Hello! everyone
I have some question about die-swell.
We have two HDPE samples which were produced by different catalyst.
They have almost same M.I value and shear viscosity, but are different in die-swell.
I would like to know why they are differerent in die-swell and which factors effects on die-swell difference.
thank you.
Extrudate swell is an elastic response to the deformation of the polymer in the converging zone of the die. As the polymer passes through the converging die it is stretched and elongated. These deformations draw out the molecular structure and extrusion conditions may not provide sufficient time for the molecules to 'relax'. I expect that one of your resins is less linear with more entanglements.
Swell can be reduced or controlled by
These are a few parameters that I recall off the top of my head. You have many interacting parameters to play with.
Good luck!
Ken.
Extrudate (die) swell can be the result of memory of the entrance flow, but it is not required. If you stop the flow for a period longer than the memory of the fluid, and then start it again, you still have the swell. (Reference: A.S. Lodge, in "Rheology of Elastomers", P. Mason and N. Wookey (Eds.) 1958, pp 70-85).
John Aspen Research, -
Opinions expressed herein are my own and may not represent those of my employer.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.