The effect of the composition of an epoxy blend based on a cycloaliphatic (CAE) and diglycidyl ether of bisphenol A (DGEBA) epoxides containing N-benzylpyrazinium hexafluoroantimonate (BPH) as a thermal or UV latent initiator was investigated in the context of their thermal stability and mechanical properties. The compositions of a CAE-DGEBA blend were varied within 100:0, 80:20, 60:40, 20:80, and 0:100 by mole percent. Latent properties were measured by the degree of conversion. As a result, the thermal stability characterized from the initial decomposition temperature (IDT), the temperature of maximum weight loss (T-max), the integral procedural decomposition temperature (IPDT), and the decomposition activation energies by TGA increased when the DGEBA composition was increased. According to the mechanical measurements, the flexural and tensile strengths increased with an increase of the DGEBA composition because of the compact hydrogen bond, long repeat unit, and bulky side groups of the DGEBA, while both the elastic and tensile moduli decreased. This latter result was attributed to the DGEBA intermolecular interaction, resulting in a toughened three-dimensional network, which dispersed the internal stress.