%

Water-Resistant, Transparent Hybrid Nanopaper by Physical Cross-Linking with Chitosan

et al. 2015

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ABSTRACT. One of the major, but often overlooked, challenges towards high end applications of nanocelluloses is to maintain their mechanical stability under hydrated conditions. As such, permanent covalent crosslinking or surface hydrophobization are viable solutions provided that neither processability nor interfibrillar bonding is compromised. Here we show an alternative based on physical crosslinking of nanofibrillated cellulose (NFC, also denoted as microfibrillated cellulose, MFC, and cellulose nanofibers, CNF) with chitosan for the preparation of transparent films. Transparency (~ 80 % throughout the visible spectrum) is achieved by suppressing aggregation and carefully controlling the mixing conditions: Chitosan dissolves in aqueous medium at low pH and under these conditions the NFC/chitosan mixtures form easily processable hydrogels.A simple change in the environmental conditions (i.e. an increase of pH) reduces hydration of chitosan promoting multivalent physical interactions between NFC and chitosan over those with water, resulting effectively in crosslinking. Films of NFC/chitosan 80/20 w/w show excellent mechanical properties in the wet state, with a tensile modulus of 4 and 14 GPa at low (0.5 %) and large (16 %) strains, respectively and an ultimate strength of 100 MPa (with corresponding maximum strain of 28 %). Remarkably, a strength of 200 MPa (with maximum strain of 8%) is measured at 50 % air relative humidity. We expect that the proposed, simple concept opens new pathways toward NFC-based material utilization in wet or humid conditions, a challenge that has remained unresolved.

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“…High-strength (Sehaqui et al 2012) transparent (Nogi et al 2009) nanopapers with embedded functionalities Morales-Narváez et al 2015) and matrix properties ) can be obtained through simple vacuum filtration. The porosities of the fabricated nanopapers can be increased by replacing the water medium with solvents that are less polar (Sehaqui et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Mechanical fabrication of high-strength and redispersible wood nanofibers from unbleached groundwood pulp

et al. 2017

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In the past, the direct production of lignincontaining nanofibers from wood materials has been very limited, and nanoscale fibers (nanocelluloses) have been mainly isolated from chemically delignified, bleached cellulose pulp. In this study, we have introduced a newly adapted, heat-intensified disc nanogrinding process for the enhanced nanofibrillation of wood nanofibers (WNF) with a high lignin content (27.4 wt%). The WNF produced this way have many unique and intriguing properties in their naturally occurring form, for example, being able to be dispersed in ethanol and having ethanol solution viscosities higher than water solution viscosities. When WNF nanopapers were formed with ethanol, the properties of the nanofibers were recoverable without a notable decrease in the viscosity or mechanical strength after redispersing them in water. The preservation of lignin in the WNF was noticed as an increase in the water contact angles (89°), the rapid removal of water in the fabrication of the nanopapers, and the enhanced strength of the nanopapers when subjected to high pressure and heat. The nanopapers fabricated from the WNF were mechanically stable, having an elastic modulus of 6.2 GPa, a maximum stress of 103.4 MPa, and a maximum strain of 3.5%. Throughout the study, characteristics of the WNF were compared to those of the delignified and bleached reference cellulose nanofibers. We envision that the exciting characteristics of the WNF and their lower cost of production compared to that of bleached cellulose nanofibers may offer new opportunities for nanocellulose and biocomposite research.

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Cellulose Nanofiber Orientation in Nanopaper and Nanocomposites by Cold Drawing

Cited by 311 publications

References 33 publications

Toughening mechanisms in cellulose nanopaper: the contribution of amorphous regions

Toughening mechanisms in cellulose nanopaper: the contribution of amorphous regions

Water-Resistant, Transparent Hybrid Nanopaper by Physical Cross-Linking with Chitosan

Mechanical fabrication of high-strength and redispersible wood nanofibers from unbleached groundwood pulp

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