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Structure, processing and performance of ultra-high molecular weight polyethylene (IUPAC Technical Report). Part 2: crystallinity and supra molecular structure

Bucknall, Clive; Altstädt, Volker; Auhl, Dietmar; Buckley, Paul; Dijkstra, Dirk; Galeski, Andrzej; Gögelein, Christoph; Handge, Ulrich A.; He, Jiasong; Liu, Chen-Yang; Michler, Goerg; Piorkowska, Ewa; Slouf, Miroslav; Vittorias, Iakovos; Wu, Jun Jie

Structure, processing and performance of ultra-high molecular weight polyethylene (IUPAC Technical Report). Part 2: crystallinity and supra molecular structure Thumbnail


Authors

Clive Bucknall

Volker Altstädt

Dietmar Auhl

Paul Buckley

Dirk Dijkstra

Andrzej Galeski

Christoph Gögelein

Ulrich A. Handge

Jiasong He

Chen-Yang Liu

Goerg Michler

Ewa Piorkowska

Miroslav Slouf

Iakovos Vittorias



Abstract

Test methods including OM, SEM, TEM, DSC, SAXS, WAXS, and IR were used to characterise supra-molecular structure in three batches of polyethylene (PE), which had weight-average relative molar masses ¯¯¯¯ M w of approximately 0.6 × 106, 5 × 106, and 9 × 106. They were applied to compression mouldings made by the polymer manufacturer. Electron microscopy showed that powders formed in the polymerization reactor consisted of irregularly shaped grains between 50 and 250 μm in diameter. Higher magnification revealed that each grain was an aggregate, composed of particles between 0.4 and 0.8 μm in diameter, which were connected by long, thin fibrils. In compression mouldings, lamellar thicknesses ranged from 7 to 23 nm. Crystallinity varied between 70 and 75 % in reactor powder, but was lower in compression mouldings. Melting peak temperatures ranged from 138 to 145 °C, depending on processing history. DMTA showed that the glass transition temperature θg was −120 °C for all three grades of polyethylene. IR spectroscopy found negligibly small levels of oxidation and thermal degradation in mouldings. Optical microscopy revealed the presence of visible fusion defects at grain boundaries. It is concluded that relatively weak defects can be characterized using optical microscopy, but there is a need for improved methods that can detect less obvious fusion defects.

Citation

Bucknall, C., Altstädt, V., Auhl, D., Buckley, P., Dijkstra, D., Galeski, A., …Wu, J. J. (2020). Structure, processing and performance of ultra-high molecular weight polyethylene (IUPAC Technical Report). Part 2: crystallinity and supra molecular structure. Pure and Applied Chemistry, 92(9), 1485-1501. https://doi.org/10.1515/pac-2019-0403

Journal Article Type Article
Acceptance Date Mar 20, 2020
Online Publication Date Aug 25, 2020
Publication Date 2020
Deposit Date Dec 9, 2020
Publicly Available Date Mar 29, 2024
Journal Pure and Applied Chemistry
Print ISSN 0033-4545
Electronic ISSN 0033-4545
Publisher International Union of Pure and Applied Chemistry
Peer Reviewed Peer Reviewed
Volume 92
Issue 9
Pages 1485-1501
DOI https://doi.org/10.1515/pac-2019-0403

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