Toughened Bamboo-Fiber-Modified Epoxy Resin: A Novel Polymer Coating for Superior Interfacial Compatibility

Epoxy resin is regarded as a reliable option for coating advanced materials owing to its outstanding strength, adhesion, and stability. However, its relatively weak toughness compared to common materials has limited its application. In this study, the toughness of epoxy resin was enhanced by incorporating bamboo fibers, and a novel polymer coating material for bamboo-fiber-reinforced epoxy resin was developed. Different fiber pretreatment methods were employed to address the issue of poor interfacial performance between bamboo fibers and epoxy resin, aiming to optimize its performance as an advanced material coating. The effects of curing agents, fiber mesh sizes, fiber contents, and fiber pretreatment methods on the mechanical properties of the fiber-modified resin composites were investigated. The findings indicate that the JH45 and T31 curing agents were more effective in promoting the homogeneous dispersion of fibers within the epoxy resin. Additionally, bamboo fibers modified with KH550 exhibited enhanced interfacial properties: the tensile strength of the composite demonstrated a respective increase of 31.1% and 27.0% compared to untreated fibers. Increasing the mesh size proved advantageous for improving tensile properties, albeit potentially impacting the compressive properties. Particularly noteworthy was the significantly enhanced interfacial compatibility between bamboo fibers treated with the silane coupling agent KH550 and the epoxy resin. Analysis using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) revealed that treating bamboo fibers with sodium hydroxide effectively enhanced bonding at the fiber–resin interface. This enhancement was attributed to the combined effects of bamboo fiber hydrolysis and delamination reactions. The silane coupling agent promoted the chemical reaction between bamboo fibers and epoxy resin through grafting, thereby strengthening the cross-linking property of the composites. These findings offer valuable insights into the design and fabrication of natural-fiber-reinforced polymer composites suitable for coating advanced materials.