In this work, an experimental program was performed to determine the influence of clamping pressure on the Izod pendulum impact resistance of several polypropylene homopolymers provided by Repsol-YPF Co. Several sets of tests performed indicate how the uncontrolled application of a clamping pressure may lead to non-consistent results. One of the most influential parameters on the clamping torque sensitivity is temperature. From the results obtained, the following conclusion can be established: the clamping pressure is an influential factor only over the material T g and its effect is related to the material brittleness, diminishing as the temperature comes closer to the brittle–ductile transition temperature.