Cellulose‐based fibers from liquid crystalline solutions. III. Processing and morphology of cellulose and cellulose hexanoate esters

Davé, Vipul; Glasser, Wolfgang G.

doi:10.1002/app.1993.070480411

Cited by 20 publications

(5 citation statements)

References 33 publications

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“…This challenge could be overcome with a continuous printing approach, yielding a closed 3D ring structure. More critically, we point out that the intrinsic trend of LC (blend) solutions to form fibrils in elongational flow 69 could not be eradicated completely in the DIW process.…”

Section: ■ Results and Discussionmentioning

confidence: 87%

Lignin in Bio-Based Liquid Crystalline Network Material with Potential for Direct Ink Writing

Gleuwitz

Sivasankarapillai

Siqueira

et al. 2020

ACS Appl. Bio Mater.

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The flow-induced supramolecular arrangement, or band texture, present in water-soluble anisotropic films prepared from blend solutions of hydroxypropyl cellulose and organosolv lignin is locked via esterification with bio-based polycarboxylic acids. Subsequent to shear casting of the blend solutions, the chemical cross-linking with citric acid-based cross-linkers and a dimerized fatty acid yields water-insoluble, anisotropic films prone to swelling in water. The liquid crystalline networks are analyzed by means of polarized optical microscopy, tensile testing, Fourier transform infrared, and swelling experiments. Depending on the cross-linker, the dry “banded” films reach up to 3.5 GPa in tensile modulus, 80 MPa in tensile strength along the shear direction, and 5 MJ/m3 toughness across the shear direction. Films are softened upon water uptake causing a reversible extinguishment of the banded texture without interfering with the specimens’ anisotropy. Rheological studies point to the applicability of highly concentrated blend solutions to direct ink writing. The implementation of the findings to the additive manufacturing of cross-linked 3D structures demonstrates the potential of a resource-friendly processing of fully bio-based materials.

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Section: ■ Results and Discussionmentioning

confidence: 87%

Lignin in Bio-Based Liquid Crystalline Network Material with Potential for Direct Ink Writing

Gleuwitz

Sivasankarapillai

Siqueira

et al. 2020

ACS Appl. Bio Mater.

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“…Its lyotropic and thermotropic characteristics have been well documented. Although the lyotropic properties of many alkyl-substituted cellulosic polymers were reported by Gray , and by Glasser, , their thermotropic properties have not been thoroughly investigated. In this regard, HPC is a good vehicle for such studies.…”

Section: Introductionmentioning

confidence: 99%

Morphological Development in Alkyl-Substituted Semiflexible Polymers

Lee¹,

Pearce²,

Kwei³

1997

Macromolecules

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Nonsymmetrically substituted semiflexible polymers were synthesized by reacting (hydroxypropyl)cellulose (HPC) with hexyl, octyl, dodecyl, and octadecyl isocyanates. X-ray diffraction studies indicate that the polymer chains are assembled in regular, layered arrays. Polymers with six and eight carbons in the side chains (C6HPC and C8HPC) showed spherulitic structures typical of common crystalline polymers when examined by a polarized optical microscope (POM), whereas liquid crystalline (LC) textures were observed for C12HPC and C18HPC. When the polymers were slowly cooled from the melt, crystalline (C) textures could be obtained for C12HPC and C18HPC at preselected temperatures slightly higher than the corresponding (isotropic f LC) transition temperatures determined by DSC cooling scans. Upon further cooling, liquid crystalline structures appeared at temperatures 5-6°C lower. The unusual POM observations are in contrast to conventional thermal transitions reported for liquid crystalline polymers, where the isotropic f LC transition takes place at a temperature higher than that of the LC f C transition, but are consistent with Keller's studies on another liquid crystalline polymer.

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“…On the other hand, in anisotropic polymer solutions a critical concentration appears, above which a further increase in concentration reduces viscosity that results from spontaneous ordering of polymer chains up to the saturation concentration at which a partial solidification occurs 26–33…”

Section: Resultsmentioning

confidence: 99%

Physical properties of lyocell fibers spun from different solution‐dope phases

Kim

Lee

et al. 2001

J of Applied Polymer Sci

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ABSTRACT:The hydration number (n) of NMMO hydrates has a significant effect on the rheological properties and phase of the cellulose solutions in the hydrates. The physical properties of the lyocell fibers spun from the cellulose solutions in NMMO hydrates with different values of n were investigated relative to the phase of the solution dope. NMMO hydrate with n ϭ 1.1 could not fully dissolve cellulose, resulting in a heterogeneous solution. NMMO hydrate with n ϭ 0.72 produced a mesophase solution that exhibited a good spinnability. When NMMO hydrates with n ϭ 0.72 and 1.0 were used, the lyocell fiber spun from 15 wt % solution dope gave higher tensile strength than that spun from 12 wt % solution dope. NMMO hydrate with n ϭ 1.0 produced a lyocell fiber whose tensile strength was slightly affected by spin-draw ratio but the tensile strength of the lyocell fiber prepared from NMMO hydrate with n ϭ 0.72 was monotonically increased with increasing spin-draw ratio. Further, the latter gave higher birefringence. The lyocell fiber spun from 15 wt % solution in NMMO hydrate with n ϭ 0.72 produced finely fibrillated structures. When treated with sonic wave the lyocell fiber prepared from 15 wt % cellulose (DP w 940) solution in NMMO hydrate with n ϭ 0.72 yielded the most serious fibrillation on the fiber surface.

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Cellulose‐based fibers from liquid crystalline solutions. III. Processing and morphology of cellulose and cellulose hexanoate esters

Cited by 20 publications

References 33 publications

Lignin in Bio-Based Liquid Crystalline Network Material with Potential for Direct Ink Writing

Lignin in Bio-Based Liquid Crystalline Network Material with Potential for Direct Ink Writing

Morphological Development in Alkyl-Substituted Semiflexible Polymers

Physical properties of lyocell fibers spun from different solution‐dope phases

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