Steady states in extensional flow of strain hardening polymer melts and the uncertainties of their determination

2013 ◽  
Vol 57 (4) ◽  
pp. 1065-1077 ◽  
Author(s):  
Helmut Münstedt ◽  
Zdeněk Starý
Keyword(s):  
Strain Hardening ◽  
Polymer Melts ◽  
Extensional Flow ◽  
Steady States

Suspensions of monodisperse spheres in polymer melts: particle size effects in extensional flow

2002 ◽  
Vol 42 (1-2) ◽  
pp. 184-190 ◽  
Author(s):  
Jean-François Le Meins ◽  
Paula Moldenaers ◽  
Jan Mewis
Keyword(s):  
Particle Size ◽  
Size Effects ◽  
Polymer Melts ◽  
Extensional Flow ◽  
Particle Size Effects ◽  
Monodisperse Spheres

Characterisation of an Industrial Polymer Melt Through Either Uniaxial Extension or Exponential Shear Data: An Application of the Pom-Pom Model

2003 ◽  
Vol 13 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Suneel ◽  
Richard S. Graham ◽  
Tom C.B. McLeish
Keyword(s):  
Strain Hardening ◽  
Simple Shear ◽  
Linear Response ◽  
Polymer Melts ◽  
Molecular Model ◽  
Uniaxial Extension ◽  
Polymer Melt ◽  
Non Linear ◽  
Ldpe Melt ◽  
Made In

Abstract We present new non-linear data in extension and two different shear histories. These data are used to compare the effectiveness of using exponential shear data and uniaxial extension data to characterise the non-linear response of an industrial LDPE melt with the pom-pom molecular model. We conclude that extension and exponential shear both allow good predictions to be made in simple shear. However, the characterisation spectrum obtained from exponential shear data fails to predict the correct degree of strain hardening at low extension rates. From this study we are able to suggest circumstances under which exponential shear provides a useful characterisation of branched polymer melts.

scholarly journals Recoverable Extensional Flow of Polymer Melts and Its Relevance for Processing

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1512
Author(s):  
Helmut Münstedt
Keyword(s):  
Polymer Melts ◽  
Extensional Flow ◽  
Elongational Flow ◽  
Fused Deposition Modelling ◽  
Extrudate Swell ◽  
Fused Deposition ◽  
Rigid Particles ◽  
Experimental Parameters ◽  
Slit Die

While the uniaxial elongational viscosity is widely investigated, and its relevance for processing is described in the literature, much less has been published on the recoverable extensional flow of polymer melts. This paper presents a short overview of the dependencies of the recoverable elongation on the molecular structure of a polymer, and on some experimental parameters. Its main focus lies on the discussion of processing operations and applications that are largely affected by the elastic components of elongational flow. The recoverable portions of stretched films are considered, and the exploitation of the shrinkage of films, due to the recovery of frozen recoverable deformations, and its role for applications are addressed. The analysis of measurements of velocity fields in the entry region of a slit die and results on the determination of the recoverable elongation from uniaxial experiments, according to the literature, lead to the conclusion of dominant elastic extensions. Considering these facts, the assumptions for Cogswell’s widely used method of determining elongational viscosities under processing conditions from entrance flow are not realistic. As examples of a direct application of extrudate swell from short dies for processing, pelletizing and fused deposition modelling within additive manufacturing are addressed. The special features of extrudate swell from short dies, and uniaxial recoverable elongation for a polymer filled with rigid particles in comparison to an immiscible polymer blend, are presented and discussed.

Extensional Flow of Polymer Melts

1977 ◽  
Vol 21 (3) ◽  
pp. 429-446 ◽  
Author(s):  
Ramesh N. Shroff ◽  
L. V. Cancio ◽  
Mitsuzo Shida
Keyword(s):  
Polymer Melts ◽  
Extensional Flow

Processing/Structure/Properties Relationships in Polymer Blends for the Development of Functional Polymer Foams

2015 ◽  
Author(s):  
Ali Rizvi ◽  
Chul B. Park
Keyword(s):  
Strain Hardening ◽  
Elastic Properties ◽  
Crystallization Kinetics ◽  
Extensional Flow ◽  
Relaxation Times ◽  
Rheological Behaviour ◽  
Polymer Processing ◽  
Phase Morphology ◽  
Dispersed Phase ◽  
Carbon Dioxide Co2

In this study we present a comprehensive experimental investigation of the effect of polymer blending on the dispersed phase morphology and how the dispersed phase morphology influences the foaming behavior of the semicrystalline polymer matrix using three different material combinations: polyethylene (PE)/polypropylene (PP), PP/polyethylene terephthalate (PET) and PP/polytetrafluoroethylene (PTFE). Samples are prepared such that the dispersed phase domains exhibit either spherical or fibrillated morphologies. Measurements of the uniaxial extensional viscosity, linear viscoelastic properties and crystallization kinetics under ambient pressures and elevated pressures of carbon dioxide (CO2) are performed and the morphological features are identified with the aid of SEM. Batch foaming and lab-scale extrusion foaming experiments are performed, as a screening model for polymer processing, to show the enhancement of the foaming ability as a result of the blend morphology, taking into account the rheological behaviour and the effects of crystallization kinetics. The formation of high aspect ratio fibrils imparts unique characteristics to the semicrystalline matrix such as strain-hardening in uniaxial extensional flow, prolonged relaxation times, pronounced elastic properties and enhanced kinetics of crystallization. In contrast, the regular blends containing spherical dispersed phase domains do not exhibit such properties. Foam processing of the three blends reveals a marked broadening of the foaming window when the dispersed phase domains are fibrillated due to the concurrent increase in crystallization kinetics, improved elastic properties and strain hardening in extensional flow.

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