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Chromatography and extraction techniques for new evaluation methods of polyolefins long-term performance
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Chromatography and extraction techniques, and also chemiluminescence have been utilized to develop new rapid and informative tools in the evaluation of long-term properties and environmental effects of polymeric materials.

Methods were developed for classification of materials and for early and rapid degradation detection. Degradable polyethylene films were classified on the basis of their incorporated prooxidant systems using chromatographic fingerprinting of carboxylic acids, the dominating type of degradation product. The fingerprints were also shown to be useful for prediction of the degradation states and evaluation of the degradation mechanisms. Classification and prediction models were obtained by Multivariate Data Analysis, where the diacids were grouped according to both their type of prooxidant system and their state of degradation. The use of total luminescence intensity (TLI) measurements was also investigated as a means of classifying films and for the early detection of degradation. Comparisons were carried out with common techniques, e.g. FTIR and DSC, after both thermal and UV oxidation. TLI gave an earlier detection of degradation and was more sensitive than carbonyl index and crystallinity measurements to relative differences in degradation between the materials. It furthermore offered complementary information regarding changes in activation energies during the course of the degradation. The results were compared with the chromatographic fingerprints.

A new way to evaluate the low temperature long-term stabilisation efficiency of antioxidants was investigated. A prooxidant was used to obtain catalytic oxidation, instead of using thermal acceleration, to evaluate the stabilisation efficiency of antioxidants at low temperatures but still during reasonably short aging times. Comparisons were made between polypropylene films stabilised with primary antioxidants (Irganox 1076, Irganox 1010 and α-tocopherol) with and without the prooxidant manganese stearate at different temperatures. The relative efficiencies of the antioxidants obtained under prooxidant acceleration test correlated better than thermal acceleration test with the results of a long-term low temperature test.

Additives in plastic packaging materials may affect the environment after migration from the packaging to e.g. their contents, especially if they consist of organic aqueous solutions or oils. The use of Solid-Phase Microextraction (SPME) for the specific task of extraction from an organic aqueous solution such as a simulated food or pharmaceutical solution consisting of 10 vol-% ethanol in water was investigated. Methods were developed and evaluated for extraction both with direct sampling and with headspace sampling. If the extraction method and temperature were selected to suit the concentration levels of the analytes, it was possible to quantify several degradation products simultaneously. Comparisons made with Solid Phase Extraction showed the advantage of SPME for this purpose.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , p. 86
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2005:20
Keywords [en]
Chemical engineering, polymer, chromatographic fingerprinting, gas-chromatography – mass spectrometry, GC-MS, degradable polyethylene, prooxidant systems, chemiluminescence, oxidation, degradation mechanisms, accelerated ageing, antioxidants, transformation products, microwave assisted extraction, MAE, solid-phase microextraction, SPME, volatiles, solid phase extraction, SPE
Keywords [sv]
Kemiteknik
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-219ISBN: 91-7178-097-1 (print)OAI: oai:DiVA.org:kth-219DiVA, id: diva2:7935
Public defence
2005-06-16, K2, Teknikringen 28, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20100929Available from: 2005-05-25 Created: 2005-05-25 Last updated: 2010-09-29Bibliographically approved
List of papers
1. Total Luminescence Intensity as a Tool to Classify Degradable Polyethylene Films by Early Degradation Detection and Changes in Activation Energy
Open this publication in new window or tab >>Total Luminescence Intensity as a Tool to Classify Degradable Polyethylene Films by Early Degradation Detection and Changes in Activation Energy
2003 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 4, no 4, p. 900-907Article in journal (Refereed) Published
Abstract [en]

Total luminescence intensity (TLI) was shown to be a valuable tool to monitor early degradation and thereby classify degradable polyethylene. The photo oxidation and thermal oxidation of polyethylene films containing different prooxidant systems were monitored. The chemiluminescence results were compared with results from FTIR, DSC, and SEC measurements. TLI gave an earlier detection of degradation and offered complementary information regarding changes in activation energies during the course of the degradation. TLI measurements were more sensitive to relative differences in degradation between the materials than the carbonyl index and crystallinity measurements, especially in the case of the UV-aged samples.

Keywords
Chemiluminescence, Degradation, Differential scanning calorimetry, Fourier transform infrared spectroscopy, Photooxidation, Polyethylenes, Thermooxidation, Crystallinity
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5136 (URN)10.1021/bm025752v (DOI)000184360400007 ()
Note
QC 20100929Available from: 2005-05-25 Created: 2005-05-25 Last updated: 2017-12-04Bibliographically approved
2. Chromatographic Fingerprinting - a Tool for Classification and for Predicting the Degradation State of Degradable Polyethylene
Open this publication in new window or tab >>Chromatographic Fingerprinting - a Tool for Classification and for Predicting the Degradation State of Degradable Polyethylene
2005 (English)In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 89, no 1, p. 50-63Article in journal (Refereed) Published
Abstract [en]

The number of degradable polyethylene films on the market is increasing. These degradable films show different degradation behaviour depending on the pro-oxidant system incorporated in them. The degradation of the films gives rise to complex collections of degradation products. The key question in this work was to classify the types of pro-oxidant systems in degradable polyethylene films and the state of degradation of the films. The classification was performed with chromatographic fingerprints of carboxylic acids, the most abundant type of degradation product. The acids were extracted from films oxidised at 80 ° C and were thereafter methylated and analysed by GC-MS. Classification and prediction models were obtained by Multivariate Data Analysis. The diacids were grouped according to both the type of pro-oxidant system and the state of degradation. This showed that both the type of pro-oxidant system and the state of degradation are predictable from the diacid fingerprints. The monoacids were shown to be useful for classifying materials from their initial compositions of stearates but not for predicting the degradation state. The goal was also to see how changes in activation energies for hydroperoxides, noticed earlier with chemiluminescence, were reflected in the degradation mechanisms. The observed increase in chemiluminescence peak temperature of the polyoctylene-containing film was related to the initial degradation of the polyoctylene.

Keywords
classification, prediction, chromatographic fingerprinting, degradation mechanisms, pro-oxidant systems, chemiluminescence
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-5137 (URN)10.1016/j.polymdegradstab.2005.01.002 (DOI)000229569500008 ()2-s2.0-17044390382 (Scopus ID)
Note
QC 20100903Available from: 2005-05-25 Created: 2005-05-25 Last updated: 2017-12-04Bibliographically approved
3. Solid-Phase Microextraction for Qualitative and Quantitative Determination of Migrated Degradation Products of Antioxidants in an Organic Aqueous Solution
Open this publication in new window or tab >>Solid-Phase Microextraction for Qualitative and Quantitative Determination of Migrated Degradation Products of Antioxidants in an Organic Aqueous Solution
2005 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1080, no 2, p. 107-116Article in journal (Refereed) Published
Abstract [en]

 Low molecular weight aromatic substances may migrate out from plastic packaging to their contents, especially if they consist of organic aqueous solutions or oils. It is, therefore, extremely important to be able to identify and quantify any migrated substances in such solutions, even at very low concentrations. We have in this work investigated and evaluated the use of solid-phase microextraction for the specific task of extraction from an organic aqueous solution such as a simulated pharmaceutical solution consisting of 10 vol.% ethanol in water. The goal was furthermore to investigate the possibility of simultaneously identifying and quantifying the substances in spite of differences in their chemical structures. Methods were developed and evaluated for extraction both with direct sampling and with headspace sampling. Difficulties appeared due to the ethanol in the solution and the minute amounts of substances present. We have shown that a simultaneous quantification of migrated low molecular weight degradation products of antioxidants using only one fibre is possible if the extraction method and temperature are adjusted in relation to the concentration levels of the analytes. Comparions were made with solid-phase extraction.

Keywords
solid-phase microextraction, SPME, antioxidants, transformation products, migration
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5138 (URN)10.1016/j.chroma.2005.05.028 (DOI)000230238600002 ()2-s2.0-20444436365 (Scopus ID)
Note
QC 20100929. Uppdaterad från Accepted till Published (20100929).Available from: 2005-05-25 Created: 2005-05-25 Last updated: 2017-12-04Bibliographically approved
4. Evaluation of Long-Term Performance of Antioxidants Using Prooxidants instead of Thermal Acceleration
Open this publication in new window or tab >>Evaluation of Long-Term Performance of Antioxidants Using Prooxidants instead of Thermal Acceleration
2005 (English)In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 43, no 19, p. 4537-4546Article in journal (Refereed) Published
Abstract [en]

Evaluation of stabilization efficiencies of different antioxidants in polymers at low temperature and relatively short time was performed using incorporation of a prooxidant for catalytic oxidation. Comparisons were made between polypropylene films stabilized with primary antioxidants (Irganox 1076, Irganox 1010, and α-tocopherol), with or without the prooxidant manganese stearate at different temperatures. A faster degradation was obtained in the presence of a prooxidant than without it. The relative efficiency of the antioxidants at prooxidant acceleration correlated better to low temperature long-term test than at the thermal acceleration. The results were affected by initial differences in the amounts of the antioxidants present after the processing of the films. These differences were corrected for by a recalculation using microwave-assisted extraction (MAE) and high performance liquid chromatography analysis from the exponential decrease in the amount of antioxidant in the films. The fastest comparison of the antioxidants efficiency was obtained from oxidation induction times, using total luminescence intensity measurements, but reliable results could also be obtained from the time to apparent failure.

Keywords
Accelerated aging, Antioxidants, Microwave-assisted extraction, Polyolefins, Stabilization
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-5139 (URN)10.1002/pola.20936 (DOI)000231989400022 ()2-s2.0-27744540061 (Scopus ID)
Note
QC 20100914. Uppdaterad från Accepted till Published (20100914)Available from: 2005-05-25 Created: 2005-05-25 Last updated: 2017-12-04Bibliographically approved

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