• Nanocellulose is a high-performance additive which is successfully used as rheology modifier, reinforcing agent and additive in manifold high-performance materials and applications.
• The nano-structured fibrils can be very efficiently isolated from any cellulose-containing source by high-power ultrasonic homogenization and milling.
• By sonication, a higher degree of fibrillation, higher nanocellulose yield, and thinner fibers can be achieved.
• The ultrasonic technology excels conventional methods of nanocellulose manufacture due to extreme cavitational high shear forces.

Ultrasonic Manufacture of Nanocellulose

High power ultrasonics contributes to the extraction and isolation of micro- and nano-cellulose from various sources of cellulosic materials such as wood, lignocellulosic fibers (pulp fibers), and cellulose containing residues.
To release the plant fibres from the source material, ultrasonic grinding and homogenization is a powerful and reliable method, that allows to process very large volumes. The pulp is fed into an inline sonoreactor, where ultrasonic high-shear forces break the cell structure of the biomass so that the fibrillous matter becomes available.
Figure 1 below shows a TEM image of “Never Dried Cotton” (NDC) submitted to enzymatic hydrolysis and sonicated with Hielscher’s UP400S for 20 minutes. [Bittencourt et al. 2008]

TEM image of “Never Dried Cotton” (NDC) submitted to enzymatic hydrolysis and sonicated with Hielscher’s UP400S for 20 minutes. [Bittencourt et al. 2008]

Figure 2 below shows a SEM image of a film of viscose, submitted to the enzymatic hydrolysis, followed by sonication with UP400S. [Bittencourt et al. 2008]

SEM image of a film of viscose, submitted to the enzymatic hydrolysis, followed by sonication with UP400S [Bittencourt et al. 2008]

Ultrasonic nanocellulose processing can be also successfully combined with the TEMPO-oxidized fiber treatment. In the TEMPO-process, cellulose nanofibers are produced by an oxidation system using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as catalyst, and sodium bromide (NaBr) and sodium hypochlorite (NaOCl). Research has proven that the oxidation efficiency is significantly improved when the oxidation is conducted under ultrasonic irradiation.

Ultrasonic Dispersion

Nanocellulose dispersions demonstrate an extraordinary rheological behaviour due to its high viscosity at low nanocellulose concentrations. This makes nanocellulose a very interesting additive as rheological modifier, stabilizer and gellant for various applications, e.g. in the coating, paper, or food industry. To express its unique properties, nanocellulose must be
Ultrasonic dispersing is the ideal method to obtain fine-size, single-dispersed nanocellulose. As nanocellulose is highly shear-thinning, ultrasound is the preferrable technology to formulate nanocellulosic suspensions as the coupling of high-power ultrasound into liquids creates extreme shear forces. (Click here to learn more about ultrasonic cavitation in liquids!)
After the synthesis of nanocrystalline cellulose, the nanocellulose is often ultrasonically dispersed into a liquid medium, e.g. a non-polar or polar solvent such as dimethylformamide (DMF), to formulate a final product (e.g. nanocomposites, rheological modifier etc.) As CNFs are used as additives in manifold formulations, a reliable dispersing is crucial. Ultrasonication produces stable and uniformly dispersed fibrils.

Industrial Ultrasonic Processing

Hielscher Ultrasonics supplies powerful and reliable ultrasonic technology from small lab ultrasonicators to bench-top systems and full-commercial industrial plant equipment. In Hielscher’s flowthrough sonoreactors, which are available at different sizes and geometries, optimal ultrasound condition are achieved as the optimized reaction conditions are applied focused and uniform to the cellulose matter.
With Hielscher’s ultrasonic bench-top devices such as the UIP1000hdT, UIP2000hdT or UIP4000hdT, several kilogram of nanocellulose can easily produced per day. The full industrial units such as the UIP10000 and UIP16000 handle very large mass streams and allow for the full commercial production of high production volumes. As all of Hielscher’s bench-top and industrial ultrasonicators can be installed as clusters, there is virtually no limit to the ultrasonic process capacity.

Ultrasonic Processing: Hielscher guides you from feasibility and optimization to commercial production!