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Holocelluloses, TEMPO-oxidized holocelluloses, and TEMPO-oxidized cellulose nanofibrils were prepared from buckwheat and rice husks to characterize the cellulose microfibril morphologies and holocellulose molar masses. The buckwheat and rice husks had ash contents of 0.8% and 23%, respectively. All TEMPO-oxidized holocelluloses had cellulose I crystal structures. TEMPO-oxidized cellulose nanofibrils...
Surface C6-carboxylated cellulose nanofibrils (TCNF-COONa) were prepared from wood cellulose by TEMPO/NaBr/NaClO oxidation in water at pH 10 and successive mechanical disintegration of the oxidized cellulose in water. Aqueous TCNF dispersions with magnesium and calcium carboxylate groups, TCNF-COOMg and TCNF-COOCa, respectively, were prepared in high yields of 85–90% from aqueous TCNF-COONa dispersion...
Three chlorine reagents (NaClO solution, solid sodium dichloroisocyanurate (NaDCC), and solid NaClO·5H2O) were used as primary oxidants in the TEMPO/NaBr oxidation of wood cellulose in water. The active chlorine content of NaDCC was stable during storage, while that of NaClO solution decreased by 20% after storage in a tightly closed bottle for 1 year. As NaClO·5H2O has a melting point of ~ 25 °C,...
Catalytic oxidation using N-oxyl radicals in water at pH 10 was applied to wood cellulose to determine the influence of different N-oxyl radical chemical structures on the reaction kinetics and structures of oxidized celluloses. 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO), 2-azaadamantane N-oxyl (AZADO), 1-methyl-AZADO (1-Me-AZADO), 9-azanoradamantane N-oxyl (Nor-AZADO), and 1,5-dimethyl-9-azanoradamantane...
Transparent films of cellulose nanofibrils (CNFs) with high moduli and low thermal expansion coefficients have attracted significant attention for use as packaging films or as substrates for flexible electronics. In the present study, the thermal and electrical properties of 2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized CNF (T-CNF) films with quaternary alkyl ammonium (QAs) carboxylates were...
A surface-carboxylated nanocellulose was prepared from wood cellulose by catalytic oxidation with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). The fibrous TEMPO-oxidized cellulose with sodium carboxylate groups (TOC-Na) was surface-hydrophobized by counterion exchange with tetra-n-butylammonium [TOC-N(n-Bu)4]. This fibrous TOC-N(n-Bu)4 was mechanically disintegrated in water and N,N-dimethylformamide...
Size-exclusion chromatography using multi-angle laser-light scattering, refractive index, and ultraviolet absorption (SEC/MALLS/RI/UV) detection was applied to Japanese cedar (JC) and eucalyptus (E) powders after delignification (D), extraction with 4% NaOH (H), and acid hydrolysis (A), with different sequences of the D, H, and A treatments. All the delignified wood samples were dissolved in 8% (w/w)...
Aqueous nanocellulose dispersions were prepared from wood cellulose by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. The obtained TEMPO-oxidized cellulose was converted into TEMPO-oxidized cellulose nanofibrils (TOCNs) of different lengths by controlling the nanofibrillation conditions in water or using dilute acid hydrolysis. The average lengths and length distributions...
ZnO particle/water and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN)/water dispersions were mixed at various ratios under stirring. The aqueous ZnO/TOCN mixtures were sonicated, cast, and dried to prepare ZnO/TOCN composite films with various ZnO/TOCN weight ratios. The ZnO contents of the films were controlled to 0–50% (w/w). When the ZnO content was increased...
The influence of coexisting salt in 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of wood cellulose in water at pH 10 for 100 min was investigated, in which Na2SO4 was partly used in place of NaBr in the conventional TEMPO/NaBr/NaClO oxidation system. The amount of NaBr could be reduced from 1 to 0.2 mmol/g-wood cellulose by adding 0.4 mmol/g Na2SO4. This introduced a carboxylate...
Hemp bast (α-cellulose 79.4%, Klason lignin 4.9%) was directly oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation in water at pH 10 and room temperature for 2 h. The level of added NaClO in oxidation varied from 5 to 30 mmol/g (based on dry weight of hemp bast). Weight recovery ratios of the TEMPO-oxidized hemp bast celluloses were in the range of 81–91%, and their...
Six types of CNCs with different sizes were prepared from tunicins by sulfuric acid hydrolysis and subsequent sonication in water. The size distributions of CNCs were comprehensively evaluated by turbidimetry, small angle X-ray scattering, and microscopy to predict their intrinsic viscosities. Experimental intrinsic viscosities [η] of the CNC dispersions were evaluated by shear viscosity measurement,...
Softwood and hardwood bleached kraft pulps (SBKP and HBKP, respectively) and highly crystalline native celluloses such as algal, tunicate, bacterial and cotton lint celluloses were dissolved in 8 % (w/v) LiCl/N,N-dimethylacetamide (DMAc) after ethylenediamine (EDA) pretreatment. Complete dissolution of SBKP and other highly crystalline native celluloses in 8 % LiCl/DMAc was achieved after solvent...
The use of size-exclusion chromatography in combination with multi-angle laser-light scattering analysis (SEC–MALLS) can provide useful information pertaining to the molecular mass parameters of wood celluloses and hemicelluloses. When wood holocelluloses containing significant amounts of hemicelluloses were soaked in ethylenediamine (EDA) and subjected to sequential EDA-removal and solvent-exchange...
2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs) and poly(acrylamide) (PAM) with sodium carboxylate groups (TOCN-COONa and PAM-COONa, respectively) were converted to TOCN and PAM with protonated carboxyl groups (TOCN-COOH and PAM-COOH, respectively). Transparent and flexible PAM-COOH/TOCN-COOH, PAM-COONa/TOCN-COOH, and PAM-COOH/TOCN-COONa composite films were prepared...
Poly(acrylamides) (PAMs) with various anionic and cationic charge densities from −1.64 to +0.98 meq/g but similar molecular weights were synthesized through radical polymerization. One of the aqueous PAM solutions and an aqueous dispersion of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN) were mixed at various PAM/TOCN weight ratios, and self-standing PAM/TOCN composite...
A round robin on GPC of a wide range of different pulp samples was conducted among leading groups in cellulose analysis. The aim was to survey the status quo of the methods available to date. The pulp samples covered not only fully-bleached dissolving pulps but also bleached paper pulps and one unbleached sample. The methods applied were current state-of-the-art GPC with RI, MALLS, and viscosimetry...
Two cellouronic acids [sodium (1 → 4)-β-polyglucuronates, CUAs] and one 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized wood cellulose (TOC) became soluble in 8 % lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) after the methylation of C6 carboxyl groups in these samples using trimethylsilyldiazomethane (TMSD). The obtained solutions were diluted to 1 % LiCl/DMAc and subjected to...
Dispersion stability of TEMPO-oxidized cellulose nanofibrils (TOCNs) in water was investigated through both experimental and theoretical analyses to elucidate the critical aggregation concentration of different salts. The 0.1 wt% TOCN/water dispersions with various NaCl concentrations were evaluated by measuring light transmittance, viscosity under steady-shear flow, and the weight fraction of TOCN...
Never-dried 2,2,6,6,-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized wood celluloses (TOCs) with carboxylate contents of 1.0–1.7 mmol/g can be converted to TEMPO-oxidized cellulose nanofibrils (TOCNs) with homogeneous widths of ≈3 nm by mechanical disintegration treatment in water. However, oven-dried TOCs have low nanodispersibility in water. In this study, when TOC was reduced with NaBH4 under suitable...
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