Lignin Esters and Their Composites with PLA

Abstract

Due to depleting resources for fuel and chemical production, new sustainable and renewable materials are needed. A potential material for this is lignin, which has been of interest for the past decades. Lignin is a complex bio-based polymer extracted from plant biomass during processes such as pulping in the paper and pulp industry. But the faith of lignin has for a long time been burning for energy. Lignin has a high potential to be used in value-added products, including biofuels, adhesives, and bioplastics. Furthermore, lignin-derived compounds hold promise in the development of renewable chemicals and materials, contributing to a sustainable future. Lignin can be challenging to use on its own, therefore it has been implemented e.g., in composites together with other bioplastics. To enhance the compatibility of lignin and the other bioplastic in a composite, chemical modification of the lignin can be done. In this thesis spruce alkaline lignin has been esterified with five different acyl chlorides, resulting in five different lignin esters with varying lengths of grafted carbon chains. These modified lignins were blended with PLA to form PLA/Lignin composites. The thermal, mechanical, and rheological properties of the composites were analyzed. The aim was to look into how the different modifications affect the properties of the composites. Lastly the materials were tested in 3D printing. Based on the results from the analyses and 3D printing, the most promising materials for 3D printing were determined.