Material Applications of Lignin

Recently, lignin has extensively been investigated for its material applications such as biocomposites, hydrogels, surfactants, and other materials. Owing to its aromatic nature, three-dimensional network structures, and abundance of functional groups, lignin is beneficial for replacing petroleum resources and is compatible with other commercial resins, expanding its applications. However, the applications of lignin-based materials are still at an early stage compared to cellulose-based materials due to the inherent molecular complexity and heterogeneity of lignin with technical challenges in its processing. This chapter introduces recent progress in lignin-based composites and hydrogels among various approaches. To better understand lignin-based materials, the impacts of lignin species, contents, synthesis/fabrication methods, and other co-components on the technical performance and characteristics of the lignin-based composites and hydrogels in recent studies are reviewed. In composite applications, lignin can enhance thermal, chemical, and dimensional stability, as well as biodegradability, UV blocking, antioxidant property, and antimicrobial activity. Similarly, lignin-based hydrogels demonstrate excellent biocompatibility with antibacterial and antioxidant properties. Current challenges and future perspectives of lignin-based materials are also discussed in this chapter.