Super-Flexibility and High-Temperature Adhesion of Epoxy Structural Adhesives Endowed by Homogeneous Rigid–Flexible Crosslinking Networks

Epoxy adhesives that combine flexibility, high-temperature adhesion property, and medium–low-temperature curing ability are an urgent need in the microelectronic device era. Unfortunately, it is still a challenge so far. In this context, two kinds of curing agents are combined to construct homogeneous rigid–flexible crosslinking networks via the stepwise curing method for preparing an epoxy adhesive with prominent deformation ability and high-temperature adhesive strength. Detailed analysis showed that the crosslinking network constructed by the stepwise curing method was higher and more homogenous than that of the one-step curing method. Benefitting from the homogeneous rigid–flexible crosslinking network, the elongation at break and high-temperature adhesion strength (200 °C) of the epoxy adhesive prepared by the stepwise method were up to about 100% and 1.60 MPa, respectively, which were about 1677.7 and 112.5% higher than those of the epoxy adhesive cured by the one-step curing method. The epoxy adhesive with medium–low-temperature curing ability, excellent flexibility, and high-temperature adhesion was first reported. It is expected that this work could provide some inspiration to design the special epoxy adhesives.