System and die for forming a continuous filament reinforced structural plastic profile by pultrusion/coextrusion

A system and method are disclosed for producing a continuous filament reinforced thermoplastic profile having consistent cross section. A continuous reinforcing filament is pre-wetted with a first thermoplastic resin and introduced into a die, where it is contacted with a second thermoplastic resin extruded from an extruder at melt state. The temperature of the die is carefully controlled so that the pre-wetted filament and first resin do not cure or solidify until after they have contacted and mixed with the second thermoplastic resin. The mixture temperature is then controlled to make a substantially solidified profile pre-shape. A capping layer comprising a third thermoplastic resin is then coextruded onto the outer surface of the pre-shape. A multistage die for bringing together the filament and thermoplastic resins and for maintaining appropriate temperatures at each stage of the profile-forming process is also disclosed.