تهيه و بررسي خواص فيزيكي و مكانيكي چسب‌هاي پايه اپوكسي حاوي چقرمه‌كننده هسته-پوسته آكريلاتي و نانو ذرات اكسيدتيتانيوم

Preparation an‎d investigation of physical an‎d mechanical properties of epoxy-based adhesives containing acrylate core-shell toughening an‎d titanium oxide nanoparticles

مهندسي شيمي

In the present study, a core–shell toughening agent (with a butyl acrylate core an‎d a methyl methacrylate shell) along with titanium dioxide nanoparticles was employed to enhance the mechanical an‎d thermal properties of the final epoxy-based adhesive. With the aim of improving the performance of epoxy adhesives, the effect of titanium dioxide nanoparticles surface-modified by layered double hydroxides (LDHs) was investigated at loadings of 1, 2, an‎d 5 phr. The success of the surface modification was eva‎luated through Fourier Transform Infrared Spectroscopy (FTIR), while Energy Dispersive X-ray Spectroscopy (EDX) an‎d Ultraviolet–Visible (UV–Vis) spectroscopy were applied to confirm the presence of LDH constituent elements on the nanoparticle surface an‎d to further support the FTIR findings. In addition, X-ray Diffraction (XRD) analysis was conducted to examine crystalline characteristics an‎d interlayer spacing, an‎d the results revealed that surface modification led to the appearance of diffraction peaks at lower angles, indicating increased crystallinity an‎d enlarged interplanar distances, which ultimately improved interfacial bonding an‎d enhanced mechanical an‎d thermal properties. To investigate the toughening mechanisms an‎d the dispersion of both the toughening agent an‎d titanium dioxide nanoparticles within the epoxy matrix, the fracture surfaces of optimized dumbbell-shaped specimens were examined using Field Emission Scanning Electron Microscopy (FESEM), revealing mechanisms such as cavitation, crack deflection, an‎d crack blunting that contribute to effective stress distribution an‎d improved crack resistance. The experimental results demonstrated that incorporation of 10 phr phenolic modifier, 2.5 phr core–shell particles, an‎d 2 phr titanium dioxide nanoparticles, particularly those surface-modified with LDHs, significantly improved the physical an‎d mechanical properties compared to neat epoxy resin. Among the formulations, the sample containing 2 phr surface-modified TiO₂ nanoparticles together with 2.5 phr core–shell toughener exhibited the highest synergistic effect an‎d achieved maximum lap shear strength, tensile strength, modulus, an‎d toughness relative to pure epoxy, with increases of 320%, 192%, 18%, an‎d 1050%, respectively. Thermogravimetric analysis (TGA) results indicated that the onset decomposition temperature increased from 176°C to 209°C, representing a 33°C improvement compared to neat epoxy, while the char residue increased by 40%. Ultimately, the presence of core–shell particles an‎d surface-modified nanoparticles intensified interfacial interactions an‎d created a stronger interface with the epoxy matrix, an‎d due to the high stability of the inorganic layers, restricted chain mobility, an‎d delayed oxidation of the epoxy matrix, thermal stability was significantly enhanced. Rheological results further revealed that the combined incorporation of surface-modified TiO₂ nanoparticles an‎d the core–shell toughener increased crosslink density an‎d strong interactions, resulting in a more developed network structure compared to neat epoxy, while the gel point decreased from 98°C to 89.8°C, confirming an accelerated curing reaction an‎d faster formation of crosslinked regions.

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