Extruder with dual flighted extrusion screw

A screw extruder adapted to convey thermoplastic materials from inlet to outlet in separate streams comprising a screw body rotatable within a barrel defining a cylindrical chamber having an inner wall, a feed inlet at one end of said chamber and a shaping die on the other end thereof, said screw body having a plurality of different, parallel flights on its outer surface providing a plurality of different parallel channels or passageways between the outer surface of the screw body and the inner wall of the barrel throughout substantially the axial extent of said chamber from said inlet to said die to prevent any mixing of the materials, and a plurality of separate feed hoppers connected to said feed inlet adapted to feed thermoplastic materials separately to the plurality of different parallel channels or passageways simultaneously.