Die swell

Die swell, also known as extrudate swell, is a common phenomenon in polymer processing. Die swell occurs in instances of polymer extrusion, in which a stream of polymeric material is forced through a die, a specialized tool in manufacturing to shape or cut polymeric materials. Die swell is an instance where a polymer stream is compressed by entrance into a die, and is followed by a partial recovery or “swell” back to the former shape and volume of the polymer after exiting the die, hence the term die swell.