Research Progress in Chitin/Chitosan-Based Biomass Adhesives: Extraction Processes, Composite and Chemical Modification.

Traditional fossil-based adhesives, hindered by issues such as formaldehyde emission, dependence on fossil resources, and poor biodegradability, struggle to meet the global demand for low-carbon green development. Biomass-based adhesives have thus emerged as a core alternative. Among them, chitin/chitosan derived from biomass waste such as shrimp and crab shells demonstrates significant potential in the adhesive field due to its renewability, controllable structure, biocompatibility, and inherent antibacterial properties. However, mainstream biomass adhesives like soy protein and starch adhesives suffer from poor water resistance and insufficient wet adhesion strength. Pure chitin/chitosan-based adhesive systems also exhibit low wet strength retention. Furthermore, the overall development faces challenges including high extraction costs, insufficient performance synergy, poor industrial compatibility, and a lack of standardized systems. This review follows the framework of "resource-extraction-modification-performance-application-challenges" to systematically summarize relevant research progress. It clarifies the molecular structure and intrinsic advantages of chitin/chitosan, outlines extraction processes such as acid/alkali and enzymatic methods, and characterization techniques including FT-IR and XRD. The review focuses on analyzing modification strategies such as composite modification, chemical modification, biomineralization, and biomimetic design, and verifies the application potential of these adhesives in wood processing, biomedicine, paper-based packaging, and other fields. Research indicates that chitin/chitosan-based adhesives provide an effective pathway for the green transformation of the adhesive industry. Future efforts should concentrate on developing green extraction processes, designing multifunctional integrated systems, and achieving full resource utilization of biomass. Additionally, establishing comprehensive standardized systems and promoting the translation of laboratory research into industrial applications are crucial to driving the industry's green transition.