A thermal rectifier transmit heat asymmetrically, transmitting heat conductor in one direction and insulating heat in the opposite direction. For conduction at steady state, thermal rectification can occur naturally in systems where the thermal conductivity of the material(s) vary in space and with temperature. However, in virtually all practical applications, rectification will need to be controlled under transient conditions. Using a bulk composite as a model system, we analyze transient rectifying behavior. First, we found that transient rectification can be several times larger than steady state rectification. More specifically, both the thermal diffusivity of the system and temperature-dependent thermal conductivity play an important role in affecting the transient rectifying behavior of the system, with the non-linearity of the system leading to unusual behavior where rectification is maximized.