By means of a novel flow perturbation technique, fundamental details during the extrusion of semi-crystalline and amorphous polymers, such as Polypropyl-ene (PP), Polystyrene (PS), or PP/PS polymer blends can be analyzed with respect to the kinetics of melting and energy input. The effects of extrusion conditions such as throughput and screw speed were examined. A specialized, high-speed data acquisition system, the "Extrusion Pulse Analysis System" (EPAS) has been employed to enable on-line monitoring and data analysis based on an imposed mass disturbance to provide a real-time diagnosis of extrusion melting processes in laboratory and manu-facturing applications. Using the power response profile of the mass perturbation, four key sequential stages of melting have been proposed for twin-screw extrusion of a single component or polymer blends. A "lubricated melting" mechanism is also proposed for the extrusion behaviors of PP/rubber and PS/rubber blends using an Ethylene copolymer and SBS block copolymer as the minor phase ingredient.