Chitin-based fillers for thermoplastic composites: A critical review of processing, properties, and performance

This review examines the potential of chitin as a filler in polymer science and its applications in the plastics industry. Particular attention is given to recent developments in the production of chitin fibers, crystals, and whiskers, as well as their surface modification and use as reinforcing agents in thermoplastic composites. Chitin is the second most abundant polysaccharide after cellulose and can be extracted from crustacean waste, providing a cost-effective and environmentally friendly source of this valuable biopolymer. Chemical modification of chitin can improve dispersibility, hydrophobicity, and interfacial compatibility with polymer matrices, thereby expanding its potential applications. Incorporating chitin-based fillers into thermoplastic polymers offers opportunities to reduce dependence on fossil-derived materials while enabling the use of low-cost fillers in commodity plastics. Despite this potential, chitin has received comparatively limited attention as a filler material. This review examines potential reasons for this gap and evaluates current strategies to address existing limitations from a chemical and materials perspective. Methods for producing chitin fillers are critically assessed, highlighting their advantages and limitations. Finally, the relationship between chitin structure, filler performance, and economic potential is analyzed, with particular relevance to biodegradable packaging, agricultural mulch films, and lightweight structural materials.