Autor(es): Ribeiro, Rui ; Guerreiro, Miguel ; Reis, Renato ; Martins, Joana T. ; Vieira, J.M.P. ; Silva, Mariana Martins da ; Covas, J. A. ; Paiva, Maria C.
Data: 2025
Identificador Persistente: https://hdl.handle.net/1822/97923
Origem: RepositóriUM - Universidade do Minho
Assunto(s): Lignin; Lignin-based fibers; PET-G; PC/ABS; Thermal stabilization; Carbon fibre precursor
The growing environmental awareness, the search for alternatives to fossil resources, and the goal of achieving a circular economy have all contributed to the increasing valorization of biowaste to produce bio-based polymers and other high-value products. Among the various biowaste materials, lignin has gained significant attention due to its high aromatic carbon content, low cost, and abundance. Lignin is predominantly sourced as a byproduct from the paper industry, available in large quantities from hardwood and softwood, with variations in chemical structure and susceptibility to hydrolysis. This study focuses on softwood lignin obtained through the LignoForce technology, comparing the thermal and chemical characteristics, and stability, of a recently produced batch with that of a batch that has been stored for four years. Additionally, the development of lignin-based thermoplastic polymer mixtures using Polyethylene Terephthalate Glycol (PET-G) and a blend of Polycarbonate and Acrylonitrile-Butadiene-Styrene (PC/ABS) with high lignin content (5060 wt%) is explored, as well as the production of filaments for carbon fiber production. For this purpose, following melt mixing, the lignin-based mixtures were spun into filaments, which were subsequently subjected to thermal stabilization in an oxidative atmosphere. The lignin phase was well distributed in the PET-G matrix and the two materials presented a good interface, which further improved after thermal treatment under an oxidative atmosphere. After thermal treatment an increase in tensile modulus, tensile strength, and elongation at break of approximately 160%, 200%, and 100%, respectively, was observed, confirming the good interface established, and consistent with structural changes such as cross-linking. Conversely, the PC/ABS blend did not form a good interface with the lignin domains after melt mixing. Although the interactions improved after thermal treatment, the tensile strength and elongation at break decreased by approximately 30%, while the modulus increased by approximately 20%. Overall, the good processability of the lignin/polymer mixtures into filaments, and their physical, chemical, and mechanical characterization before and after thermal oxidation are good indicators of the potential as precursors for carbon fiber production.
