What type of energy is generated when two materials rub against each other?

When two materials rub against each other, the interaction converts kinetic energy from the movement into another form of energy, primarily thermal energy, due to friction. However, mechanical energy is the correct term used to describe the energy associated with the motion and position of an object. Friction, which is a force that opposes motion, leads to a transformation of this mechanical energy into thermal energy as a byproduct of the frictional forces at play.

In contexts involving materials interacting, mechanical energy is key because it's the energy that originates from the physical action of the materials moving against each other. This is essential in understanding how energy changes forms during various processes, including frictional heating.

Although thermal energy is directly related to the effects of this rubbing action, the prompt is specifically asking about the type of energy that is generated in the act of rubbing itself, which is best categorized as mechanical energy initially.