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Updated: Nov 2, 2025
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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
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Rheology of Crystallizing LLDPE
Marat Andreev1, David Nicholson1, Anthony Kotula2
1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA.
Journal of Rheology
|June 16, 2021
Summary
This study models polymer crystallization in linear low-density polyethylene (LLDPE) using rheology and Raman spectroscopy. A slip-link model, incorporating dangling segments, accurately captures viscosity and elasticity changes during LLDPE crystallization.
Area of Science:
- Polymer Science
- Materials Science
- Rheology
Background:
- Polymer crystallization is crucial in plastic manufacturing.
- Linear low-density polyethylene (LLDPE) properties are tunable via short-chain branching (SCB).
- Understanding LLDPE crystallization dynamics is key for process optimization.
Purpose of the Study:
- To simultaneously measure rheology and Raman spectra during LLDPE crystallization.
- To model the rheological behavior of entangled LLDPE melts as a function of crystallinity.
- To refine the slip-link model for entangled polymers with SCB.
Main Methods:
- Utilized a Rheo-Raman microscope for simultaneous measurements.
- Employed a slip-link model to describe rheological behavior.
- Characterized industrial-grade LLDPEs with broad polydispersity and SCB.
Main Results:
- The slip-link model was adapted to include dangling segments for LLDPE.
- The modified model quantitatively captured viscosity and elasticity evolution with crystallization.
- Model successfully described rheological data across the linear regime for two LLDPE grades.
Conclusions:
- The slip-link model, with modifications, effectively describes LLDPE crystallization.
- Dangling segments are necessary to accurately model rheology in branched polymers like LLDPE.
- This approach provides quantitative insights into polymer melt behavior during processing.
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