Benchmarking Cellulose Nanocrystals: From the Laboratory to Industrial Production

Abstract

Abstract:The renewability, biocompatibility and mechanical properties of cellulose nanocrystals (CNCs) have made them an attractive material for numerous composite, biomedical and rheological applications. However, for CNCs to shift from laboratory curiosity to commercial applications, researchers must transition from CNCs extracted at the bench scale to material produced at an industrial scale. There are a number of companies currently producing kilogram to ton per day quantities of sulfuric acid-hydrolyzed CNCs, as well as other nanocelluloses, as described herein.With the recent intensification of industrially produced CNCs, the variety of cellulose sources, hydrolysis methods and purification procedures, characterization of these materials becomes critical. This has further been justified by the past two decades of research which demonstrate that CNC stability and behaviour is highly dependent on surface chemistry, surface charge density and particle size. This work outlines key test methods that should be employed to characterize these properties to ensure a "known" starting material and consistent performance.Of the sulfuric acid-extracted CNCs examined, industrially produced material compared well with laboratory-made CNCs, exhibiting similar charge density, colloidal and thermal stability, crystallinity, morphology and self-assembly behaviour. In addition, it was observed that further purification of CNCs, using Soxhlet extraction in ethanol, had minimal impact on nanoparticle properties and is unlikely to be necessary for many applications. Overall the current standing of industrially produced CNCs is positive suggesting that the evolution to commercial scale applications will not be hindered by CNC production.

One-Pot Water-Based Hydrophobic Surface Modification of Cellulose Nanocrystals Using Plant Polyphenols

“…CNCs used in this work were produced industrially from bleached Kraft pulp by CelluForce Inc. 43 The CNCs are stable in aqueous suspension because their surface sulfate half ester groups impart electrostatic 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 6 repulsion (sulfur content is 0.81 ± 0.03 g/100 g CNC which is approximately 0.45 charges/nm 2 ). CNCs were received as a spray dried powder in the neutral sodium-form ( Figure 1a) and were easily redispersed in water with sonication ( Figure 1b).…”

“…28,43,50 The theoretical O/C ratio for pure cellulose is 0.83, for unmodified CNCs the measured ratio was 0.75, for CNC-TA it was 0.83 and for CNC-TA-DA it was 0.30. This follows the expected trend with decylamine addition where the O/C ratio drops significantly due to the addition of alkylamine chains with no oxygen.…”

Fractionation of cellulose nanocrystals: enhancing liquid crystal ordering without promoting gelation

“…With today's prominent role of nanorods and their organization in a variety of advanced materials 2,3 , the phenomenon has also acquired key industrial relevance. Cellulose nanocrystals (CNCs) constitute a class of nanorods that currently attracts considerable attention both from academia [4][5][6][7] and industry [8][9][10] for reasons in addition to the fact that they can be sustainably produced from plants or other bioresources. CNCs are often conveniently approximated as cylindrical rods of crystalline cellulose with a diameter d of a few nanometers and a length L on the order of a hundred nanometers, although the true shape may be closer to an irregular twisted beam 11,12 .…”

“…The second deviation-of critical importance for largescale control of the self-organization 18 and therefore for applications-is that, frequently, a completely liquid crystalline sample cannot be reached in practice because w 1 > w g , the CNC mass fraction at which the system turns into a macroscopic gel, which is often considered a kinetically arrested state 8,15,[19][20][21][22] . The rheological data that we present below confirm that the sample at w > w g is a physical gel; hence, the transition is a percolation phenomenon 23 , i.e., a continuous network of connected rods is established that spans the macroscopic sample and prevents the system from flowing.…”

Synthetic Strategies for the Fabrication of Cationic Surface-Modified Cellulose Nanocrystals

“…Given CNCs' exceptional physical and chemical properties as well as future commercialization prospects, this recently led to their industrial production in North America, Japan, and Europe [13,14]. In addition to the production of CNCs at an affordable quantity, obtaining CNC batches with comparable sizes and properties [15] remains a top priority in order to meet the high demand of the CNC community for the design of multifunctional CNCs for commercial applications.…”