How does the never-dried state influence the swelling and dissolution of cellulose fibres in aqueous solvent?

Abstract

The authors are grateful to the publisher, Springer, for letting the manuscript being archived in this Open Access repository. The final publication is available at http://www.springerlink.com/content/b0gq532711101228/International audienceThe 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 was evaluated by recovering insoluble fractions. The results show a contrasted picture towards the effect of the never-dried state on the swelling and the dissolution capacity depending on the origin of the fibres and the type of aqueous solvent. In the case of NMMO--water, the presence of water within and around the fibre does not seem to favour dissolution initiation but after 2 h of mixing the dissolution yield appears to be similar for either dried or never-dried state. The limiting factor for dissolution in NMMO--water is not the penetration of the solvent inside the cellulose fibres, but only the local concentration of NMMO molecules around the fibre. For NaOH--water, both optical microscopy observations on individual fibres and dissolution yield measurements show that the never-dried state is more reactive for softwood pulps and cotton linters and has no significant effect on hardwood pulps. In this case, the local decrease of solvent strength is counteracted by the opening of the structure in the never-dried state which should enable the Na+ hydrated ions to penetrate easier

Rheology of nanofibrillated cellulose/acrylate systems for coating applications

“…In addition, the diffusion of water is enhanced by the increased fibre surface compared to the fibres before fibrillation. Such phenomena were already described for wood pulp fibres in 8 % NaOH solutions at low temperatures (Spinu et al 2011). In that study, highly fibrillated fibres swelled much faster compared to larger fibres and at lower NaOH concentrations, only the fibrillated fibres swelled.…”

“…On the other hand, swelling of the NFC might be a reason. Swelling is very well reported for native dried and never-dried cellulose, dry NFC films and composites containing NFC, but not for suspended NFC (Eyholzer et al 2011;Ahola et al 2008;Spinu et al 2011). In general, water diffuses into the amorphous part of cellulose and causes swelling of the entire material (Aulin et al 2009).…”

Susceptibility of never-dried and freeze-dried bacterial cellulose towards esterification with organic acid

“…According to Le Chatelier's principle, the removal of water from the reaction will shift the equilibrium of the reaction to favour the production of more cellulose esters. It has also been reported that the starting form of cellulose (never-dried, partially dried or fully dried) affects the dissolution of cellulose in ionic liquid as the water molecules in the never-dried cellulose reduce the solvent quality (Spinu et al 2011). The estimated residual water content for both types of BC is tabulated in Table 2.…”

Morphological properties of nanofibrillated cellulose produced using wet grinding as an ultimate fibrillation process

“…Obviously, the use of neverdried cellulose, comparing to the once-dried, facilitates the fibrillation, since the drying promotes the irreversible hydrogen-bonding between nanofibrils, known as hornification [32]. However, the dry cellulose is much easier to transport.…”