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| 2. |
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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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| 4. |
- 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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| 5. |
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| 6. |
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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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| 8. |
- 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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| 9. |
- 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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| 10. |
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| 11. |
- Jonoobi, Mehdi, et al.
(författare)
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A comparison of modified and unmodified cellulose nanofiber reinforced polylactic acid (PLA) prepared by twin screw extrusion
- 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. 991-997
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Tidskriftsartikel (refereegranskat)abstract
- The goal of this work was to evaluate the effect of chemical modification of cellulose nanofibers (CNF) on the properties of polylactic acid (PLA) nanocomposites. Acetylated nanofibers (ACNF), with degree of substitution 1.07, were isolated from acetylated kenaf fibers by mechanical treatments. Acetylated nanofibers showed more hydrophobic properties compared to non-acetylated ones. The results showed that both crystallinity and thermal stability of acetylated nanofibers were lower than non-acetylated ones. The nanocomposites were prepared by premixing two PLA master batches, one with a high concentration of ACNF and the second with CNF. These were diluted to final concentrations (5 wt%) during the extrusion. The morphology studies of PLA and its nanocomposites showed nanofiber aggregates in both materials. The results showed that the tensile and dynamic mechanical properties were enhanced for both acetylated and non-acetylated nanocomposites compared to the neat PLA matrix while no significant improvement was observed for the acetylated nanocomposites compared to non-acetylated ones. However, the storage modulus increased slightly for acetylated nanocomposites compared to non-acetylated ones.
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| 12. |
- Krishnaprasad, R, et al.
(författare)
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Mechanical and thermal properties of bamboo microfibril reinforced polyhydroxybutyrate biocomposites
- 2009
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Ingår i: Journal of Polymers and the Environment. - : Springer New York LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 17:2, s. 109-114
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Tidskriftsartikel (refereegranskat)abstract
- In the present investigation, microfibrils were extracted from raw bamboo and characterized using scanning electron microscope. Composites based on polyhydroxybutyrate (PHB) and bamboo microfibril were prepared with various microfibril loading. The mechanical and thermal properties of the resulting composites were measured. Tensile strength and impact strength of the composites were found to be increasing with increase in the loading of bamboo microfibrils, reached an optimum and thereafter decreased with further increase in microfibril loading. Percentage crystallinity was found to be increasing with increase in fibril loading. Thermal stability of the composite was higher than that of pure PHB. The composite could be developed further for various structural applications.
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| 13. |
- Kumar Ramamoorthy, Sunil, 1987-, et al.
(författare)
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End of life textiles as reinforcements in biocomposites
- 2017
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Ingår i: Journal of Polymers and the Environment. - : Springer. - 1566-2543 .- 1572-8919 .- 1572-8900. ; , s. -12
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Tidskriftsartikel (refereegranskat)abstract
- A number of attempts have been made to recycle cotton/polyester blend woven fabrics after use; however, most of these fabrics are disposed of in landfills. Major part of these blend fabrics are not recycled due to complexity of the fibre arrangement and cannot be separated economically. This study shows that these discarded woven fabrics could be directly used as reinforcements in composites without fibre separation. Uniform alignment in the woven fabric provided consistent properties to the composites. The fabrics were reinforced by soybean-based-bioresins to produce biocomposites. The composites were analysed for mechanical, thermal, viscoelastic and morphological properties. Porosity and wettability of the composites were also evaluated. Results demonstrate that the tensile strength and modulus of over 100 and 10 MPa, respectively, can be obtained without any fibre treatment. Furthermore, impact strength over 70 kJ/m2 was obtained without any chemical treatment on fibres. The porosity of the composites produced was less than 9 vol%. Additionally, the fabrics were treated with alkali in order to improve the fibre–matrix interface and the composite properties were studied. From the economical perspective, these composites can be produced at a low cost as the major component is available for free or low cost.
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| 14. |
- Rodionova, Galina, et al.
(författare)
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TEMPO-mediated oxidation of Norway Spruce and Eucalyptus Pulps : Preparation and Characterization of Nanofibres and Nanofiber Dispersions
- 2013
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 21:1, s. 207-214
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Tidskriftsartikel (refereegranskat)abstract
- This study deals with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of cellulose. Softwood and hardwood pulp fibers were suspended in water and oxidized to various extents at pH 10 and 22 °C using sodium hypochlorite in the presence of TEMPO radical and sodium bromide. This reaction system is known to be the most efficient one for the introduction of both surface carboxyl and aldehyde groups. Important relationships between formation of these functional groups and the fibrillation yield, light transmittance of the water dispersions and degree of polymerization of the oxidized softwood and hardwood pulps were established in the present study. A birefringence test confirmed the presence of nanofibers which according to atomic force microscopy analyses had diameters in the 1. 6-3. 8 nm range.
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| 15. |
- Roy, P. K., et al.
(författare)
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Exploring the Biodegradation Potential of Polyethylene Through a Simple Chemical Test Method
- 2014
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Ingår i: Journal of Polymers and the Environment. - : Springer Nature. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 22:1, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- Oxidatively degradable polyethylene is finding widespread use, particularly in applications such as single use packaging and agriculture. However, the key question which still remains unanswered is the ultimate fate and biodegradability of these polymers. During a short-time frame only the oxidized low molecular weight fraction will be amenable to significant biodegradation. The short-time frame biodegradation potential of different LDPE-transition metal formulations was, thus, explored through a simple chemical extraction of oxidized fraction. In addition the effectiveness of different transitions metals was evaluated by comparing the extractable fractions. Blown LDPE films modified with different transition metal based pro-oxidants were thermo-oxidized at 60 °C over extended periods. The structural changes occurring in the polymer were monitored and the oxidized degradation products formed as a result of the aging process were estimated by extractions with water and acetone. The extractable fraction first increased to approximately 22 % as a result of thermo-oxidative aging and then leveled off. The extractable fraction was approximately two times higher after acetone extraction compared to extraction with water and as expected, it was higher for the samples containing pro-oxidants. Based on our results in combination with existing literature we propose that acetone extractable fraction gives an estimation of the maximum short-term biodegradation potential of the material, while water extractable fraction indicates the part that is easily accessible to microorganisms and rapidly assimilated. The final level of biodegradation under real environmental conditions will of course be highly dependent on the specific environment, material history and degradation time.
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| 16. |
- Sjöqvist, Mia, 1974, et al.
(författare)
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Effect of water content in potato amylopectin starch on microwave foaming process
- 2007
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1572-8919 .- 1566-2543 .- 1572-8900. ; 15:1, s. 43-50
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Tidskriftsartikel (refereegranskat)abstract
- In this study we investigated the role of the water content of extrudates had in foaming capacity and searched for the water content giving the greatest expansion of starch extrudates. Porous structures based on potato amylopectin starch were prepared by extrusion followed by a microwave foaming process. Starch was first extruded with water, in order to incorporate water in the granular structure and achieve gelatinization. Extrudates were conditioned at humidities ranging from 11% to 97%. The water content in the starch extrudates was studied by a water vapor sorption isotherm study. Extrudates were analyzed with light microscopy and wide angle X-ray scattering studies to determine degree of crystallinity. In the second step, extrudates were foamed in a microwave oven. As the water started to boil, it acted as a blowing agent, leaving a porous closed-cell starch structure. The densities and the expansion ratios of the foamed samples are determined. Porosity was studied with environmental scanning electron microscopy. Mechanical properties as a function of the surrounding humidity were analyzed with dynamic mechanical analysis. We found that the maximal degree of expansion was in extrudates conditioned at 33% and 54% RH and having water content of 11.2% and 13.4%, respectively. This level of water is sufficient to expand the extrudate to a maximum level but not high enough to plasticize the starch and cause cell collapse after treatment.
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| 17. |
- Türe, Hasan, et al.
(författare)
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Properties of Wheat-Gluten/Montmorillonite Nanocomposite Films Obtained by a Solvent-Free Extrusion Process
- 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. ; :4, s. 1038-1045
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Tidskriftsartikel (refereegranskat)abstract
- This is, to our knowledge, the first study of wheat-gluten-based nanocomposite films prepared by a solvent-free extrusion process. Wheat gluten/montmorillonite nanocomposite films were obtained in a single screw-extruder using urea as a combined denaturant and plasticizer. The oxygen permeability and water vapor transmission rate of the films decreased by respectively factors of 1. 9 and 1. 3 when 5 wt.% clay was added. At the same time, the stiffness increased by a factor of 1. 5, without any critical loss of extensibility. Field emission scanning electron microscopy (FE-SEM) and Energy-dispersive X-ray analysis indicated that the clay particles were layered mainly in the plane of the extruded film. It was possible to identify individual platelets/tactoids with FE-SEM and, together with findings from transmission electron microscopy, atomic force microscopy and X-ray diffraction, it was concluded that the clay existed as individual clay platelets, intercalated tactoids and agglomerates. Thermogravimetric analysis showed that the thermal stability of the extrudates was improved by the addition of clay.
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| 18. |
- Wretfors, Christer, et al.
(författare)
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Use of Industrial Hemp Fibers to Reinforce Wheat Gluten Plastics
- 2009
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 17:4, s. 259-266
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Tidskriftsartikel (refereegranskat)abstract
- The next generation of manufactured products must be sustainable and industrially eco-efficient, making materials derived from plants an alternative of particular interest. Wheat gluten (WG) is an interesting plant material to be used for production of plastic similar materials due to its film-forming properties. For usage of plastics in a wider range of applications, composite materials with improved mechanical properties are demanded. The present study investigates the possibilities of reinforcing WG plastics with hemp fibers. Samples were manufactured using compression molding (130 A degrees C, 1600 bar, 5 min). Variation in fiber length, content (5, 10, 15 and 20 wt%) and quality (poor, standard, good) were evaluated. Mechanical properties and structure of materials were examined using tensile testing, light and scanning electron microscopy. Hemp fiber reinforcement of gluten plastics significantly influenced the mechanical properties of the material. Short hemp fibers processed in a high speed grinder were more homogenously spread in the material than long unprocessed fibers. Fiber content in the material showed a significant positive correlation with tensile strength and Young's modulus, and a negative correlation with fracture strain and strain at maximum stress. Quality of the hemp fibers did not play any significant role for tensile strength and strain, but the Young's modulus was significantly and positively correlated with hemp fiber quality. Despite the use of short hemp fibers, the reinforced gluten material still showed uneven mechanical properties within the material, a result from clustering of the fibers and too poor bonding between fibers and gluten material. Both these problems have to be resolved before reinforcement of gluten plastics by industrial hemp fibers is applicable on an industrial scale.
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| 19. |
- Åkesson, Dan, 1970-, et al.
(författare)
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Mechanical Recycling of PLA Filled with a High Level of Cellulose Fibres
- 2016
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Ingår i: Journal of Polymers and the Environment. - : Springer. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 25:3, s. 185-195
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Tidskriftsartikel (refereegranskat)abstract
- Composites consisting of 30 vol% PLA and 70 vol% cellulose fibres were prepared with compression moulding. In the first part of the study, the recyclability of this composite material was investigated by grinding the material and using the recyclate obtained as a filler for PLA. Thus, the recyclate was compounded with PLA in loadings ranging from 20 to 50 wt%. The composites obtained were characterised by tensile tests, Charpy impact tests, DMTA, and SEM. Tests showed that the recyclate had a relatively good reinforcing effect. Stress at break increased from about 50 to 77 MPa and the modulus increased from 3.6 to 8.5 GPa. In the second part of the study, the ability to mechanically recycle the composites obtained was evaluated by repeated processing. Composite with two loadings of the recyclate (20 wt% and 50 %) was injection moulded repeatedly, six times. Tests showed that the composite material with 20 wt% recyclate could withstand six cycles relatively well, while the composite with the higher load degraded much more quickly. For the composites with 50 wt% recyclate, signs of polymer degradation could be seen already after reprocessing the composite once.
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