Chitin nanowhiskers: a review of manufacturing, processing, and the influence of content on composite reinforcement and property enhancement†

This review critically examines the potential of chitin nanowhiskers (ChNWs) as high-performance reinforcement materials for the plastics industry, with a specific emphasis on their impact on composite properties. It provides a structured overview of established ChNW preparation techniques—acid hydrolysis, oxidation, mechanical disintegration, and green solvent processing—and discusses advanced fabrication strategies for producing ChNW-reinforced composites of both natural (e.g., cellulose, chitosan, starch, hyaluronan) and synthetic (e.g., polyvinyl alcohol, poly(α-cyanoacrylate), polyaniline, polyethylene terephthalate, polypropylene) types. Key performance enhancements include increased mechanical strength, tensile strength, Young's modulus, thermal stability, and water resistance. These enhancements make ChNW-based composites suitable for real-world applications in aerospace, biomedical devices, packaging, and construction. Unlike previous reviews that emphasize only processing methods, this work identifies and highlights structure–property relationships as a central theme, bridging nanoscale morphology with macroscopic functionality.