Influences of amine/epoxide ratio on cross-linking structure and mechanical properties of cured hydrogenated epoxy resin sheets and single-lap joints

The influence of the amine/epoxide ratio (N–H/Ep.), controlled from 0.5 to 2.0, on the network structure and mechanical properties of cured epoxy resin (CER) was investigated using a cycloaliphatic epoxy and amine components, in a form of sheets and single-lap joints (SLJs). The cross-linking density and glass transition temperature of CER sheet was the highest at 1:1 stoichiometric N–H/Ep. ratio and became lower with being out of the ratio. On the contrary, tensile strength of sheet and shear strength of SLJ monotonically increased and decreased with an increase in amine content, respectively. Excess amine can work as fillers for sheets and made interfacial strength weaken between adherend and adhesive for SLJs. Changing the N–H/Ep. ratio can control the mechanical properties of not only sheets, but SLJs. Comparisons with mechanical properties of sheets and SLJs are quite helpful to design the high-performance adhesive. [Display omitted] •Effect of amine/epoxide ratio on mechanical properties was investigated.•Tensile strength of sheets increased toward the amine-rich direction.•Mechanical properties of single-lap joints are influenced by the interface.•Shear strength of single-lap joints decreased toward the amine-rich direction.