Ramie Elementary Fiber-Reinforced Chitosan Composite Films: Mechanical Properties and Structural Characterization

Chitosan films have attracted increasing attention as biodegradable packaging materials; however, their relatively low stiffness and limited mechanical stability restrict their practical application. In this study, ramie elementary fiber-reinforced chitosan composite films were prepared using ramie elementary fiber suspensions at concentrations of 0, 0.5, 1.0, and 1.5 g/L. The mechanical properties, chemical interactions, crystalline structure, and surface morphology of the composite films were systematically investigated by tensile testing, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The results showed that the incorporation of ramie elementary fibers significantly affected the mechanical behavior of chitosan films. Among the tested concentrations, the composite film with 0.5 g/L ramie elementary fibers exhibited the best overall performance, with the elastic modulus increasing by 130% from 67.46 MPa to 155.14 MPa compared with the pure chitosan film. FTIR analysis indicated that the formation of hydrogen-bonding between ramie elementary fibers and the chitosan matrix, while XRD results showed that the incorporation of ramie elementary fibers enhanced the structural ordering of the chitosan-based composite films without forming a new crystalline phase. SEM observations further confirmed that an appropriate fiber content promoted uniform dispersion and good interfacial bonding, whereas excessive fiber addition led to aggregation, surface roughening, and interfacial defects. These findings demonstrate that low-content ramie elementary fibers can effectively improve the stiffness and structural stability of chitosan composite films, providing a potential strategy for developing biodegradable fiber-reinforced packaging materials.