Enhanced mechanical properties and higher UV resistance of epoxy nanocomposites using TiO2@SiO2@APTES nanoparticles

Abstract

Titanium dioxide (TiO2) is known for its excellent UV-shielding capability, but its inherent photocatalytic activity poses a problem by degrading the polymer matrix and compromising durability. To address this issue, this study involved creating a physical barrier by forming a silica (SiO2) shell on the TiO2 surface via a sol-gel process, followed by surface functionalization with (3-aminopropyl)triethoxysilane (APTES) to maximize interfacial bonding with the epoxy. XPS and TEM analyses confirmed the intended core-shell structure and the introduction of amine groups, while photocatalytic experiments demonstrated that the SiO2 shell effectively suppressed the photoactivity of TiO2. In mechanical property evaluations, the addition of pristine TiO2 resulted in a 15.8% improvement in flexural strength, whereas TiO2@SiO2 showed a slightly lower improvement of 13.2%. However, the composite with TiO2@SiO2@APTES exhibited a maximum flexural strength improvement of 26.1% and retained over 52% higher strength than pure epoxy even after 15 days of UV accelerated aging. This clearly demonstrates that amine functionalization not only protects the epoxy matrix from UV degradation but also provides superior mechanical reinforcement through strong interfacial bonding. Therefore, this study presents an effective strategy for designing highly durable composite materials for extreme environments, such as aerospace applications.