A twin screw extruder to conduct reactive extrusion such as graft-polymerization and polymer blending is used for the creation of newly functionalized polymers/polymer blends with very sophisticated morphology. Recent morphology control is aimed at the level of nano-scale. A twin screw extruder is the most preferred device for these purposes, but must be solved various issues on the control of optimum residence time, polymer temperature, melting and mixing. This study deals with various extrusion behavior related to molten polymer temperature, residence time, intensity of mixing, dispersive melting and devolatilization in reactive extrusion processes. Furthermore, it is also discussed that the combination of polymer blends and inorganic nano-fillers can be utilized to obtain finer morphology in polymer blending just like a compatibilizer.