Explanation
Also known as outlet expansion and die swell, it refers to the phenomenon that when macromolecule melt is forced to extrude out of the die, its diameter expands, the size of the extrudate is larger than the die size, and the cross section shape also changes. It is a typical manifestation of viscoelasticity unique to macromolecule melt. The macromolecule chain with random linear clusters has orientation at the entrance of the die due to the population effect. This orientation is not fully relaxed in the flow fields or flow channels of the die, so after leaving the die and losing the constraint, the elasticity recovery of the macromolecule chain occurs, which leads to the increase of the size of the extrudate and the change of the cross section shape.
Classification
No classification at present.