Tia Lohtander-Piispa: Functional materials from cellulose and biocolorants

Abstract:

Cellulose, an abundant and renewable material, that can be utilized as a nanomaterial as well as macroscopic fibers has obtained great attention for creating biomaterials for various applications. And color, an everyday phenomenon, is an essential part of almost any kind of material due to its symbolic and cultural meanings. The coloration of cellulosic and other materials is nowadays achieved mainly with synthetized dyes and pigments whose use has been identified especially as a source of aquatic pollution. The renewable biocolorants derived from natural sources are an interesting alternative to synthetic colorants.

The objective of this thesis was to investigate the functional materials made of cellulosics and biocolorants. Two different colorants from forest industry residues (willow bark extract and kraft lignin), high added-value crop Isatis tinctoria (indigo), and fast-growing microalgae Chlorella vulgaris were utilized as colorants for various cellulosic materials from cellulose nanofibrils (CNF), to microcrystalline cellulose, and macroscopic textile fibers. Unlike synthetized colorants, the biocolorants often are mixtures of multiple compounds and exhibit bioactive properties that can be incorporated into cellulosics to create added-value materials. The antioxidant and ultraviolet protecting properties were utilized to create biocomposite films useful for packaging applications. The antioxidant activity and CNF as a carrier matrix were utilized for developing the indigo dyeing towards a more facile process with fewer process steps. In the conventional dyeing process again, the multicomponent structure of biocolorants was found to be a significant feature since they all contribute to the interaction with dyeable cellulose material, dye fixation yield, and the overall result. The foamability and stability of lightweight foams from surfactant, cellulosics, and biocolorants were explored for creating camouflage foams with thermal and spectral stealth properties.

This thesis provides insights into the chemical and physical characteristics of biocolorants, understanding of the multicomponent nature and its effect on coloration, and introduces the potential practical applications for functional materials composed of cellulose and biocolorants.

Follow the remote defence: Zoom

Opponent: Professor Alexander Bismarck, University of Vienna, Austria

Supervisor: Professor Monika Österberg, Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems

Link to electronic thesis: Functional materials from cellulose and biocolorants