| 1. |
- Atari Jabarzadeh, Sevil, et al.
(författare)
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Use of essential oils for the prevention of biofilm formation on silicone rubber high voltage insulators
- 2015
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Ingår i: Polymers from Renewable Resources. - : Rapra Technology Ltd.. - 2041-2479 .- 2045-1377. ; 6:4, s. 119-136
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Tidskriftsartikel (refereegranskat)abstract
- The prevention of biofilm formation on high voltage insulators is important to avoid changes in the surface properties of the material and the subsequent failure of the application. Antimicrobial silicone rubber samples were prepared by the addition of thymol and eugenol to Sylgard 184 to determine the possibility of using natural antimicrobial agents present in essential oils in materials used for high voltage insulators. The antimicrobial effects of thymol and eugenol were studied for different fungal strains and for green algae identified in the biofilms formed on insulators in Tanzania, Sri Lanka and Sweden. It was successfully demonstrated that samples containing high amount of eugenol and different concentrations of thymol could inhibit the fungal growth of strains from Sri Lanka and Tanzania and the growth of green algae. The growth of strains from Sweden was also suppressed. The addition of eugenol to the material resulted in a noncrosslinked system and therefore, the antimicrobial effect of the additive in the material could not be assessed. The addition of thymol did not significantly influence the thermal and mechanical properties of Sylgard184. Although thermal analysis revealed that a large amount of the antimicrobial agent was lost during sample preparation, the materials were effective against microbial growth, even at low thymol concentrations.
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| 2. |
- Chen, Fei, et al.
(författare)
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Chitosan extrusion at high solids content : An orthogonal experimental design study
- 2014
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 5:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- For economic reasons and to save time there is a need to shorten the drying operation associated with the production of chitosan materials. Hence it is of interest to extrude chitosan at as high a solids content as possible. This is, to our knowledge, the first systematic study of the extrusion of chitosan at high solids content (60 wt%). An orthogonal experimental design was used to evaluate the effect of processing conditions and material factors on the extrudability of chitosan. This, together with the examination of the evenness and surface finish of the extrudate, made it possible to determine the best conditions for obtaining a readily extrudable high quality material. It was observed that a 1/1 ratio of chitosans with molar masses of 12 and 133 kDa, a process liquid containing 30 wt% acetic acid and 70 wt% water, and extrusion at 50 rpm and 50°C were the optimal material and processing conditions. Materials processed under these conditions were evaluated mechanically at different times after extrusion (stored at 50% RH) in order to see when the properties stabilized. Most mass loss occurred within the first three days after extrusion and this governed the mechanical properties (stiffness and extensibility), which also exhibited the largest changes within these three days (an increase in modulus from 18 to 830 MPa and a decrease in elongation at break from 17 to 3%).
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| 3. |
- Henrik Ullsten, N., et al.
(författare)
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Extruded high quality materials from wheat gluten
- 2010
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 1:4, s. 173-186
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report that the addition of ammonium hydroxide (NH4OH)significantly enhance the properties of extruded WG-based materials. The grainystructure disappeared and the extrudate became more uniform and glossy. Thebarrier properties improved and the oxygen permeability at dry conditions was aslow as that for a number of petroleum-based plastics (poly(ethylene terephthalateand polyamide 66). The protein structure in this material was extensivelyaggregated, which improved the strength and stiffness; there was a ca 4-foldincrease in maximum stress compared to that of the NH4OH-free samples. Theprotein solubility decreased to almost zero. Even a severe sonication treatmentin sodium dodecyl sulphate (SDS) did not increase the solubility. The only typeof protein that it was possible to extract was the 'thermo-resistant' w-gliadinslacking disulfide-bonds. Our result provides new opportunities to develop a WGbasedfilm extrudate for potential use as e.g. a renewable barrier layer in foodand non-food laminate packagings.
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| 4. |
- Kittikorn, Thorsak, et al.
(författare)
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The effect of surface modifications on the mechanical and thermal properties of empty fruit bunch oil palm fibre PP biocomposites
- 2012
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 3:3, s. 79-100
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the effect of chemical surface modifications on empty fruit bunch oil palm fibre/polypropylene composite properties. By FTIR spectra, propionylated fibre and PPgMA-modified fibre showed the presence of a carbonyl group of esters while vinyltrimethoxysilane-treated fibre showed a peak of silicate, confirming that the modifications were successful. PPgMAmodified fibre PP composite at fibre content 20% demonstrated the highest modulus of 0.71 GPa while the modulus of unmodified fibre PP composite was 0.56 GPa. By DSC analysis, PPgMA-modified fibre and vinyltrimethoxysilane-treated fibre PP composite at the same fibre content of 5% showed the highest crystallinity of 46% and 44% respectively whereas unmodified fibre PP composite showed a lower crystallinity of 38%. The DMTA analysis showed that after 60°C, the modified fibre PP composites exhibited a higher stiffness than pure polypropylene.
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| 5. |
- Köpcke, Viviana, et al.
(författare)
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Optimization of treatments for the conversion of eucalyptus kraft pulp to dissolving pulp
- 2010
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 1:1
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Tidskriftsartikel (refereegranskat)abstract
- Eucalyptus wood is known worldwide for its use in the production of kraft pulps and dissolving pulps. In our previous study, the feasibility of using a eucalyptus kraft pulp as a dissolving pulp was investigated. It was demonstrated that a kraft pulp subjected to a sequence of treatments that included enzymatic treatments using a xylanase and a monocomponent endoglucanase and, an alkali extraction, accomplished the requirements of a commercial dissolving pulp in terms of cellulose reactivity and hemicellulose content. Nevertheless, the low degree of polymerization and the presence of cellulose II showed that the combination of treatments had to be optimized. As a result, the parameters involved in the sequence of treatments were examined as well as their influence in the production of dissolving pulps. Furthermore, new sequences were tested. It was noticed that by decreasing the concentration of alkali in the alkali extraction stage, no cellulose II formed at short reaction times (10 min.) and that the degree of polymerization was increased. On the other hand, the cellulose reactivity and the hemicellulose content were barely affected. Moreover, a high pulp consistency (10%) led to an inhomogeneous mixture and the stirring effect was slightly noticeable.
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| 6. |
- Li, Dongfang, et al.
(författare)
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Treatment of a cellulose fiber surface with a suberin monomer-derived polymer
- 2015
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Ingår i: Polymers from Renewable Resources. - : Rapra Technology Ltd.. - 2041-2479 .- 2045-1377. ; 6:3, s. 75-90
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Tidskriftsartikel (refereegranskat)abstract
- The biorefinery concept requires the development of value-added products, such as materials from biomass, including bark. Suberin is the most abundant component in birch (Betula verrucosa) outer bark and acts as a barrier against the penetration of water and external attacks from microorganisms. The aliphatic domain of suberin is rich in hydroxy fatty acids, such as cis-9,10-epoxy-18- hydroxyoctadecanoic acid. In this study, it was isolated from the outer bark of birch and polymerized to prepare polyepoxy acid (PEA), which was used to impregnate filter papers. After complete drying, PEA-loaded filter papers were placed under UV to crosslink the epoxides through cationic polymerization with a diaryliodonium salt as the photo-initiator. The crosslinking was evaluated using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The materials obtained after UV curing showed substantially increased hydrophobicity, decreased moisture absorption, increased tensile strength, and increased ductility. Field-emission scanning electron microscopy (FE-SEM) showed that the crosslinked PEA covered the surface of the cellulose fibers and filled the interstitial spaces.
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| 7. |
- Nawaz, Sohail, et al.
(författare)
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Migration and chemical consumption of deltamethrin and piperonyl butoxide from polyethylene in aqueous media
- 2013
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 4:1, s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- Deltamethrin (DM), an important insecticide (synthetic pyrethroid) together with synergist piperonyl butoxide (PBO), is used for food storage and insect control purposes. It is often impregnated in polymers for controlled and effective release of insecticide. The migration and chemical consumption of DM and PBO from moulded polyethylene sheets was studied. The thermal behaviour of pristine DM and the prepared polyethylene compound was studied by differential scanning calorimetry. DM did not crystallize and remained in a liquid state after cooling to room temperature. Evaporation rates and activation energies of evaporation were determined by thermogravimetry for pristine DM, PBO, a solution of DM and PBO and for the PE compound. Evaporation from the DM/PBO solution was greater than that predicted from the evaporation rates of the individual compounds, which suggested that the DM/PBO solution obeyed non-ideal solution properties. The migration of DM and PBO from the polyethylene was studied in liquid water at 80 and 95 °C and in air of different relative humidities (60 and 80%) at 80 °C. Exposure to liquid water caused degradation and hydrolysis of the ester bond in DM, present in the prepared material, and generated species containing hydroxyl groups. Liquid chromatography and infrared spectroscopy showed a significant migration of the active species in liquid water, whereas the loss of DM and PBO in air at 80°C (60 and 80 %RH) was negligible over 30 days.
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| 8. |
- Ndazi, Bwire, et al.
(författare)
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Characterization of the potential of soda cooking to extract fibrous residues from rice hulls
- 2010
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 1:3, s. 143-160
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, the potential of soda cooking to extract fibrous residues from rice hulls was investigated. Soda cooking was carried out at 170oC for 60 minutes using 5 to 13% NaOH. The goal was to selectively degrade silica and lignin from the structure of the rice hulls and produce fibrous carbohydrates that could be used as fillers in polymer biocomposites. This was studied by characterizing the physical and chemical properties of the fibrous residues and the spent liquor products. Results of scanning electron microscopy have revealed a substantial fragmentation of rice hulls above 7.5% NaOH charge. The fragmentation was accompanied with a significant removal of silica and lignin and the reduction of fibrous residues yield to 57% at 13%NaOH. Wet chemical composition analyses, infrared spectroscopy and x-ray spectroscopy have also revealed that lignin and silica were partly retained in the fibrous residue while the carbohydrates content were not affected. It is therefore concluded that soda cooking could be among the best processes for dissolving lignin and silica from rice hulls if the cooking conditions are optimized
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| 9. |
- Salehi Movahed, Alireza, et al.
(författare)
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Effect of model lignin structures on the oxidation of unsaturated fatty acids
- 2010
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Ingår i: Polymers from Renewable Resources. - : SAGE Publications. - 2041-2479 .- 2045-1377. ; 1:2
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to better understand vegetable oils as raw materials in the application of wood protection in order to obtain improved durability of exterior wood materials in an environmentally friendly way. This was done by studying the effect of lignin model compounds on the auto-oxidation rate of methyl linoleate. The auto-oxidation process of methyl linoleate was measured by itself and in combination with 1 wt% phenolic and non-phenolic lignin model compounds at 70°C. The effect of lignin compounds on the methyl linoleate auto-oxidation process was monitored by 1H-NMR, size exclusion chromatography (SEC), and real-time infrared spectroscopy (RT-IR). It was observed that phenolic groups and radical conjugation are the main contributors to an antioxidant effect of lignin compounds on the oxidation rate of the methyl linoleate. Ferulic acid, which is phenolic and contains a carboxylic group, has the largest antioxidant effect on methyl linoleate. It was also found that the antioxidant effect existed, despite the low solubility of ferulic acid in methyl linoleate. This research demonstrates that it is possible to follow the auto-oxidation process in real time to uncover the effects of wood constituents on the fatty acid auto-oxidation process. Additionally, this knowledge that drying rate of oil can be tuned with the addition of lignin compounds can be used to predict drying times when this oil is applied to different species of wood.
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| 10. |
- Strömberg, Emma, et al.
(författare)
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Photo- and thermo-oxidation of polypropylene, recycled polypropylene and polylactide biocomposites in a microenvironment chamber
- 2010
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Ingår i: Polymers from Renewable Resources. - : iSmithers. - 2041-2479 .- 2045-1377. ; 1:1, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- This work presents and discusses the photo- and thermo-oxidation of some sustainable biocomposites based on biodegradable materials from renewable resources and virgin and recycled petroleum-based polymeric materials as matrix and reinforced with natural fibres. PP/wood fl our, recycled PP/cellulose and PLA/wood fl our composites were degraded by photo-oxidation in a microenvironment chamber, in parallel thermo-oxidation was performed in a forced-ventilation oven. Physical and chemical property changes were monitored by tensile testing, DSC, FTIR and SEM. Both PPW and recPPcell composites showed deterioration of the mechanical properties after 15 days of thermo-oxidation, indicating that the incorporated natural fi bres infl uenced the thermal stability of the whole composite. PLAW showed a smaller increase in crystallinity (13%) and a decrease in melt temperature than the corresponding neat PLA. The advantages of reinforcement of PLA by natural fi bres are shown by the dramatically improved thermal properties of PLAW compared to the neat polymer.
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