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The effect of biodegradation on surface and bulk property changes of polypropylene, recycled polypropylene and polylactide biocomposites
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
2009 (English)In: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 63, no 8, 1045-1053 p.Article in journal (Refereed) Published
Abstract [en]

Biocomposites were subject to exposure to a mixture of fungi and algae in a microenvironment chamber. Surface and bulk property changes of polypropylene/wood flour, recycled polypropylene/cellulose and polylactide/wood flour were monitored by tensile testing, Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA) and Field Emission Scanning Electron Microscope (FE-SEM). All the biocomposites showed a substantial decrease in toughness after 28 and 56 days of hydrolysis. The ductility increased after 28 and 56 days, but deteriorated after 84 days of hydrolysis. Biofilm formation occurred on all biocomposites even if the polymer itself was inert to biodegradation. The microbial colonization affected mainly the surface properties of polypropylene biocomposites while changes were monitored also in the bulk properties of polylactide biocomposites. The cellulose fibres in the composites gave a more easily colonized surface mainly attributed to water uptake. In the short term perspective, the water uptake offered better conditions for biofilm adhesion, and in the longer perspective the exposure to microorganisms also resulted in mechanical degradation, followed by biodegradation of cellulose. With time this will leave a porous matrix of polypropylene, while biodegradable polymers such as polylactide will degrade in parallel with the fibre part.

Place, publisher, year, edition, pages
2009. Vol. 63, no 8, 1045-1053 p.
Keyword [en]
Biofilm, Biocomposites, Hydrolysis, Biodegradation, Material properties, mechanical-properties, polymeric materials, composites, fibers, cellulose, wood, degradation, absorption, moisture, biofilms
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-19000DOI: 10.1016/j.ibiod.2009.08.003ISI: 000272218800013Scopus ID: 2-s2.0-71849084138OAI: oai:DiVA.org:kth-19000DiVA: diva2:337047
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically 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.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2009:44
Keyword
Sustainable materials, mechanical recycling, polyolefin, reprocessing, accelerated ageing, chromatography, biofilm, microenvironment chamber, environmental degradation, biocomposite, nanocomposite
National Category
Polymer Chemistry
Identifiers
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)
Opponent
Supervisors
Note
QC 20100811Available from: 2009-09-03 Created: 2009-08-25 Last updated: 2010-08-11Bibliographically approved

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Strömberg, EmmaKarlsson, Sigbritt

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