Elongational viscosity and its meaning for the praxis

Processing operations where elongational viscosity and melt strength play an important role include fiber spinning, blow molding and foam 

The meaning of strain hardening and strain thinning is more clearly seen, when the effects of the linear-viscoelastic spectrum of relaxation times and the nonlinear strain measure Q on the elongational viscosity are separated. In the tube model, the strain measure can be represented by the second rank orientation tensor (describing the orientation of tube segments) and a molecular stress function f [6], 

So far, no melt strength data have been reported for branched PP melts. However, from experience with PE melts, it can be expected that melt strength is increased by long-chain branching [8]. 

Meissner, J. (1971) Dehnungsverhalten von Polyathylen-Schmelzen, Rheol. Acta, 10, 230-242. 

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