Nanocellulose: Preparation, Dispersion, and Applications

sep 29 2020

Cellulose is the world’s most abundant biopolymer and is responsible for the strength in most plants. The key to the strength of this material is its structure: carefully ordered cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) build-up to form large, macromolecular constructs.1

These two types of nanocellulose have a high aspect ratio and show great promise for increasing strength in composite materials and stabilizing suspensions. CNFs and CNCs are also non-toxic, biocompatible, biodegradable, and are obtained from a sustainable source – an increasing focus in many industries.1,2

Preparation of Nanocellulose

The extraction of nanocellulose from plants commonly involves chemical treatment with strong acids, such as sulfuric acid. However, these strong acids are toxic and must be removed before the material can be used in food or for pharmaceutical applications.3 Recently, two new techniques to prepare CNCs have been developed: hydrothermal and microfluidization starting from commercially available microcrystalline cellulose. Both methods are chemical-free, and therefore suitable for many applications in the food and pharmaceutical field. Moreover, the environmental footprint is low and both methods can be easily scaled up for industrial use.3

Dispersion and Analysis

Once CNCs have been produced they are typically spray dried so they can be easily handled, transported, and stored for industrial processes. However, analysis of dispersions with spray-dried CNCs by static multiple light scattering and sedimentation kinetics using Formulcation’s Turbiscan technology has shown that this technique commonly results in poor redispersion, limiting the beneficial properties of these nanomaterials.2,4 By adding surfactants to CNC suspensions, researchers have created a modified foam-spray drying process, which has shown significant improvements in dispersibility. The modified dried CNC material showed excellent redispersion quality without the need for high shear mixing. Redispersion properties of the foam-spray dried powder were similar to the initial CNC suspension, confirmed by Turbiscan measurement.4 Unlike other particle dispersion analysis, Turbiscan technology can measure concentrated suspensions so actual products can be examined without the need for dilution.5

Applications of CNCs and CNFs

CNCs show great promise for use in the food and pharmaceutical industry to stabilize suspensions, reinforce packaging, and as functional food ingredients. Recently, emulsions were prepared using an ultrasound process and CNC. Compared to the conventional mechanic method (ultraturrax), the emulsion showed higher stability even for a smaller quantity of these nanoparticles.6 By incorporating inorganic minerals with CNFs, researchers have also developed hybrid nanocomposites with highly porous, lightweight structures and high strength. These nano-enhanced materials have shown potential for use in many applications including biomedical devices, renewable packaging materials, and fire-retardant nanocomposites.7

References and Further Reading

1. Dufresne A. (2013). Nanocellulose: A New Ageless Bionanomaterial. Materials Today. 
2. Mazloumi M., et al. (2018). Dispersion, Stability and Size Measurements for Cellulose Nanocrystals by Static Multiple Light Scattering. Cellulose.
3. Buffiere J., et al. (2017). The Chemical-Free Production of Nanocelluloses from Microcrystalline Cellulose and Their Uses as Pickering Emulsion Stabilizer. Carbohydrate Polymers. 
4. Esparza Y., et al. (2019). Effects of Additives on the Particle Morphology and Aqueous Dispersibility of Foam-Spray Dried Cellulose Nanocrystal Suspensions. Cellulose. 
5. (2020). Dispersibility – Redispersion. 
6. Dias Meirelles A.A., et al. (2020). Cellulose Nanocrystals from Ultrasound Process Stabilizing O/W Pickering Emulsion. Biological Macromolecules. 
7. Tenhunen T.M., et al. (2018). Enhancing the Stability of Aqueous Dispersions and Foams Comprising Cellulose Nanofibrils (CNF) with CaCO3 Particles. Nanomaterials.

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