Technology of lignin modification: progress in specialty and green adhesives’ mechanical properties

Abstract

Lignin, a natural polymer, is considered an ideal choice for adhesive production due to its abundant resources, renewability and unique chemical structure. Lignin has gained widespread use in specialty and green adhesives in key industries such as construction, medicine, aerospace, and smart electronics. However, its performance in adhesive formulations is limited by low viscosity, reduced cross-linking capacity, and poor compatibility. To address these challenges, researchers have explored various modification techniques, improving lignin's cross-linking potential and adhesion properties. These enhancements are achieved by increasing the number of active functional groups and employing both physical and chemical modification methods. This article provides a comprehensive review of the application of lignin modification technologies in specialty and green adhesives. It systematically outlines various modification processes, including physical methods such as microwave and ultrasonic depolymerization, as well as chemical methods such as demethylation, hydroxymethylation, and phenolization, while offering an in-depth analysis of the advantages and disadvantages of each technique. Finally, the article discusses future prospects for enhancing lignin-based adhesives through interdisciplinary collaborative innovations and breakthroughs in advanced technologies, with the goal of expanding their high-end applications in the realms of green and specialty adhesives, thus contributing to the industry's sustainable development.