Abstract
Cellulose nanofibrils can be obtained from trees and have considerable potential as a building block for biobased materials. In order to achieve good properties of these materials, the nanostructure must be controlled. Here we present a process combining hydrodynamic alignment with a dispersion–gel transition that produces homogeneous and smooth filaments from a low-concentration dispersion of cellulose nanofibrils in water. The preferential fibril orientation along the filament direction can be controlled by the process parameters. The specific ultimate strength is considerably higher than previously reported filaments made of cellulose nanofibrils. The strength is even in line with the strongest cellulose pulp fibres extracted from wood with the same degree of fibril alignment. Successful nanoscale alignment before gelation demands a proper separation of the timescales involved. Somewhat surprisingly, the device must not be too small if this is to be achieved.
Highlights
Cellulose nanofibrils can be obtained from trees and have considerable potential as a building block for biobased materials
Cellulose fibres can be disintegrated[11,12] into individual fibrils or fibril bundles and, recently, films and filaments have been manufactured from CNF5,6,13–16
The properties obtained are far from the values reported for individual cellulose fibres liberated from wood[2,10] and it can be hypothesized that the fibrils have to be aligned and assembled in a controlled manner in order to make use of the potential of CNF
Summary
Cellulose nanofibrils can be obtained from trees and have considerable potential as a building block for biobased materials. The properties obtained are far from the values reported for individual cellulose fibres liberated from wood[2,10] and it can be hypothesized that the fibrils have to be aligned and assembled in a controlled manner in order to make use of the potential of CNF. As long as the timescales of the alignment and assembly process are correct, up or downscaling and parallelization of this process for industrial production are possible This will allow manufacturing of strong filaments from wood fibre raw material for future production of highperformance bio-composites as well as for textile production. In the latter context, the filaments could be a replacement product for cotton and industrially produced viscose and Lyocell, and thereby significantly contribute to a reduced environmental footprint by reduced use of organic solvents
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