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Dissolution of a number of cellulose samples in aqueous NaOH was investigated with respect to the influence of molecular weight, crystalline form and the degree of crystallinity of the source samples. A procedure for dissolving microcrystalline cellulose was developed and optimized, and then applied to other cellulose samples of different crystalline forms, crystallinity indices and molecular weights...
A series of pseudo amorphous cellulose samples were reacted with catalytic amounts of 2,2,6,6-tetramethyl-1-piperidine oxoammonium salt (TEMPO), sodium hypochlorite and sodium bromide in water. In all samples the primary alcohol groups were selectively oxidised into carboxyl groups, and several water-soluble polyglucuronic acid sodium salts were obtained with different molecular weights. With this...
The effect of enzymatic hydrolysis (EH) on the molecular characteristics as well as fractional composition of cellulose was studied using the direct size exclusion chromatography (SEC) analysis in sodium hydroxide. Bleached hardwood pulp was subjected to the action of the cellulase complex Celluclast™ supplemented with Novozyme 188™. The residues after the enzymatic treatment were fractionated by...
Molten salt hydrates proved to be alternative solvents to cellulose. Toinvestigate the reasons for this dissolving ability, information about thesolvent–cellulose interactions is essential. As well as 13CHR NMR, 7Li NMR was used to obtain further insight into thisproblem.After comparing several molten salt hydrates, the 7Li NMR spectrarevealed a smaller shielding of the lithium cation for not dissolving...
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...
New carboxymethylcellulose esters were developed with useful properties for oral dosage forms in drug delivery. Normally, commercial cellulose esters are used as the major excipients in oral dosage forms as a coating or a membrane. In applications involving compression tablets, cellulose esters are usually mixed with other more hydrophilic matrix components to facilitate dissolution of the active...
The solubilities of voriconazole, ketoconazole, and clotrimazole with and without hydroxybutenyl-β-cyclodextrin (HBenBCD) in aqueous media were examined. The solubility of these antifungal drugs was significantly improved by complexation with HBenBCD. Both the pH and the type of buffer used to adjust the medium pH had a very significant effect on drug solubilities and the apparent binding constants...
Ethylene diamine (EDA)/salt solvent systems can dissolve cellulose without any pretreatment. A comparison of the electrical conductivity of different salts in EDA was made at 25 °C, and conductivity decreased in the order of KSCN>KI>NaSCN at the same molar concentration. Among the salts tested, potassium thiocyanate (KSCN) was capable of dissolving both high molecular weight (DP>1000) and...
The swelling and dissolution mechanisms of several cellulose derivatives (nitrocellulose, cyanoethylcellulose and xanthate fibres) are studied in aqueous systems (N-methylmorpholine-N-oxide—water with various contents of water, hydroxide sodium—water) and in ionic liquids. The results are compared with the five modes describing the swelling and dissolution mechanisms of cotton and wood cellulose fibres...
Raw and refined flax, hemp, abaca, sisal, jute and ramie fibres are dipped into N-methylmorpholine N-oxide (NMMO)–water with various contents of water and into hydroxide sodium (NaOH)–water. The swelling and dissolution mechanisms of these plant fibres are similar to those observed for cotton and wood fibres. Disintegration into rod-like fragments, ballooning followed or not by dissolution and homogeneous...
Four wood pulps and a microcrystalline cellulose were dissolved in a NaOH 8%–water solution. Insoluble fractions and clear solution fractions were isolated by centrifugation and were observed by optical microscopy and transmission electron microscopy. Molecular weight distribution, carbohydrate composition and cellulose II content were measured. The dissolution of wood cellulose fibres in NaOH 8%–water...
The swelling and dissolution mechanisms of dry, never-dried and re-wetted Lyocell fibers were investigated using mixtures of N-methylmorpholine N-oxide and water with various contents of water (from monohydrate to 24% w/w). A radial dissolution starting from the outer layers was observed. Dissolution kinetics was dependent on the water content, the drying state and the spinning conditions. A buckling...
The swelling and dissolution capacity of dried and never-dried hardwood and softwood pulps and cotton linters was compared in two aqueous solvents, N-methylmorpholine-N-oxide (NMMO)-water at 90 °C with water contents ranging from 16 to 22% and NaOH—water at −6 °C with NaOH contents ranging from 5 to 8%. Swelling and dissolution mechanisms were observed by optical microscopy and dissolution efficiency...
Cellulose dissolution in water-based solvents is essential for processing of regenerated cellulose products such as fibres, films and particles. Cellulose dissolution in NaOH–urea aqueous solution has emerged as a simple and attractive alternative for processing cellulose solutions. However, this solvent requires energy intensive pretreatments such as milling or refining. In this paper we investigate...
The morphology and crystalline structure changes of cellulose during dissolution in 1-butyl-3-methylimidazolium chloride [(BMIM)Cl] were investigated by optical microscopy and synchrotron radiation wide-angle X-ray diffraction (WAXD). Neither swelling nor dissolution of cellulose was observed under the melting point of [BMIM]Cl. While the temperature was elevated to 70 °C, the swelling phenomenon...
To elucidate the role of urea in dissolution of cellulose in aqueous alkali-urea solvent, the dissolution process was monitored by differential scanning calorimetry and X-ray diffractometry. Urea had no direct interaction with cellulose in dissolution process, but promoted the decrease of crystallinity. Moreover, the addition of urea increased the dissolved fraction of cellulose in the solvent by...
Resveratrol is a highly biologically active phytoalexin, found in many plant materials that are common elements of the human diet, such as grapes, nuts, and red wine. The therapeutic or disease preventative potential of this natural polyphenolic antioxidant has been limited in part due to its poor aqueous solubility and low oral bioavailability. We hypothesized that solid dispersion of resveratrol...
A commercial dissolving pulp was treated with aqueous solutions containing 3, 5 and 7 % of an organometalic complex (nitren) with the aim to selectively extract xylan and study its impact on the conventional physical–chemical properties of the pulp. The influence of these treatments on the pulp dissolution in a moderate solvent (8 % NaOH aqueous solution) was assessed by measuring the dissolution...
Application of size exclusion chromatography (SEC) for the analysis of cellulose samples is often limited due to poor solubility in the solvent system N,N-dimethylacetamide/lithium chloride (DMAc/LiCl). Hence different activation or derivatization methods have been developed and published. Most of these methods are laborious, influence the molar mass distribution or do not support dissolution of manmade...
Cellobiose was used as a model compound for cellulose to study dissolution in aqueous systems with additives. The dissolution of cellobiose in alkali solutions is a typical exothermic enthalpy-driven process, confirming that lower temperature is beneficial for dissolution of cellulose in NaOH aqueous systems. OH− plays an important role in cellobiose dissolution by forming cellobiose–OH− hydrogen-bonded...
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