Rheology

Shear viscosity

Biology

Strain hardening exponent

Extensional definition

Paleontology

Composite material

Materials science

Thermoforming

Polypropylene

Extrusion

Layer (electronics)

Extensional viscosity

Hardening (computing)

Tectonics

International Polymer Processing

Many processing operations of polymeric materials are dominated by extensional flow. In this paper the question is addressed in which way rheological data obtained from elongational laboratory experiments can be used to describe the material behavior in various processes. Particularly discussed is the uniformity of geometrical features of items with respect to the strain hardening of the polymeric materials, because uniformity is important for many end-use properties. Convincing correlations with extensional rheology could not be established for thermoforming experiments on polypropylene. However, for blown and drawn films it was found that the uniformity of thickness improved, if strain hardening was introduced. The bubble stability could be related to the melt strength of the sample. Furthermore, the influences of elasticity and strain hardening on the neck-in during drawing of films were elucidated. Moreover, it was shown in which way extensional rheology can be used to assess foaming.

Extensional Rheology and Processing of Polymeric Materials