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Dynamic melt rheology. II: Re‐examining the relationship of g ′ in oscillatory rheometry to the melt elasticity
Author(s) -
Khanna Y. P.,
Slusarz K. R.
Publication year - 1993
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760330211
Subject(s) - rheometry , rheology , die swell , elasticity (physics) , materials science , viscoelasticity , composite material , elastic modulus , talc , polymer , stiffening , drop (telecommunication) , dynamic mechanical analysis , stiffness , polypropylene , plastics extrusion , mechanical engineering , engineering
In oscillatory rheometry, since the dynamic storage modulus ( G ′) represents the elastic component of the viscoelastic melt, it has been a rather common practice to associate it with the melt elasticity. Although this assumption might be valid in many instances, there can be exceptions as well. In the present study, we have chosen polypropylene/talc system to demonstrate an exception. For example, the melt elasticity decreases with increasing talc content as revealed by extrudate die swell, entrance pressure drop, and elastic compliance measurements; the opposite trend being reflected by G ′. We can envision similar exceptions when stiffening agents are added to a polymer melt, e.g., rigid rod molecules. We are suggesting that G ′ represents the elastic modulus or stiffness of the melt, which in certain situations might not reflect elasticity, i.e., the ability of a melt to recover from a deformation. The implication of the present manuscript is that caution be exercised when relating G ′ to the melt elasticity of a polymer.