Mechanical performance and aging resistance analysis of zinc oxide-reinforced polyurethane composites

Herein, we report the development of three-dimensional (3D)-printed polyurethane (PU) composite materials reinforced with zinc oxide (ZnO) nanoparticles and stabilised <i>via</i> surface functionalization using the silane coupling agent 3-(trimethoxysilyl)propyl methacrylate (TMSPM). By employing digital light processing (DLP) technology, a series of porous PU scaffolds containing different concentrations of ZnO (0, 1, and 2 wt%) were successfully fabricated. The primary objective was to enhance the mechanical integrity and environmental durability of PU-based components, particularly under ultraviolet (UV) exposure and thermal aging. The inclusion of the TMSPM-modified ZnO nanoparticles significantly improved the homogeneity of the nanoparticle dispersion and the interfacial compatibility between the inorganic fillers and the polymeric matrix. Compared to the control group, ZnO-reinforced scaffolds exhibited up to 53% higher compressive strength and retained over 75% of their mechanical performance after 150 hours of UV and thermal aging. Surface contact angles also increased significantly upon aging, reaching values above 90°, suggesting altered surface morphology and reduced moisture affinity. Additionally, microstructural analysis revealed that ZnO incorporation mitigated the formation of surface cracks and delamination during aging, preserving the structural continuity of the scaffolds. These enhancements are ascribed to the synergistic effects of the ZnO nanofillers, which function as effective UV radiation absorbers and physical barriers that suppress microcrack initiation and propagation within the polymer network. This study demonstrates a viable strategy for improving the long-term performance and structural reliability of 3D-printed PU components by incorporating silane-functionalised ceramic nanofillers. The resulting PU/TMSPM-ZnO nanocomposites are promising for lightweight, mechanically resilient, and aging-resistant applications across a range of sectors, including automotive, aerospace, and outdoor structural engineering.