Water - nanocellulose interactions and optimization

Abstract

The purpose of this Master's thesis was to study the interactions of water and cellulose nanoparticles. The aim of the theoretical part of the thesis was to provide an interdisciplinary understanding basis for water -nanocellulose interactions. In the experimental part the findings of the theoretical part were used to develop and validate informative, scalable, and convenient characterization procedures of nanocelluloses in aqueous suspensions.

As a result of the theoretical part, two different grades of nanocellulose were developed. These nanocellulose grades were able to re-disperse in water after drying, still maintaining the material properties. In the experimental part, the particle size of nanocellulose in water correlated with viscosity at different shear-rates. Further on, the viscosity differences of the dried nanocelluloses and the reference were small. The same type of viscosity fluctuations was also observed for other samples. Also, transmittance measurements showed significant particle size dependence and in addition stable measurement values. The transmittance percentage difference for nanocelluloses of known particle size ranges was 36.82 % at 850 nm, while the corresponding value for the dried and re-dispersed nanocellulose grades were -0.07 % and 2.40 % compared to the reference. Scanning electron microscopy images and pulp -nanocellulose composite characterizations confirmed the findings of the viscosity and transmittance measurements.

As a conclusion of the theoretical part, it can be confirmed that the studied area is of absolute importance for water -nanocellulose processes and applications such as drying and redispersion. The objective of the experimental part was also accomplished. Viscosity and especially transmittance measurements were sensitive to the particle size of nanocellulose. Further on, they were convenient and stable measurements, in particular transmittance.