Constitutive Model Parameters Estimation from Rheotens Steady State and Resonance Characteristics (original) (raw)
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This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Acta Polymerica
The parameters of a generalized rheological model for the description of the flow characteristics of some fluid polymeric systems are determined. Nonlinear regression analysis is used for the fitting of the experimental viscosimetric data. The behaviour of the investigated polymer melts, suspensions and solutions obeys the general equation , where n, σo, μ and m are parameters which characterize the different types of flow behaviour.Die Parameter eines verallgemeinerten rheologischen Modells zur Beschreibung der Fließcharakteristik einiger flüssiger Polymersysteme wurden bestimmt. Die Anpassung der experimentellen viskosimetrischen Meßwerte erfolgte durch nichtlineare Regressionsanalyse. Das Verhalten der untersuchten Polymerschmelzen, -suspensionen und -lösungen folgt der allgemeinen Gleichung , worin n, σo, μ und m Parameter darstellen, die die unterschiedlichen Arten des Fließverhaltens charakterisieren.
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Rheological models for biobased plastics can assist in predicting optimum processing parameters in industrial forming processes for biobased plastics and their composites such as film blowing, or injection stretch-blow molding in the packaging industry. Mathematical descriptions of polymer behavior during these forming processes are challenging, as they involve highly nonlinear, time-, temperature-, and strain-dependent physical deformation processes in the material, and have not been sufficiently tested against experimental data in those regimes. Therefore, the predictive capability of two polymer models, a classical Giesekus and a physically-based Rolie-Poly, is compared here for extensional and shear rheology data obtained on a poly(L-lactide) (PLLA) across a wide range of strain rates of relevance to those forming processes. Generally, elongational and shear melt flow behavior of PLLA was predicted to a satisfactory degree by both models across a wide range of strain rates (for strain rates 0.05-10.0 s −1), within the strain window up to 1.0. Both models show a better predictive capability for smaller strain rates, and no significant differences between their predictions were found. Hence, as the Giesekus model generally needs a smaller number of parameters, this class of models is more attractive when considering their use in computationally demanding forming simulations of biobased thermoplastics.