Design and characterization of high‐performance epoxy adhesive with block copolymer and alumina nanoparticles in aluminum‐aluminum bonded joints: Mechanical properties, lap shear strength, and thermal stability

Abstract

AbstractIn this research, phenolic resin and poly (butyl‐acrylate‐block‐styrene) copolymer were used in the formulation of epoxy adhesive to improve its thermal stability and toughness. Also, in order to improve the mechanical properties such as the modulus and tensile strength, aluminum oxide nanoparticles (NPs) were added to the epoxy based resin. Effects of different factors such as percent contents of phenolic resin, toughening agent, and aluminum oxide NPs on the microstructure, mechanical properties, and thermal stability of the epoxy‐based adhesives were investigated. Thermogravimetric analysis, Fourier transform infrared spectroscopy, and field‐emission scanning electron microscopy were used to investigate the thermal, mechanical, and morphological properties of the prepared epoxy adhesive samples. In addition, the curing kinetics of the optimal specimens was studied based on differential scanning calorimetry (DSC). The experimental results indicated that the phenolic decreased strength of dog‐bone samples, while increased the adhesion strength in metal‐to‐metal single‐lap strength. On the other hand, addition of block‐copolymers as toughening agent led to a consistent decrease in the modulus as well as increasing the tensile strength. Also, results of single‐lap strength tests showed that, in the optimal quad system, the four components exhibit synergetic effects and show a single‐lap strength that is 152% higher than that of pure epoxy. The DSC analysis indicated that the presence of alumina NPs and block‐copolymers tend to reduce the initial curing temperature while increasing the curing reaction heat.