Synergistically Modified <scp> TiO ₂ </scp> /Epoxy Resin Composites by Organic Dyes and Tannic Acid: Preparation, Mechanical Properties and Enhancement Mechanism

ABSTRACT To improve the brittleness of cured epoxy (EP) resin, organic dyes and tannic acid (TA) are utilized to synergistically modify TiO 2 nanoparticles (NPs) and further to enhance the mechanical properties of TiO 2 /EP composites. Due to methyl orange (MO) and toluidine blue (TB) introducing the active functional groups onto the surface of TiO 2 NPs, it would optimize the dispersity and interfacial strengths of modified TiO 2 /EP composites. For TiO 2 NPs usage of 1 wt%, TA‐TB‐TiO 2 /EP composites exhibit the maximum tensile strength of 54.04 ± 1.54 MPa and flexural strength of 100.05 ± 1.56 MPa, which is approximately 57.78% and 57.41% higher than that of pure EP. After UV radiation for 8 h, the flexural strength of TA‐TB‐TiO 2 /EP composites only decreased about 11.5%, which is much lower than pure EP and modified TiO 2 /EP composites. From the cross‐section morphologies, MO, TB, or TA modified TiO 2 NPs are well contacted and evenly dispersed inside the EP matrix. These modified TiO 2 /EP composites exhibit obvious toughness fracture behavior. Mechanical and UV‐aging properties are compliant with the synergistic enhancement mechanism of MO, TB dyes, and TA in various combinations.