Search Results (3)

Reinforced concrete structures are prone to the development of microcracks during service. In this study, a composite-modified epoxy potting adhesive was formulated using nano-TiO₂, carboxyl-terminated butadiene nitrile liquid rubber (CTBN), and the reactive diluent D-669. The mechanical properties and effectiveness of this composite adhesive in repairing oblique cracks were systematically evaluated and compared with those of single-component-modified epoxy adhesives. Key material parameters influencing the performance of oblique crack repair were identified, and the underlying repair mechanisms were analyzed. Based on these findings, a theoretical formula for calculating the shear-bearing capacity of beams with repaired web reinforcement was proposed. Experimental results demonstrated that compared to single-component-modified epoxy resin, the optimally formulated composite adhesive improved the tensile strength, elongation at break, and bond strength by 4.07–21.16 MPa, 13.28–20.4%, and 1.05–3.79 MPa, respectively, while reducing the viscosity by 48–872 mPa·s. The viscosity of the adhesive was found to play a critical role in determining the repair effectiveness, with toughness enhancing the crack resistance and bond strength contributing to the structural stiffness recovery. The adhesive effectively penetrated the steel–concrete interface, forming a continuous bonding layer that improved energy dissipation and significantly enhanced the load-bearing capacity of the repaired beams. Full article

Epoxy composite materials are widely used in power equipment. As the voltage level increases, the requirement of material properties, including electrical, thermal, and mechanical, has also increased. Introducing thermally conductive nanofiller to the epoxy/liquid rubber composites system is an effective approach to improve heat performance, but the effects of thermally conductive nanofillers on relaxation characteristics remain unclarified. In this paper, nano-alumina (nano-Al₂O₃) and nano-boron nitride (nano-BN) have been employed to modify the epoxy/carboxyl-terminated liquid nitrile–butadiene rubber (epoxy/CTBN) composites system. The thermal conductivity and glass transition temperature of different formula systems have been measured. The effect of the nanofillers on the relaxation behaviors of the resin matrix has been investigated. Results show that the different kinds of nanofillers will introduce different relaxation processes into the matrix and increase the conductivity at the same time. This study can provide a theoretical basis for the synergistic improvement of multiple properties of epoxy resin composites. Full article

Filled high thermal conductivity epoxy composite solves the problem of the low thermal conductivity of the epoxy resin itself, but the addition of the thermal conductive filler reduces the mechanical properties of the composite, which limits its application in the field of high voltage insulation. In this work, carboxyl-terminated butadiene nitrile liquid rubber (CTBN) was used to toughen the boron nitride-epoxy hybrid system, and the effects of different contents of CTBN on the mechanical properties, thermal conductivity, glass transition temperature, thermal stability, and dielectric properties of the composites were investigated. The results showed that when the content of CTBN was 5–15 wt.%, the CTBN formed a dispersed island structure in the epoxy resin matrix. The toughness of the composite increased by about 32%, the breakdown strength was improved, and the thermal conductivity was about 160% higher than that of pure epoxy resin. As the CTBN content increased, the glass transition temperature and thermal stability of the composite decreased and the dielectric constant and the dielectric loss increased. When the CTBN content is 10–15 wt.%, a toughened epoxy composite material with better comprehensive properties is obtained. Full article