The effect of modified silica nanoparticles on the mechanical properties of UV-curable polyurethane acrylate adhesive

In this research, the effect of SiO 2 nanoparticles on the one-component urethane acrylate (UA) based ultraviolet (UV) curing adhesive bonds was studied. UV adhesives attracted attention due to their advantages such as fast curing, being colorless, and thin adhesive layer at the joint. However, one of the drawbacks associated with UV adhesives is their suboptimal mechanical properties. The aim of this work is to fabricate and characterize a nanocomposite adhesive by incorporating silica nanoparticles into the urethane acrylate adhesive. At first, fumed silica nanoparticles were modified by γ-Methacryloxypropyltrimethoxysilane (MPS) and γ-Aminopropyltriethoxysilane (APTES)@methyl acrylate (MA) via sol-gel process and Michael addition reaction then introduced to the urethane acrylate adhesive. A notable betterment was observed within the shear strength of adhesive joints. The morphological and structural characteristics of silica/UA, functionalized silica-MPS/UA, and functionalized silica-APTES@MA/UA nanocomposite adhesives were assessed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The successful dispersion of functionalized silica nanoparticles into the UA adhesive led to the foundation of hardy interfacial adhesion with UA by easing the formation of cross-linking networks between the nanoparticles and UA after UV polymerization that was proved in results. In addition, SEM micrographs show a transition of fracture morphology from smooth to rough surfaces upon the addition of nanoparticles. In addition, an increase in nanoparticle concentration caused a reduction in the contact angle. The shear strength of the 1.5 wt% pristine silica/UA, 1.5 wt% functionalized silica-MPS/UA, and 1 wt% functionalized silica-APTES@MA/UA adhesive composite were 59.37 %, 84.63 %, and 46.51 % increased respectively, as compared to neat UA adhesive.