Bonding properties of epoxy resin containing mesogenic group

A liquid crystalline epoxy resin with a mesogenic group was synthesized and its adhesive bonding properties are compared to that of the bisphenol-A type epoxy resin. The bonding strength of the former resin system was higher than that of the latter. This suggested that the high bonding strength of the liquid crystalline epoxy system was due to the large deformation of this system along the stress direction. Bonding strength of all the cured systems had a maximum peak during curing, due to the increase in the internal stress which occurred during the curing shrinkage of the epoxy resins. To decrease the internal stress, we cured the epoxy resin with an excess amount of curing agents. Bonding strength of the system with the added excess amount of curing agent showed a higher value than that for the system with an equivalent amount of curing agent. It was considered that the high bonding strength of the former system was due to the low internal stress in this system.