Effect of xylan in hardwood pulp on the reaction rate of TEMPO-mediated oxidation and the rheology of the final nanofibrillated cellulose gel
| Autor: | Katarina Dimic-Misic, Tapani Vuorinen, Hannes Orelma, Timo Pääkkönen, Thaddeus Maloney, Raili Pönni |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Materials science
animal structures Polymers and Plastics Dewatering 02 engineering and technology macromolecular substances engineering.material 010402 general chemistry 01 natural sciences Nanocellulose Reaction rate Alkali treatment Bacterial cellulose chemistry.chemical_compound Xylan Nanofibrillated cellulose medicine Organic chemistry Hemicellulose Cellulose TEMPO-mediated oxidation Pulp (paper) Birch technology industry and agriculture 021001 nanoscience & nanotechnology 0104 chemical sciences chemistry Kraft process Chemical engineering engineering Swelling medicine.symptom 0210 nano-technology Rheology |
| Zdroj: | Pääkkönen, T, Dimic-Misic, K, Orelma, H, Pönni, R, Vuorinen, T & Maloney, T 2016, ' Effect of xylan in hardwood pulp on the reaction rate of TEMPO-mediated oxidation and the rheology of the final nanofibrillated cellulose gel ', Cellulose, vol. 23, no. 1, pp. 277-293 . https://doi.org/10.1007/s10570-015-0824-7 |
| Popis: | alkali-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 220 min (for 25.2 % xylan content) to 28 min (for 7.3 % 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. |
| Databáze: | OpenAIRE |
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