Characterizing long-chain branching in commercial HDPE samples via linear viscoelasticity and extensional rheology

It is well established that polymer chain architecture and the distribution of molecular weight play a key role in the flow behavior (processing) and performance of a given polymer material. Long-chain branching (LCB) in particular is known to strongly affect the processability and the material perf...

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Bibliographic Details
Published in:Rheologica acta 2020-11, Vol.59 (11), p.797-807
Main Authors: Morelly, Samantha L., Alvarez, Nicolas J.
Format: Article
Language:English
Subjects:
Chain branching
Chains (polymeric)
Characterization and Evaluation of Materials
Chemistry and Materials Science
Complex Fluids and Microfluidics
Food Science
High density polyethylenes
Materials Science
Mechanical Engineering
Molecular chains
Molecular weight
Molecular weight distribution
Original Contribution
Polydispersity
Polymer Sciences
Polymers
Rheological properties
Rheology
Size exclusion chromatography
Soft and Granular Matter
Strain hardening
Viscoelasticity
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Summary:It is well established that polymer chain architecture and the distribution of molecular weight play a key role in the flow behavior (processing) and performance of a given polymer material. Long-chain branching (LCB) in particular is known to strongly affect the processability and the material performance of polymers. Often branching is a result of the polymerization process and therefore must be quantified in every sample. We study four commercial high-density polyethylene (HDPE) samples with unknown degrees of polydispersity and LCB. We first use size-exclusion chromatography and linear shear rheology to identify differences in molecular weight, polydispersity, and LCB. Each material is then tested in constant rate and constant stress uniaxial extension using a filament stretching rheometer to quantify extensional viscosity and strain hardening. Correlations between nonlinear extensional rheology, LCB and polydispersity are discussed. We show that the combination of the van Gurp-Palmen plot and extensional rheology allows for a full characterization of the LCB fraction and their effect on extensional rheology.
ISSN:0035-4511
1435-1528
DOI:10.1007/s00397-020-01233-5