A Review on the Lignin Biopolymer and Its Integration in the Elaboration of Sustainable Materials

• Main Authors: Francisco Vásquez-Garay, Isabel Carrillo-Varela, Claudia Vidal, Pablo Reyes-Contreras, Mirko Faccini, Regis Teixeira Mendonça
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Sustainability
• Subjects: lignin; pulping processes; lignin valorization; biocomposites; sustainable materials; biomaterials
• Online Access: https://www.mdpi.com/2071-1050/13/5/2697

Lignin is one of the wood and plant cell wall components that is available in large quantities in nature. Its polyphenolic chemical structure has been of interest for valorization and industrial application studies. Lignin can be obtained from wood by various delignification chemical processes, which give it a structure and specific properties that will depend on the plant species. Due to the versatility and chemical diversity of lignin, the chemical industry has focused on its use as a viable alternative of renewable raw material for the synthesis of new and sustainable biomaterials. However, its structure is complex and difficult to characterize, presenting some obstacles to be integrated into mixtures for the development of polymers, fibers, and other materials. The objective of this review is to present a background of the structure, biosynthesis, and the main mechanisms of lignin recovery from chemical processes (sulfite and kraft) and sulfur-free processes (organosolv) and describe the different forms of integration of this biopolymer in the synthesis of sustainable materials. Among these applications are phenolic adhesive resins, formaldehyde-free resins, epoxy resins, polyurethane foams, carbon fibers, hydrogels, and 3D printed composites.