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| 3. |
- Albertsson, Ann-Christine, et al.
(författare)
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Molecular weight changes and polymeric matrix changes correlated with the formation of degradation products in biodegraded polyethylene
- 1999
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Ingår i: Journal of environmental polymer degradation. - 1064-7546 .- 1572-8900. ; 64, s. 91-99
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Tidskriftsartikel (refereegranskat)abstract
- The molecular weight changes in abiotically and biotically degraded LDPE and LDPE modified with starch and/or prooxidant were compared with the formation of degradation products, The samples were thermooxidized for 6 days at 100 degrees C to initiate degradation and then either inoculated with Arthobacter paraffineus or kept sterile. After 3.5 years homologous series of mono- and dicarboxylic acids and ketoacids were identified by GC-MS in abiotic samples, while complete disappearance of these acids was observed in biotic environments. The molecular weights of the biotically aged samples were slightly higher than the molecular weights of the corresponding abiotically aged samples, which is exemplified by the increase in (M) over bar(n) from 5200 g/mol for a sterile sample with the highest amount of prooxidant to 6000 g/mol for the corresponding biodegraded sample. The higher molecular weight in the biotic environment is explained by the assimilation of carboxylic acids and low molecular weight polyethylene chains by microorganisms. Assimilation of the low molecular weight products is further confirmed by the absence of carboxylic acids in the biotic samples. Fewer carbonyls and more double bonds were seen by FTIR in the biodegraded samples, which is in agreement with the biodegradation mechanism of polyethylene.
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- Hakkarainen, Minna, et al.
(författare)
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Solid phase microextraction (SPME) as an effective means to isolate degradation products in polymers
- 1997
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Ingår i: Journal of environmental polymer degradation. - 1064-7546 .- 1572-8900. ; 5, s. 67-73
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Tidskriftsartikel (refereegranskat)abstract
- A new sample preparation technique, solid phase microextraction (SPME), was compared with direct headspace-GC-MS with respect to the type and amount of identified compounds. Three types of LDPE films containing photosensitising additives according to the Scott-Gilead patents and pure LDPE were used as model substances. The polyethylene films were thermally aged at 80 degrees C after the induction period was surpassed by subjecting the materials to 100 h of UV radiation. The new SPME method was developed using nonpolar poly(dimethylsiloxane) and polar carbowax fibers to extract the low molecular weight products formed in the polyethylene films during aging. Many more products were identified after SPME followed by CC-MS than after direct headspace-GC-MS of the samples. The SPME method allowed the identification of homologous series of carboxylic acids, ketones, and furanones, while direct headspace-GC-MS identified only a few carboxylic acids (C1-C6) and small amounts of some ketones and furanones. In general, SPME was more effective in extracting less volatile products, and in particular, the polar carbowax fiber identified also C7-C12 carboxylic acids and 4-oxopentanoic acid. By SEC and FTIR we confirmed that the number and amount of former degradation products correlated well with the decrease in molecular weights and the amount of formed carbonyl compounds.
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| 7. |
- Albertsson, Ann-Christine, et al.
(författare)
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Emission of volatiles from polymers - A new approach for understanding polymer degradation
- 2006
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 14:1, s. 8-13
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Tidskriftsartikel (refereegranskat)abstract
- Emission of low molar mass compounds from different polymeric materials was determined and the results from the volatile analysis were applied to predict the degree of degradation and long-term properties, to determine degradation rates and mechanisms, to differentiate between biotic and abiotic degradation and for quality control work. Solid-phase microextraction and solid-phase extraction together with GC-MS were applied to identify and quantify the low molar mass compounds. Volatiles were released and monitored at early stages of degradation before any matrix changes were observed by e.g. SEC, DSC and tensile testing. The analysis of volatiles can thus also be applied to detect small differences between polymeric materials and their susceptibility to degradation. The formation of certain degradation products correlated with the changes taking place in the polymer matrix, these indicator products could, thus, be analysed to rapidly predict the degree of degradation in the polymer matrix and further to predict the long-term properties and remaining lifetime of the product.
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- Andersson, Richard L., et al.
(författare)
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Micromechanical Tensile Testing of Cellulose-Reinforced Electrospun Fibers Using a Template Transfer Method (TTM)
- 2012
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 20:4, s. 967-975
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Tidskriftsartikel (refereegranskat)abstract
- A template transfer method (TTM) and a fiber fixation technique were established for fiber handling and micro tensile stage mounting of aligned and non-aligned electrospun fiber mats. The custom-made template had been precut to be mounted on a variety of collectors, including a rapidly rotating collector used to align the fibers. The method eliminated need for direct physical interaction with the fiber mats before or during the tensile testing since the fiber mats were never directly clamped or removed from the original substrate. By using the TTM it was possible to measure the tensile properties of aligned poly(methyl methacrylate) (PMMA) fiber mats, which showed a 250 % increase in strength and 450 % increase in modulus as compared to a non-aligned system. The method was further evaluated for aligned PMMA fibers reinforced with cellulose (4 wt%) prepared as enzymatically derived nanofibrillated cellulose (NFC). These fibers showed an additional increase of 30 % in both tensile strength and modulus, resulting in a toughness increase of 25 %. The fracture interfaces of the PMMA-NFC fibers showed a low amount of NFC pull-outs, indicating favorable phase compatibility. The presented fiber handling technique is universal and may be applied where conservative estimates of mechanical properties need to be assessed for very thin fibers.
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- Eyholzer, Christian, et al.
(författare)
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Dispersion and reinforcing potential of carboxymethylated nanofibrillated cellulose powders modified with 1-hexanol in extruded poly(lactic acid) (PLA) composites
- 2012
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 29:4, s. 1052-1062
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Tidskriftsartikel (refereegranskat)abstract
- Bionanocomposites of poly(lactic acid) (PLA) and chemically modified, nanofibrillated cellulose (NFC) powders were prepared by extrusion, followed by injection molding. The chemically modified NFC powders were prepared by carboxymethylation and mechanical disintegration of refined, bleached beech pulp (c-NFC), and subsequent esterification with 1-hexanol (c-NFC-hex). A solvent mix was then prepared by precipitating a suspension of c-NFC-hex and acetone-dissolved PLA in ice-cold isopropanol (c-NFC-hex sm), extruded with PLA into pellets at different polymer/fiber ratios, and finally injection molded. Dynamic mechanical analysis and tensile tests were performed to study the reinforcing potential of dried and chemically modified NFC powders for PLA composite applications. The results showed a faint increase in modulus of elasticity of 10 % for composites with a loading of 7.5 % w/w of fibrils, irrespective of the type of chemically modified NFC powder. The increase in stiffness was accompanied by a slight decrease in tensile strength for all samples, as compared with neat PLA. The viscoelastic properties of the composites were essentially identical to neat PLA. The absence of a clear reinforcement of the polymer matrix was attributed to poor interactions with PLA and insufficient dispersion of the chemically modified NFC powders in the composite, as observed from scanning electron microscope images. Further explanation was found in the decrease of the thermal stability and crystallinity of the cellulose upon carboxymethylation
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- Isarankura Na Ayutthaya, Siriorn, et al.
(författare)
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Keratin Extracted from Chicken Feather Waste : Extraction, Preparation, and Structural Characterization of the Keratin and Keratin/Biopolymer Films and Electrospuns
- 2015
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 23:4, s. 506-516
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Tidskriftsartikel (refereegranskat)abstract
- In this work, keratin was extracted from chicken feather waste via an environment-friendly method, sulphitolysis method, by using various sodium metabisulphite contents (0.0–0.5 M). Percentage yield and molecular weight of the extracted keratin were characterized by gravimetry and gel electrophoresis (SDS-PAGE), respectively. It was found that the yield increased, with the increase of sodium meta-bisulphite content, to the maximum value of 87.6 % yield, by using sodium meta-bisulphite content at 0.2 M. Molecular weight range of the product also decreased with the increase of the sodium meta-bisulphite content. The extracted keratin, with highest molecular weight ranged between 12 and 20 kDa, was further used for fabricating into fibers by using the electrospinning process. It was found that pure keratin solution could not be electrospun into fiber. However, by blending keratin with more than 10 wt% PLA, the fibers can be prepared. Results from FTIR and DSC also reveal that the crystal structure of the keratin changed from the β-sheet structure (rigid and small displacement characteristic) to the α-helix structure (elastic and large displacement characteristic) after keratin/PLA blends (10–50 wt% keratin) were prepared by the electrospinning method.
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