The invention at hand relates to a rotor disk (1) to be inserted into a receptacle (2) for the treatment of polymers, having a disk body (3) on whose top side (4) mixing and/or comminuting tools (5) are providable and on whose opposite underside (6) a number of conveying ribs (7) extending from the interior to the exterior are provided with which during operation polymer particles are transportable towards the exterior or, respectively, that during operation exert a force directed from the center (8) of the rotor disk (1) towards the exterior on the polymer particles grasped by the conveying ribs (7). In accordance with the invention it is provided that the conveying ribs (7) are curved concavely in the direction of rotation or, respectively, of movement.