Structurally tuned PLA chitosan composites through cryogenic mechanochemistry for biofunctional material development

Abstract Polylactic acid or PLA based biocomposites can increasingly serve as alternatives which are eco-friendly to polymers derived from petroleum. However, inadequate filler dispersion along with poor interfacial adhesion limit the structural and functional performance of customary PLA-natural fiber systems. In this study, we have developed a new class of multiscale PLA composites with micro-chitin fibers (MCFs) and also chitosan nanowhiskers (CSWs) when we did process them through cryogenic ball milling and then we molded them with compression. This method, by greatly improving interfacial integration at both micro and nano levels and also harnessing synergistic advantages of hierarchical chitin reinforcement and also low-temperature mechanochemical dispersion, enables solvent-free, scalable fabrication of a novel processing-materials combination that was not explored in prior biocomposite systems. Composites with 5 wt% CSW showed outstanding improvements because flexural strength and modulus increased around ~ 38% and ~ 42%, and storage modulus (E′) rose around ~ 48% because elastic response improved. Thermal analysis revealed T₁₀, T₅₀, and Tder shifts up to 26 °C along with char yield nearly doubled (11.3%). These results indicated an improvement with thermal stability. FTIR-PAS and SEM analyses revealed that the bonding was stronger, in that interfacial integrity was increased. Around 40% reduction of void was attained, also 2× higher fiber–matrix contact area was attained. CSW optimized crystallization then damping behavior induced nucleation plus interfacial stiffening. With their strength now combined, with their barrier now functioning, and with their bioactivity now working, these materials can potentially apply strongly for biomedical scaffolds, for eco-packaging, and for structural components that compost, while aligning fully with goals for sustainability and for circular economy.