The investigation of rheological and strength properties of NFC hydrogels and aerogels from hardwood pulp by short catalytic bleaching (Hcat)
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Alkaline washed nanofibrillated cellulose (NFC) was obtained via TEMPO-mediation of hardwood pulp which had been short catalytically bleached (Hcat) under a controlled range of conditions. With careful combination of bleaching conditions, together with the subsequent alkali pre-treatment prior to TEMPO oxidation, it is possible to reduce xylan content of Hcat hardwood birch pulps as compared to traditional elemental chlorine free (ECF) bleaching. The defined amount of xylan is seen to affect the static water-holding and agglomeration state of the respective NFC. It is shown that colloidal interactions between the nanofibrils are dependent on the amount of water present in the NFC hydrogels as water retained within xylan induced swelling of the fibrils that resulted in a weaker aerogel structure.
KeywordsNanocellulose Hcat bleaching Aerogel Rheology Xylan content Water sorption Mechanical properties of aerogels
The authors thank Mr. Antton Lahnalammi for preparing some parts of bleached pulp and performing TEMPO-mediated oxidation of birch pulp samples and Christophe Pradille (Mat Xper, France) for the help in the uniaxial compression tests.
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