A new di®erential equation for polymer melts: The enhanced Pom-Pom model

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A new molecular constitutive equation for a class of branchedpolymers has been introduced by McLeish and Larson(J.Rheol. 42(1), 1998), the Pom-Pom model. Incorporating aGiesekus type of oriental diffusion in their differential form(which predicts zero $N_2$) and writing it in a closeddifferential form for the stress tensor, results in a generalizeddifferential constitutive equation. The non-linear parameterrelated to the Giesekus part of the model accounts for a secondnormal stress difference. Linear parameters are fitted to datafrom dynamic measurements, and most of the non-linear parametersto the transient uniaxial elongational data. It is demonstratedfor different polymers that with this Extended Pom-Pom model(EPP) a very good quantitative agreement can be obtained over a wide range of well defined rheometric experiments. This is exceptional and, in our opinion, shows that the Pom-Pom model is a majot step forwards in the field of viscoelastic constitutive equations.
Original languageEnglish
Title of host publicationProc. 2nd Workshop on Inverse problems in rheology and related experimental techniques
Place of PublicationGermany, Badenweiler
Publication statusPublished - 2001


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