Calculated phase diagrams for cellulose/ammonia/ammonium thiocyanate solutions in comparison to experimental results

Frey, Margaret W.; Theil, Michael H.

doi:10.1023/b:cell.0000014771.69377.3d

Cited by 11 publications

(10 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Based on review of literature on polymer dissolution (Miller-Chou and Koenig 2003) and phase behavior in cellulose solutions (Frey et al 1996a, b;Frey and Theil 2004) it was hypothesized that dissolution of cellulose was occurring more rapidly than dispersion of cellulose via mixing. The rapid dissolution was leading to regions of locally high concentration or gels which 1% 2% 3% 4% 5% 6% 7% cellulose concentration (%w/w)…”

Section: Resultsmentioning

confidence: 99%

Dissolution of cellulose in ethylene diamine/salt solvent systems

Frey

Gould

2006

Cellulose

Self Cite

View full text Add to dashboard Cite

Investigation of the dissolution of cellulose in Ethylene Diamine (EDA)/Potassium thiocyanate (KSCN) solutions by infrared spectroscopy (FTIR) and thermal analysis (DSC) indicated that changes to the solvent during freeze thaw cycling of mixtures was consistent with increased interaction between cellulose and solvent. Thermal transitions in the system, however, occurred at temperatures outside the range used in thermal cycling to promote dissolution. Further exploration of the dissolution and mixing process indicated that mixing was the limiting step in solution formation. The dissolution of two types of cellulose with different molecular weights (Degree of Polymerization (DP)=210 and >1000) was studied using EDA/ KSCN solution as the solvent. The solubility and the dissolution rate of cellulose depended on both the solvent composition and cellulose molecular weight. Cellulose could dissolve faster in the solvent with lower salt concentration but the highest cellulose concentration was obtained in the solvent with 30$35% KSCN. Rheological measurements showed that cellulose solutions exhibited viscous solution behavior at low KSCN concentration but primarily elastic behavior at high salt concentration.

show abstract

Section: Resultsmentioning

confidence: 99%

Dissolution of cellulose in ethylene diamine/salt solvent systems

Frey

Gould

2006

Cellulose

Self Cite

View full text Add to dashboard Cite

show abstract

“…Cellulose persistence length varied with NH 4 SCN concentration in the solvent and the most extended chain conformation was measured when NH 3 /NH 4 SCN composition was 24.5/75.5 (w/w). Calculated phase diagrams for the cellulose/NH 3 /NH 4 SCN system predict that increased persistence length will strongly influence the formation of a gel phase 11…”

Section: Resultsmentioning

confidence: 99%

Rheology of cellulose/KSCN/ethylenediamine solutions and coagulation into filaments and films

Frey

Chan²,

Carranco

2005

J Polym Sci B Polym Phys

Self Cite

View full text Add to dashboard Cite

Dissolution of cellulose in ethylenediamine/potassium thiocyanate (KSCN) was studied as a function of cellulose and KSCN concentration. Concentrations of up to 9% (w/w) cellulose were obtained. Large variations in solution rheology with salt and cellulose concentration were observed, and phases including flowing solutions and gels were identified visually. Rheological data indicated that viscosity decreased with increasing salt or cellulose concentration in certain composition ranges. Viscosity decrease with concentration increase is associated with either onset of liquid crystalline ordering or phase separation in the system. Both of these are quite likely in the cellulose/ethylenediamine/KSCN system, depending on composition. Additionally, comparison of loss (G′′) and storage (G′) moduli confirmed that compositions that exhibited gel behavior at zero shear became liquid at shear rates as low as 1 Hz. Solutions were coagulated into filaments and films using ethanol (CH3CH2OH) and methanol (CH3OH). Infrared spectroscopy (FTIR) indicated that significant quantities of KSCN salt remained in the fibers and films after coagulation. Subsequent washing removed residual KSCN and improved physical properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2013–2022, 2005

show abstract

“…This can be realized in using a suitable solvent [11][12][13], which must be able to break the extensive system of hydrogen bonds along the cellulose polymer chain without degrading or inducing derivate reactions of the polymer chains.…”

Section: Cellulose Aerogel Monolithsmentioning

confidence: 99%

Monoliths and Fibrous Cellulose Aerogels

Ratke¹

2011

Aerogels Handbook

View full text Add to dashboard Cite

Cellulose aerogels can be produced by using several methods, yielding materials with extremely low densities. Their structure can be described as a type of nanofelt, which means that the elementary fibrils of cellulose are arranged in a random three-dimensional (3D) network. Aerogels made either by freeze or supercritical drying of dissolved cellulose nanofibrils can be transformed into filaments, establishing the first open porous filament for possible textile applications. They can also be converted to carbon aerogel monoliths and filaments opening up new fields of application. The review describes the different methods developed by several research groups worldwide to produce low density cellulose monoliths and filaments. It presents the microstructures obtained with various methods and the properties of cellulose aerogels. IntroductionCellulose in its various modifications is a natural linear macromolecule produced mainly by plants in huge amounts per year, approximately a billion tons. Chemically it is a chain of 1-4-linked b-D-glucopyranose, which means that the b-D-glucopyranose ring in its chair conformation is connected via oxygen bridges to a linear chain and hydrogen bonds stiffen the chain. Crystalline cellulose can exhibit essentially four crystallographically distinct polymorphic modifications [1]. The walls of plant cells produce cellulose from glucose units which are a result of photosynthesis. Cellulose fibers in the cell walls together with hemi-cellulose and lignin are responsible for the extremely good mechanical properties of this three-phase composite allowing especially trees to grow to huge sizes. For commercial applications, cellulose is obtained from cotton, bast fibers, flax, hemp, sisal, and jute or wood. The production of cellulose fibers generally needs a separation of the cellulose from lignin and hemicellulose and other constituents of plants cells. This can be done chemically and processes were then developed to produce a viscous liquid that can be spun. Regeneration leads to fibers consisting of pure cellulose (rayon and viscose process [2,3]). Many derivatives of cellulose in the form of esters and ethers were developed having a broad variety of applications (e.g., cellulose-acetates and nitrocellulose). Cellulose is the L. Ratke

show abstract

Calculated phase diagrams for cellulose/ammonia/ammonium thiocyanate solutions in comparison to experimental results

Cited by 11 publications

References 14 publications

Dissolution of cellulose in ethylene diamine/salt solvent systems

Dissolution of cellulose in ethylene diamine/salt solvent systems

Rheology of cellulose/KSCN/ethylenediamine solutions and coagulation into filaments and films

Monoliths and Fibrous Cellulose Aerogels

Contact Info

Product

Resources

About