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| 3. |
- Badía, José David, et al.
(författare)
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Thermal analysis applied to the characterization of degradation in soil of polylactide : II. on the thermal stability and thermal decomposition kinetics
- 2010
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Ingår i: Polymer degradation and stability. - : Elsevier. - 0141-3910 .- 1873-2321. ; 95:11, s. 2192-2199
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Tidskriftsartikel (refereegranskat)abstract
- The disposal stage of polylactide (PLA) was assessed by burying it in active soil following an international standard. Degradation in soil promotes physical and chemical changes in the polylactide properties. The characterization of the extent of degradation underwent by PLA was carried out by using Thermal Analysis techniques. In this paper, studies on the thermal stability and the thermal decomposition kinetics were performed in order to assess the degradation process of a commercial PLA submitted to an accelerated soil burial test by means of multi-linear-non-isothermal thermogravimetric analyses. Results have been correlated to changes in molecular weight, showing the same evolution as that described by the parameters of thermal stability temperatures and apparent activation energies. The decomposition reactions can be described by two competitive different mechanisms: Nucleation model (A2) and Reaction Contracting Volume model (R3). The changes in the kinetic parameters and kinetic models are in agreement with the calorimetric and dynamic-mechanical-thermal results, presented in the Part I of the study [1]. © 2010 Elsevier Ltd. All rights reserved.
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| 4. |
- Moriana, Rosana, et al.
(författare)
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Assessing the influence of cotton fibers on the degradation in soil of a thermoplastic starch-based biopolymer
- 2010
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Ingår i: Polymer Composites. - : Wiley. - 0272-8397 .- 1548-0569. ; 31:12, s. 2102-2111
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Tidskriftsartikel (refereegranskat)abstract
- Biocomposites consisting of cotton fibers and a commercial starch-based thermoplastic were subjected to accelerated soil burial test. Fourier transform infrared (FTIR) spectrometry analysis was carried out to provide chemical-structural information of the polymeric matrix and its reinforced biocomposites. The effects that take place as a consequence of the degradation in soil of both materials were studied by FTIR-ATR, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). When the polymeric matrix and the reinforced biocomposite are submitted to soil burial test, the infrared studies display a decrease in the C=O band associated to the ester group of the synthetic component as a consequence of its degradation. The crystalline index of both materials decreased as a function of the degradation process, where the crystalline structure of the reinforced biocomposite was the most affected. In accordance, the degraded reinforced biocomposite micrographs displayed a more damaged morphology and fracture surface than the degraded polymeric matrix micrographs. On the other hand, the same thermal decomposition regions were assessed for both materials, regardless of the degradation time. Kissinger, Criado, and Coats-Redfern methods were applied to analyze the thermogravimetric results. The kinetic triplet of each thermal decomposition process was determined for monitoring the degradation test. The thermal study confirms that starch was the most biodegradable polymeric matrix component in soil. However, the presence of cotton fiber modified the degradation rate of both matrix components; the degradability in soil of the synthetic component was slightly enhanced, whereas the biodegradation rate of the starch slowed down as a function of the soil exposure time. © 2010 Society of Plastics Engineers.
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| 5. |
- Moriana, Rosana, et al.
(författare)
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Improved thermo-mechanical properties by the addition of natural fibres in starch-based sustainable biocomposites
- 2011
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 42:1, s. 30-40
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Tidskriftsartikel (refereegranskat)abstract
- Sustainable biocomposites based on thermoplastic starch copolymers (Mater-Bi KE03B1) and biofibres (cotton, hemp and kenaf) were prepared and characterised in terms of their thermo-mechanical and morphological properties. Biocomposites exhibit improved thermal stability and mechanical properties in comparison with the Mater-Bi KE. Biofibres act as suitable thermal stabilizers for the Mater-Bi KE, by increasing the maximum decomposition temperature and the Ea associated to the thermal decomposition process. Biofibre addition into the Mater-Bi KE results in higher storage modulus and in a reduction of the free-volume-parameter associated to the Mater-Bi KE glass transition. The influence of different biofibres on the thermo-mechanical properties of the biocomposites has been discussed. Hemp and kenaf enhance the thermal stability and reduce the free volume-parameter of Mater-Bi KE more significantly than cotton fibres, although the latter exhibits the highest mechanical performance. These differences may be explained by the improved interaction of lignocellulosic fibres with the Mater-Bi KE, due to the presence of hemicellulose and lignin in their formulation. © 2010 Elsevier Ltd. All rights reserved.
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| 6. |
- Moriana, Rosana, et al.
(författare)
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Reinforced biocomposites with guaranteed degradability in soil
- 2010
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Ingår i: Plastics Research Online. - : Society of Plastics Engineers.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The addition of cotton fibers to a starch-based commercial material maintains its thermal stability and assures its biodegradation.
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| 7. |
- Strömberg, Emma, et al.
(författare)
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Characterisation techniques for quality assessment of recycled plastics
- 2005
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Polymers suffer physical and chemical changes and they interact with impurities during their processing and service life. Quality assessment is very important to guarantee a suitable use of recycled plastics in further applications. Reprocessing and accelerated ageing of PP, HDPE and HIPS were performed and the materials were analysed by spectroscopic techniques, thermal analysis and tensile tests to study the effects of the recycling processes and to assess the quality properties of recyclates.
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| 8. |
- Strömberg, Emma
(författare)
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Long-term Properties of Sustainable Polymeric Materials : Mechanical Recycling and Use of Renewable Resources
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 9. |
- Strömberg, Emma, et al.
(författare)
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Quality assessment of recycled plastics
- 2005
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Konferensbidrag (refereegranskat)abstract
- Polymers are subjected to physical and chemical changes during their processing and service life, and they may also interact with impurities that can alter their composition. These changes substantially modify the stabilization mechanisms and the mechanical properties of recycled polymers. Consequently, quality assessment is a matter of significant importance in order to guarantee a suitable employment of recycled plastic materials in further applications. Latest research has focused on the employment of new and reliable techniques for the characterization of recycled polyolefins and the determination of low molecular weight compounds contained in recycled materials. Simulated recycling of polypropylene (PP), high density polyethylene (HDPE) and high-impact polystyrene (HIPS) was carried out in order to assess the changes occurring in the materials during repeated processing. The materials were also subjected to accelerated ageing so as to simulate their performance during service life. The samples were analysed with spectroscopic techniques, DSC (Differential Scanning Calorimetry) and tensile testing. Alterations in melt index were also investigated. Low-molecular weight compounds were extracted from the recycled plastics and analyzed by chromatographic techniques coupled with mass spectrometry. The results of the analyses were compared with corresponding data from recycled materials collected at industrial recycling centres so as to reach a deeper knowledge about the complex chemical composition and to assess the quality properties of recyclates.
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| 10. |
- Vilaplana, Francisco, et al.
(författare)
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Analysis of brominated flame retardants in styrenic polymers : Comparison of the extraction efficiency of ultrasonication, microwave-assisted extraction and pressurised liquid extraction
- 2008
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1196:1-2, s. 139-146
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Tidskriftsartikel (refereegranskat)abstract
- The extraction efficiency of pressurised liquid extraction (PLE), microwave-assisted extraction (MAE), and ultrasonic-assisted extraction (UAE) under different conditions has been compared for the recovery of the most commonly employed brominated flame retardants (BFRs) from styrenic polymeric Matrixes. A HPLC-MS/MS method has been proposed for the simultaneous separation and quantification of tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD) diastereomers, and decabromodiphenyl ether (deca-BDE) in the polymeric extracts. PLE results in complete extraction of TBBPA and HBCD (95-100% recovery), and intermediate recovery Fates for deca-BDE (50%). MAE, on the other hand, gives comparable performance to PLE for HBCD, but lower extraction yields for TBBPA and mainly deca-BDE. Ultrasonication, finally, offers relatively low extraction recoveries (10-50%). The proposed analytical procedures could be used for the effective identification and quantification of BFRs in styrenic plastics and for quality purposes in recycling facilities that deal with styrenic fractions from waste electrical and electronic equipment (WEEE).
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