A liquid crystalline thermosetting-epoxy-based composite was fabricated using diglycidyl ether of 4,4'-biphenol, boron nitride as the filler, and sulfanilamide as the curing agent. To investigate the thermal behavior, thermogravimetric analysis was performed, and temperature differences of the sample were recorded when using 1.0-7.0 wt.% boron nitride. The activation energy for thermal decomposition was calculated using the Kissinger method and Flynn-wall method. The results showed that the activation energy was proportional to the amount of added filler.