Litvinov, V, Deblieck, R, Clair, C et al. (6 more authors) (2020) Molecular Structure, Phase Composition, Melting Behavior, and Chain Entanglements in the Amorphous Phase of High-Density Polyethylenes. Macromolecules, 53 (13). pp. 5418-5433. ISSN 0024-9297
Abstract
A methodology for estimating the entanglement density in the amorphous phase of semicrystalline polyolefins was developed. The method is based on the analysis of the density of physical network junctions in the amorphous phase by 1H NMR T2 relaxation experiments. The density of the entanglement network was estimated for melt- and high-pressure-crystallized high-density polyethylenes (HDPEs) at temperatures close to and gradually approaching melting. Its value is lower for high-pressure-crystallized HDPE than for the same melt-crystallized polymer. The network of entanglements is characterized by the fraction of entangled network chains, the weight-average molecular weight of the network chains between apparent chain entanglements, Me, and the volume average density of apparent chain entanglements. The entanglement network was studied in a series of low- and high-molecular-weight HDPEs and bimodal HDPE samples with different molecular weight characteristics and densities controlled by different contents of the 1-butene comonomer. It turns out that the molecular weight characteristics of the HDPEs influence the entanglement network. The fraction of network chains and the average density of apparent chain entanglements decrease with decreasing molecular weight Mn due to the “dilution” effect caused by disentangled chain-end segments increasing the Me. The current methodology is of interest for studying the effect of crystallization conditions, molecular structures, and short-chain branches on phase composition, melting behavior, and chain entanglements in the amorphous phase of polyolefins. The method allows estimation of the fraction of network chains, which potentially can form tie-chain segments during deformation. The effect of short-chain branches and molecular weight characteristics on the creep response of polyolefins is discussed.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2020 American Chemical Society. This is an author produced version of an article published in Macromolecules. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Soft Matter Physics (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 25 Aug 2020 11:12 |
Last Modified: | 19 Jun 2021 00:38 |
Status: | Published |
Publisher: | American Chemical Society (ACS) |
Identification Number: | 10.1021/acs.macromol.0c00956 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:164766 |