10 research outputs found
Versatile synthesis of polysaccharide hydrogels using the Passerini and Ugi multicomponent condensations
Get PDFOptimization of conditions for 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion/sodium hypochlorite-catalyzed selective oxidation of the primary alcohol in 1-Monolaurin
No full textCharacteristics of TEMPO-oxidized cellulose fibril-based hydrogels induced by cationic ions and their properties
No full textQualitative evaluation of microfibrillated cellulose using the crill method and some aspects of microscopy
No full textOxidative polyaldehyde production: a novel approach to the conjugation of dextran with soy peptides for improved emulsifying properties
No full textAmine functionalization of cellulose nanocrystals for acid–base organocatalysis: surface chemistry, cross-linking, and solvent effects
No full text
Effect of xylan in hardwood pulp on the reaction rate of TEMPO-mediated oxidation and the rheology of the final nanofibrillated cellulose gel
No full textalkali-washed nanofibrillated cellulose (NFC) samples, obtained from hardwood kraft pulp, with different amounts of retained xylan were prepared to study the influence of xylan on the water-retention properties of NFC suspensions. In this study, NFC was produced using an oxoammonium-catalyzed oxidation reaction that converts the cellulosic substrate to a more highly oxidized material via the action of the nitroxide radical species 2,2,6,6-tetramethylpiperidine-1-oxyl. Reduction of the xylan content in NFC was achieved by cold alkali extraction of kraft pulp. The pulps were then oxidized to a set charge under constant chemical conditions, and the reaction time was determined. The xylan content of the feed pulp was found to have a large negative influence on the oxidation rate of the pulp, as the oxidation time shortened when xylan was removed, from 220Â min (for 25.2Â % xylan content) to 28Â min (for 7.3Â % xylan content). Following fibrillation by homogenization, the swelling of the NFC was determined by a two-point solute exclusion method. The distribution of hemicellulose over the fibril surface was observed by atomic force microscopy. Xylan was found to be distributed unevenly over the surface, and its presence increased the water immobilized within flocs of NFC, i.e., so-called network swelling. The swelling of the NFC had a large impact on its rheology and dewatering. Comparison of the morphological and swelling properties of the suspensions with their rheological and dynamic dewatering behavior showed that reducing the xylan content in NFC results in a weaker gel structure of the nanocellulose suspension. The results indicate that most of the water is held by the swollen structure by means of xylan particles trapped within the hemicellulose layer covering the fibril surface. Samples with high xylan content had high shear modulus and viscosity and were difficult to dewater.</p
