Blended lignin as a precursor for carbon-based materials, development and applications

The development of high value technologies from waste resources is critical to tackle the depletion of natural resources. Lignin is a renewable, low cost by-product of paper industry. Its unique aromatic structure is key to a sustainable production of carbon fibres and carbon nanofibres. These materials have applications in high value industries such as aerospace, automotive and leisure as well as energy storage and production, water treatment systems and biosensing. This present thesis investigates the relationship between the lignin chemical structure and its processing properties, both alone and in a polymer blend. Two hardwood lignins are investigated, an as-received organosolv and a hydroxy propylated kraft lignin. The effect of melt extrusion is studied in detail with regards to the chemical modifications sustained by both lignin during processing. A successful blend was developed with thermoplastic poly(urethane) (TPU) that showed strong compatibility and thermal behaviour. The influence of modifications of the lignin chemical structure prior to extrusion was studied in details, to improve the blendability of lignin with bio-based poly(ethylene terephthalate) and optimise the carbon phase of the obtained carbon fibres. A crosslinker was added to the lignin-TPU blend to improve the efficiency of the thermostabilisation phase with regards to crosslinking behaviour and carbon yield. Sustainable lignin-based carbon nanofibres were used to develop a enzymatic glucose sensor. The porosity of the lignin-PLA-based carbon nanofibres was critical to the immobilisation of glucose oxidase for sensing.