Modeling the linear viscoelastic properties of metallocene-catalyzed high density polyethylenes with long-chain branching

2005 ◽  
Vol 49 (2) ◽  
pp. 523-536 ◽  
Author(s):  
Seung Joon Park ◽  
Ronald G. Larson
Keyword(s):  
Viscoelastic Properties ◽  
High Density ◽  
Chain Branching ◽  
Long Chain Branching ◽  
Linear Viscoelastic ◽  
Long Chain

Influence of long-chain branching on linear viscoelastic flow properties and dielectric relaxation of polycarbonates

Polymer ◽  
2004 ◽  
Vol 45 (8) ◽  
pp. 2803-2812 ◽  
Author(s):  
Chenyang Liu ◽  
Chaoxu Li ◽  
Peng Chen ◽  
Jiasong He ◽  
Qingrong Fan
Keyword(s):  
Dielectric Relaxation ◽  
Viscoelastic Flow ◽  
Flow Properties ◽  
Chain Branching ◽  
Long Chain Branching ◽  
Linear Viscoelastic ◽  
Long Chain

scholarly journals Modelling of Elongational Flow of HDPE Melts by Hierarchical Multi-Mode Molecular Stress Function Model

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3217
Author(s):  
Leslie Poh ◽  
Esmaeil Narimissa ◽  
Manfred H. Wagner
Keyword(s):  
Stress Function ◽  
High Density Polyethylene ◽  
High Density ◽  
Molecular Characteristics ◽  
Chain Branching ◽  
Data Set ◽  
Long Chain Branching ◽  
Molecular Stress Function ◽  
Multi Mode ◽  
Long Chain

The transient elongational data set obtained by filament-stretching rheometry of four commercial high-density polyethylene (HDPE) melts with different molecular characteristics was reported by Morelly and Alvarez [Rheologica Acta 59, 797–807 (2020)]. We use the Hierarchical Multi-mode Molecular Stress Function (HMMSF) model of Narimissa and Wagner [Rheol. Acta 54, 779–791 (2015), and J. Rheology 60, 625–636 (2016)] for linear and long-chain branched (LCB) polymer melts to analyze the extensional rheological behavior of the four HDPEs with different polydispersity and long-chain branching content. Model predictions based solely on the linear-viscoelastic spectrum and a single nonlinear parameter, the dilution modulus GD for extensional flows reveals good agreement with elongational stress growth data. The relationship of dilution modulus GD to molecular characteristics (e.g., polydispersity index (PDI), long-chain branching index (LCBI), disengagement time τd) of the high-density polyethylene melts are presented in this paper. A new measure of the maximum strain hardening factor (MSHF) is proposed, which allows separation of the effects of orientation and chain stretching.

Effect of long chain branching on linear-viscoelastic melt properties of polyolefins

e-Polymers ◽  
2002 ◽  
Vol 2 (1) ◽  
Author(s):  
Juanfran Vega ◽  
Marina Aguilar ◽  
Jon Peón ◽  
David Pastor ◽  
Javier Martínez-Salazar
Keyword(s):  
Side Chain ◽  
Relaxation Processes ◽  
Chain Branching ◽  
Long Chain Branching ◽  
Polymer Main Chain ◽  
Additional Branch ◽  
Linear Viscoelastic ◽  
Long Chain ◽  
Made In ◽  
Number Of Branches

AbstractThe aim of this review is to provide evidence that rheological testing is a potent tool for characterising polymers in the melt. An effort has been made in order to gather results in conventional and model polyolefins, and correlating them with phenomena occurring at the molecular level. We have focused our interest on long chain branching (LCB). In the case of materials containing long side-chain branches, strong effects on viscosity, elastic character and activation energy of flow are general features. Literature results mostly indicate that the effect of polydispersity on these parameters could be very similar to that expected due to the presence of LCB - notwithstanding that the effects of LCB seem to be stronger than those due to polydispersity for a given molecular weight. Different relaxation processes appear as a consequence of the presence of LCB: slower terminal relaxation behaviour than of linear counterparts, and faster additional branch relaxation at higher frequencies, clearly distinguishable from polydispersity effects. To measure the amount of LCB from limited viscoelastic data and molecular properties seems to be a suitable instrument to explain the rheological features of the different polymers, but it fails when the results are compared with measured values of LCB density in model polymers. The actual framework leads us to say that the number of branches is less important than the topology itself. Therefore, the position and architecture of the branches along the polymer main chain are the main factors that control the rheology of the material.

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