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Comparison of extraction methods for sampling of low molecular compounds in polymers degraded during recycling
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-2139-7460
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.ORCID iD: 0000-0002-5394-7850
2008 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 44, no 6, 1583-1593 p.Article, review/survey (Refereed) Published
Abstract [en]

The demand for mechanical recycling of plastic waste results in an increasing amount of recycled polymeric materials available for development of new products. In order for recycled materials to find their way into the material market, high quality is demanded. Thereby, a complete and closed loop of polymeric materials can be achieved successfully. The concept of high quality for recycled plastics imply that besides a pure fraction of e.g. polyethylene (PE) or polypropylene (PP), containing only minor trace amount of foreign plastics, knowledge is required about the type and amount of low molecular weight (LMW) compounds. During long-term use (service-life), products made of polymeric materials will undergo an often very slow degradation where a series of degradation products are formed, in parallel, additives incorporated in the matrix may also degrade. These compounds migrate at various rates to the surrounding environment. The release rate of LMW products from plastics depends on the initiation time of degradation and the degradation mechanisms. For polymers the formation of degradation products may be initiated already during processing, and subsequent use will add products coming from the surrounding environment, e.g. fragrance and aroma compounds from packaging. During recycling of plastics, emissions which contain a series of different LMW compounds may reach the environment leading to unwanted exposure to additives and their degradation residues as well as degradation products of polymers. Several extraction techniques are available for sampling of LMW compounds in polymers before chromatographic analysis. This paper reviews and compares polymer dissolution, accelerated solvent extraction (ASE), microwave assisted extraction (MAE), ultrasound assisted extraction (UAE), super critical fluid extraction (SFE), soxhlet extraction, head-space extraction (HS), head-space solid phase micro extraction (HS-SPME), and head-space stir bar sorptive extraction (HSSE) as appropriate sampling methods for LMW compounds in recycled polymers. Appropriate internal standards useful for these kinds of matrices were selected, which improved the possibility for later quantification. Based on the review of extraction methods, the most promising techniques were tested with industrially recycled samples of HDPE and PP and virgin HDPE and PP for method comparison.

Place, publisher, year, edition, pages
2008. Vol. 44, no 6, 1583-1593 p.
Keyword [en]
extraction, recycled polymers, accelerated solvent extraction (ASE), microwave assisted extraction (MAE), head-space solid phase micro, extraction (HS-SPME), head-space stir bar sorptive extraction (HSSE), supercritical-fluid extraction, microwave-assisted extraction, solid-phase microextraction, performance liquid-chromatography, soxhlet, extraction, solvent-extraction, gas-chromatography, additives, polypropylene, polyethylene
National Category
Polymer Chemistry
URN: urn:nbn:se:kth:diva-17686DOI: 10.1016/j.eurpolymj.2008.03.027ISI: 000257619000001ScopusID: 2-s2.0-44649086397OAI: diva2:335731
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-01-13Bibliographically approved
In thesis
1. Long-term Properties of Sustainable Polymeric Materials: Mechanical Recycling and Use of Renewable Resources
Open this publication in new window or tab >>Long-term Properties of Sustainable Polymeric Materials: Mechanical Recycling and Use of Renewable Resources
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

New strategies for management of the accumulating amounts of plastic waste are required, to achieve a sustainable development in terms of material production and use. After service life, the materials should be recovered and recycled efficiently to provide a valuable resource for future applications. Optimised use of amended recycled polymeric materials, e.g. reinforced with natural fibres, and polymers from renewable resources give rise to polymeric materials with lower environmental impact. The recovery of plastic waste by means of mechanical recycling is a favourable route for preservation of raw materials and energy. Deficient knowledge about the overall quality of the recyclates, such as the degree of degradation, mixing and contamination, has resulted in restricted subsequent application of the recycled materials. Therefore, quality assessment of the recycled polymers is required for guaranteed performance in future applications.

Recycling and service life of polyolefins (PP and HDPE) were modelled by multiple reprocessing and thermo-oxidation. The material properties of the polyolefins were affected by both thermo-oxidation and thermo-mechanical degradation. PP showed higher susceptibility to reprocessing and elevated formation of low molecular weight compounds compared to HDPE. Release of the compounds during service life is anticipated on account of the extensive migration of these volatiles during thermal ageing.

Microenvironment chambers simulating outdoor environmental conditions were designed to monitor biofilm formation on silicon rubber composite materials. Furthermore, the microenvironments were successfully used to determine the long-term properties of biocomposites, consisting of conventional or biodegradable polymeric matrices and natural fibres as reinforcement, by subjecting the materials to a hydrolytic environment and microbiological degradation. Facilitated surface colonisation due to the presence of cellulose fibres in the composites was mainly attributed to water uptake. Biodegradation of PP biocomposites influenced mainly the surface properties whereas for PLA the bulk properties were also highly affected.

PP-clay nanocomposites were subjected to simulated environmental degradation by thermo-oxidation, daylight photo-oxidation and exposure to forest soil. Increased crystallinity and surface oxidation were detected after thermo-oxidation of the materials. The presence of clay promoted formation of carbonyl compounds during photo-oxidation and water uptake during exposure to soil.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 62 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2009:44
Sustainable materials, mechanical recycling, polyolefin, reprocessing, accelerated ageing, chromatography, biofilm, microenvironment chamber, environmental degradation, biocomposite, nanocomposite
National Category
Polymer Chemistry
urn:nbn:se:kth:diva-10934 (URN)978-91-7415-402-3 (ISBN)
Public defence
2009-09-17, F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00 (English)
QC 20100811Available from: 2009-09-03 Created: 2009-08-25 Last updated: 2010-08-11Bibliographically approved

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