Switchable ionic liquids enable efficient nanofibrillation of wood pulp

Berglund, Linn; Anugwom, Ikenna; Hedenström, Mattias; Aitomäki, Yvonne; Mikkola, Jyri‐Pekka; Oksman, Kristiina

doi:10.1007/s10570-017-1354-2

Cited by 30 publications

(25 citation statements)

References 32 publications

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“…The starting material was a commercial birch kraft pulp provided by SCA (Munksund, SE) and the nanofiber separation process has been described in detail in a previous study. 13 The chemical composition was 70 wt % cellulose, 21 wt % hemicellulose, and 5 wt % lignin (see Online Resource 1 of ref ( 13 )). The pulp was diluted to 1.5 wt % and dispersed using a shear mixer Silverson L4RT, (Silverson Machine Ltd., England) before fibrillation.…”

Section: Methodsmentioning

confidence: 99%

Thermal Conductivity of Cellulose Fibers in Different Size Scales and Densities

et al. 2021

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Considering the growing use of cellulose in various applications, knowledge and understanding of its physical properties become increasingly important. Thermal conductivity is a key property, but its variation with porosity and density is unknown, and it is not known if such a variation is affected by fiber size and temperature. Here, we determine the relationships by measurements of the thermal conductivity of cellulose fibers (CFs) and cellulose nanofibers (CNFs) derived from commercial birch pulp as a function of pressure and temperature. The results show that the thermal conductivity varies relatively weakly with density (ρ sample = 1340–1560 kg m –3 ) and that its temperature dependence is independent of density, porosity, and fiber size for temperatures in the range 80–380 K. The universal temperature and density dependencies of the thermal conductivity of a random network of CNFs are described by a third-order polynomial function (SI-units): κ CNF = (0.0787 + 2.73 × 10 –3 · T – 7.6749 × 10 –6 · T 2 + 8.4637 × 10 –9 · T 3 )·(ρ sample /ρ 0 ) 2 , where ρ 0 = 1340 kg m –3 and κ CF = 1.065·κ CNF . Despite a relatively high degree of crystallinity, both CF and CNF samples show amorphous-like thermal conductivity, that is, it increases with increasing temperature. This appears to be due to the nano-sized elementary fibrils of cellulose, which explains that the thermal conductivity of CNFs and CFs shows identical behavior and differs by only ca. 6%. The nano-sized fibrils effectively limit the phonon mean free path to a few nanometers for heat conduction across fibers, and it is only significantly longer for highly directed heat conduction along fibers. This feature of cellulose makes it easier to apply in applications that require low thermal conductivity combined with high strength; the weak density dependence of the thermal conductivity is a particularly useful property when the material is subjected to high loads. The results for thermal conductivity also suggest that the crystalline structures of cellulose remain stable up to at least 0.7 GPa.

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Section: Methodsmentioning

confidence: 99%

Thermal Conductivity of Cellulose Fibers in Different Size Scales and Densities

et al. 2021

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“…During the last decades, novel pretreatment methods using ionic liquids (IL) or organic solvents have been developed for the fractionation of biomasses. IL-based pretreatments have been demonstrated to be effective for the fractionation of several types of feedstock (Perez-Pimienta et al 2016) however, their large-scale use is limited, mainly owing to the high cost of ILs and the need for complex and expensive recycling processes (Berglund et al 2017).…”

Section: Introductionmentioning

confidence: 99%

NADES-based fractionation of biomass to produce raw material for the preparation of cellulose acetates

et al. 2020

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Waste biomass (agave bagasse) and native birch wood were used as raw materials for a novel fractionation and derivation process to produce cellulose acetates (CAs). During the first stage of the fractionation process, a significant amount of hemicelluloses and lignin were dissolved from the biomass using a natural deep eutectic solvent (NADES) that consisted of a mixture of choline chloride and lactic acid with the molar ratio of 1:9. Then, the residual solid material was delignified by bleaching it with a mixture of acetic acid and sodium chlorite. The fractionation process generated differently purified pulps (celluloses) which were converted to CAs. The crystallinity index, polymerization degree, chemical composition, and thermal properties of the differently purified pulps and CAs were analyzed to evaluate the efficacy of the acetylation process and to characterize the CAs. The chemical derivation of the differently purified cellulose samples generated CAs with different degrees of substitution (DSs). The more purified the cellulose sample was, the higher its DS was. Moreover, some differences were observed between the acetylation efficiencies of birch and agave bagasse. Typically, cellulose purified from birch by treating it with NADES followed by bleaching was acetylated more completely (DS = 2.94) than that derived from agave bagasse (DS = 2.45). These results revealed that using green solvents, such as NADES, to treat both agave bagasse (waste biomass) and birch wood, allowed pure fractions to be obtained from biomass, and thus, biomass could be valorized into products such as CAs, which present a wide range of applications.

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“…However, the effect of this treatment on the surface functionality of the resulting CNF was not studied. Switchable ionic liquid has also been used with the same aim of facilitating cellulose delamination into CNF material (Berglund et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Aqueous morpholine pre-treatment in cellulose nanofibril (CNF) production: comparison with carboxymethylation and TEMPO oxidisation pre-treatment methods

2017

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In this study, pulped cellulose fibres were pre-treated with aqueous morpholine prior to mechanical disruption in the production of cellulose nanofibrils (CNF). The properties of the morpholine pretreated CNF (MCNF) were closely compared with CNF obtained from carboxymethylation (CMCNF) and TEMPO-oxidation (TCNF) pre-treatment methods. An investigation of the swelling behaviours of cellulose in varying concentrations of morpholine revealed that there is a synergistic behaviour between morpholine and water in its ability to swell cellulose. As a result, cellulose pulp dispersed in 1:1 mole ratio of morpholine to water was well swollen and readily fibrillated by mechanical shear. Surface chemistry analyses indicated that the surface of the MCNF remained unmodified, compared to the CMCNF and TCNF which were modified with anionic groups. This resulted in only a slight decrease in crystallinity index and a minimal effect on the thermal stability of MCNF, compared to CMCNF and TCNF which showed marked decreases in crystallinity indices and thermal stabilities. The average widths of MCNF, CMCNF and TCNF, as measured from electron microscopic images, were broadly similar. The higher polydispersity of MCNF widths however led to a differential sedimentation and subsequent lower aspect ratio in comparison with CMCNF and TCNF as estimated using the sedimentation approach. Also, the presence of electrostatic repulsive forces, physical interactions/ entanglements and lower rigidity threshold of the CMCNF and TCNF resulted in higher storage moduli compared to the MCNF, whose elasticity is controlled by physical interactions and entanglements. Aqueous morpholine pre-treatment can potentially be regarded as an ecologically sustainable process for unmodified CNF production, since the chemical reagent is not consumed and can be recovered and reused.

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Switchable ionic liquids enable efficient nanofibrillation of wood pulp

Cited by 30 publications

References 32 publications

Thermal Conductivity of Cellulose Fibers in Different Size Scales and Densities

Thermal Conductivity of Cellulose Fibers in Different Size Scales and Densities

NADES-based fractionation of biomass to produce raw material for the preparation of cellulose acetates

Aqueous morpholine pre-treatment in cellulose nanofibril (CNF) production: comparison with carboxymethylation and TEMPO oxidisation pre-treatment methods

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