Gel point as a measure of cellulose nanofibre quality and feedstock development with mechanical energy

Raj, Praveena; Mayahi, Alireza; Lahtinen, Panu; Varanasi, Swambabu; Garnier, Gil; Martin, Darren J.; Batchelor, Warren

doi:10.1007/s10570-016-1039-2

Cited by 51 publications

(41 citation statements)

References 43 publications

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“…The theory, methods and equations for the determination and calculation of connectivity threshold (U c ) and rigidity threshold of CNF from sedimentation experiments have been well described by Zhang et al (2012), Varanasi et al (2013) and Raj et al (2016). The connectivity threshold is defined as ''the boundary between the dilute and semi-dilute regions, the lowest volume fraction where the particles first form a continuous network'' (Varanasi et al 2013).…”

Section: Sedimentationmentioning

confidence: 99%

“…The use of sedimentation for aspect ratio estimation has been applied on uncharged and unmodified CNFs (Raj et al 2016;Varanasi et al 2013;Zhang et al 2012). It was suggested as a facile method for the quality control of CNF materials during processing (Raj et al 2016).…”

Section: Aspect Ratio Determination From Sedimentationmentioning

confidence: 99%

“…It was suggested as a facile method for the quality control of CNF materials during processing (Raj et al 2016). This method was herein adapted for electrostatically stabilised CMCNF and TCNF to estimate their aspect ratios.…”

Section: Aspect Ratio Determination From Sedimentationmentioning

confidence: 99%

“…Field emission scanning electron microscopic (FE-SEM) images and transmission electron microscopic (TEM) images were used for the assessment of fibril widths and morphology. The estimation of aspect ratio by connectivity threshold analysis using sedimentation, which has been applied on uncharged CNFs (Raj et al 2016;Varanasi et al 2013;Zhang et al 2012) was extended to CNF with surface charges, by taking advantage of the screening effect of salt medium on charged CNF. Finally, the viscoelastic properties of the aqueous suspensions of the CNFs were studied.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Sedimentationmentioning

confidence: 99%

Section: Aspect Ratio Determination From Sedimentationmentioning

confidence: 99%

Section: Aspect Ratio Determination From Sedimentationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2017

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“…For these reasons, CMNF suspensions can form yield-stress gels already at approx. 0.1-0.3% consistency (Varanasi et al 2013;Raj et al 2016;Li et al 2016;Arola et al 2018), and they have a strong tendency towards aggregation and flocculation (Karppinen et al 2012;Pääkkönen et al 2016;Hubbe et al 2017;Raj et al 2017;. Notice that highly crystalline and rigid nanoparticles having a length of a few hundred nanometers can be obtained from cellulose e.g.…”

Section: Introductionmentioning

confidence: 99%

The effect of consistency on the shear rheology of aqueous suspensions of cellulose micro- and nanofibrils: a review

Koponen

2019

Cellulose

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While the raw material type and the production method of cellulose micro- and nanofibrils (CMNFs) strongly affect the absolute values of the rheological parameters of their aqueous suspensions, the dependence of these parameters on consistency, c, is found to be uniform. The consistency index and yield stress of CMNF suspensions follow generally the scaling laws $$K \sim c^{2.43}$$K∼c2.43 and $$\tau_{y} \sim c^{2.26}$$τy∼c2.26, respectively, and a decent approximation for flow index is $$n = 0.30 \times c^{ - 0.43}$$n=0.30×c-0.43. The variability of reported scaling exponents of these materials is likely mainly due to experimental uncertainties and not so much due to fundamentally different rheology. It is suggested that the reason behind the apparently universal rheological behavior of CMNF suspensions is the strong entanglement of fibrils; the flow dynamics of typical CMNF suspensions is dominated by interactions between fibril flocs and not by interactions between individual fibrils. Graphic abstract

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Progress, Challenge, and Perspective of Fabricating Cellulose

Qiao

Wang

et al. 2022

Macromol. Rapid Commun.

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Cellulose as the most abundant biopolymers on Earth, presents appealing performance in mechanical properties, thermal management, and versatile functionalization. Developing fabrication methods to design functional materials and open new application areas. However, cellulose is hard to be dissolved or melt due to its recalcitrant property. Herein, the recent progress of fabricating cellulose is summarized. First, the unique hierarchical structure of cellulose is fully investigated and the resulted processability is analysed in directions of down to nanocellulose, dissolution, and thermoplastic processing. Then, the reported fabrication methods are summarized in three aspects: (1) self‐assembly from nano/micro cellulose suspensions, especially the formation of cellulose nanocrystals; (2) dissolution–regeneration–drying, covering spinning and solvent infusion processing; and (3) thermoplastic processing, focusing on the setup and the morphology changes of the prepared products. In each aspect, the flowchart of the fabrication method, the mechanism, fabricated products, and effects of processing parameters are explored. Finally, this review provides a perspective on the further direction of fabricating cellulose, especially the challenges toward mass production.

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Gel point as a measure of cellulose nanofibre quality and feedstock development with mechanical energy

Cited by 51 publications

References 43 publications

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

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

The effect of consistency on the shear rheology of aqueous suspensions of cellulose micro- and nanofibrils: a review

Progress, Challenge, and Perspective of Fabricating Cellulose

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