Aging and Degradation of LDPE by Compact NMR

Teymouri, Yadollah; Kwamen, Rance; Blümich, Bernhard

doi:10.1002/mame.201500156

Cited by 21 publications

(31 citation statements)

References 28 publications

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“…This is accompanied by a reduction in the fraction of the interface domains and an increase in the fraction of the amorphous domains. The latter result agrees well with the variations in the chain mobility of the soft domains (Figure a) and the phase composition determined by compact NMR . Compared to thermal aging, the phase composition of LDPE shows a slighter variation upon swelling in n‐hexane where the rigid fraction determined by compact NMR at room temperature increases by almost one percent by weight .…”

Section: Resultssupporting

confidence: 86%

“…To understand the structural changes induced by thermal aging and observed by NMR, FTIR spectra were measured and the carbonyl index I CO determined for different aging times and temperatures (Figure a). For the LDPE samples aged at 80 and 90° C, a gradual increase in I CO is observed, indicating the occurrence of chain scission even at short exposure times . These results were corroborated by SEC measurements which revealed that the molecular weight decreases in the whole range of exposure times and at all three temperatures.…”

Section: Resultssupporting

confidence: 62%

“…In contrast, chemical degradation, largely through chain scissions in the soft amorphous phase and usually reflected through an increase in the chain mobility of this region, dominates at longer exposure times and/or higher temperatures. The chain scissions lead to: 1) an increase in the amount of the crystalline phase through chemo‐crystallization and 2) a reduction in the molecular weight as suggested by FTIR measurements and confirmed by GPC measurements . After certain exposure times, both the molecular weight and the interlamellar distance reach critical values and the sample undergoes a ductile‐brittle transition .…”

Section: Resultsmentioning

confidence: 85%

“…Hence, for thermo‐oxidative aging, physical crystallization and chemical degradation need to be considered together . The increase in the T 2eff of the soft domains relates to chain scission dominating crystallization . The existence of chemical degradation has been confirmed by observing the carbonyl index with FTIR spectroscopy and the changes in molecular weight with size‐exclusion chromatography …”

Section: Resultsmentioning

confidence: 99%

“…a) Thermal aging in air (adapted from Ref. ) (b) swelling in n ‐hexane. For comparison, the relaxation times are normalized to the relaxation time of the untreated sample.…”

Section: Resultsmentioning

confidence: 99%

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Impact of Exposure Conditions on the Morphology of Polyethylene by Compact NMR

Teymouri

Adams

Blümich

2018

Macromolecular Symposia

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Today many polyethylene (PE) products are employed in long‐term applications that require the use of elevated temperatures and/or contact with different solvents. Both the exposure to heat and solvents can result in morphological changes, compromising the mechanical stability of the material. Disentangling morphological changes induced by either type of exposure and understanding their combined effect is crucial for establishing reliable structure‐property relationships. This, in turn, requires sensitive analytical methods that can probe the complex morphology of PE both in the laboratory and on site. Among existing analytical methods, NMR with compact devices have recently become a key analytical tool for the detailed morphological characterization of a variety of solid polymers including PE. This current work reviews the potential of compact NMR for monitoring and quantifying morphological changes in PE exposed to the aforementioned external conditions. To prove the reliability of compact proton NMR relaxation measurements, the results are compared with data from conventional high‐field proton wide‐line NMR spectroscopy, DSC, and FTIR spectroscopy. It could be shown that simple, static proton relaxation measurements garner detailed information about the exposure‐induced morphological changes through the quantification of phase composition and chain dynamics. Moreover, the NMR method has a key advantage over other methods, because the chain mobility of the soft amorphous phase is a very sensitive microscopic parameter under exposure conditions. The various presented examples and the good agreement of the NMR results with those of other analytical methods show that low‐field NMR is a promising option for in‐situ aging studies.

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Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 62%

Section: Resultsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

“…a) Thermal aging in air (adapted from Ref. ) (b) swelling in n ‐hexane. For comparison, the relaxation times are normalized to the relaxation time of the untreated sample.…”

Section: Resultsmentioning

confidence: 99%

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Impact of Exposure Conditions on the Morphology of Polyethylene by Compact NMR

Teymouri

Adams

Blümich

2018

Macromolecular Symposia

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NMR mit Tischgeräten und deren Anwendungen von der Materialwissenschaft bis zur organischen Chemie

Blümich

Singh

2017

Angewandte Chemie

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Die NMR‐Spektroskopie ist eine unverzichtbare Analysemethode. Bis vor kurzem erforderten die Geräte viel Platz, waren teuer und schwer zu bedienen. Dies hat sich mit der Einführung kompakter NMR‐Spektrometer geändert, die sich für die Analyse kleiner Moleküle auf der Laborbank eignen. Solche Spektrometer sind mit Permanentmagneten für 1H‐NMR‐Frequenzen zwischen 40 und 80 MHz ausgestattet. Erst seit wenigen Jahren gibt es kleine Permanentmagnete mit homogenen Magnetfeldern für hochaufgelöste Spektroskopie. Tischgeräte mit inhomogenen Feldern werden schon seit 40 Jahren zur Charakterisierung von Lebensmitteln und Materialien über Relaxations‐ und Diffusionsmessungen genutzt. Ähnliche NMR‐Geräte messen diese Parameter im Streufeld außerhalb des Magneten. Sie werden zur Untersuchung von Bohrlochwänden in Ölquellen sowie für zerstörungsfreie Analysenverwendet. Der gegenwärtige Stand von NMR‐Spektroskopie, ‐Bildgebung und ‐Relaxometrie wird hier anhand repräsentativer Beispiele beschrieben.

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Desktop NMR and Its Applications From Materials Science To Organic Chemistry

2017

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NMR spectroscopy is an indispensable method of analysis in chemistry, which until recently suffered from high demands for space, high costs for acquisition and maintenance, and operational complexity. This has changed with the introduction of compact NMR spectrometers suitable for small-molecule analysis on the chemical workbench. These spectrometers contain permanent magnets giving rise to proton NMR frequencies between 40 and 80 MHz. The enabling technology is to make small permanent magnets with homogeneous fields. Tabletop instruments with inhomogeneous fields have been in use for over 40 years for characterizing food and hydrogen-containing materials by relaxation and diffusion measurements. Related NMR instruments measure these parameters in the stray field outside the magnet. They are used to inspect the borehole walls of oil wells and to test objects nondestructively. The state-of-the-art of NMR spectroscopy, imaging and relaxometry with compact instruments is reviewed.

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Aging and Degradation of LDPE by Compact NMR

Cited by 21 publications

References 28 publications

Impact of Exposure Conditions on the Morphology of Polyethylene by Compact NMR

Impact of Exposure Conditions on the Morphology of Polyethylene by Compact NMR

NMR mit Tischgeräten und deren Anwendungen von der Materialwissenschaft bis zur organischen Chemie

Desktop NMR and Its Applications From Materials Science To Organic Chemistry

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