Extrudate shrinkage control and reduction.

摘要

An extrusion apparatus (10) for extruding visco-elastic materials includes an extruder head (12) for preliminary shaping of a visco-elastic melt and a splice bar die assembly for final shaping of the visco-elastic melt. Both the extruder head (12) and the die assembly have flow channels that include low elongational flow zones where elongational flow is reduced and controlled, thereby reducing and controlling the resulting shrinkage of the extrudate (24). Extrudate shrinkage can also be reduced and controlled by controlling the die swell of the visco-elastic melt by rotating the roller (20) at a selected roller speed less than the melt speed.