| 1. |
- Akbari, Samira, et al.
(författare)
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Novel Bio-based Branched Unsaturated Polyester Resins for High-Temperature Applications
- 2023
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Ingår i: Journal of Polymers and the Environment. - 1566-2543 .- 1572-8919.
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Tidskriftsartikel (refereegranskat)abstract
- Unsaturated polyester resins, one of the most important thermosets, are invariably produced from oil-based monomers. Their application is limited in areas where high thermal stability is required due to their low Tg. Besides, these resins contain 30–40% hazardous styrene as a reactive solvent. Therefore, developing bio-based solventless unsaturated polyester resin with medium to high thermomechanical properties compared to petrochemical-based counterparts is important. In order to achieve this, a series of branched bio-based unsaturated polyester resins were synthesized using bulk polymerization method in two steps. In the first step, four different intermediates were prepared by reacting glycerol (as a core molecule) with either isosorbide (diol), 1,3-propanediol (diol), 2,5-furandicarboxylic acid (saturated diacid), or adipic acid (saturated diacid). In the second step, the branched intermediate was end capped with methacrylic anhydride to introduce reactive sites for cross-linking on the branch ends. The chemical structure of the resins was characterized by 13C-NMR. FT-IR confirmed the polycondensation reaction in the first step and the end functionalization of the resins with methacrylic anhydride in the second step. The effect of 2,5-furandicarboxylic acid and isosorbide on thermomechanical and thermal properties was investigated using dynamic mechanical analysis, differential scanning calorimetry, and thermo-gravimetric analysis. Results indicated that 2,5-furandicarboxylic acid based resins had superior thermomechanical properties compared to a commercial reference unsaturated polyester resin, making them promising resins for high-temperature composite applications. For example, the resin based on 2,5-furandicarboxylic acid and isosorbide and the resin based on 2,5-furandicarboxylic acid and 1,3-propanediol gave glass transition temperatures of 173 °C and 148 °C, respectively. Although the synthesized 2,5-furandicarboxylic acid based resins had higher viscosity (22.7 Pas) than conventional unsaturated polyester (0.4–0.5 Pas) at room temperature, preheated resins can be used for making high-temperature-tolerance fiber-reinforced composite.
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| 2. |
- Asadollahzadeh, Mohammadtaghi, et al.
(författare)
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Application of Fungal Biomass for the Development of New Polylactic Acid-Based Biocomposites
- 2022
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 14:9
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Tidskriftsartikel (refereegranskat)abstract
- Fungal biomass (FB), a by-product of the fermentation processes produced in large volumes, is a promising biomaterial that can be incorporated into poly(lactic acid) (PLA) to develop enhanced biocomposites that fully comply with the biobased circular economy concept. The PLA/FB composites, with the addition of triethyl citrate (TEC) as a biobased plasticizer, were fabricated by a microcompounder at 150 °C followed by injection molding. The effects of FB (10 and 20 wt %) and TEC (5, 10, and 15 wt %) contents on the mechanical, thermal and surface properties of the biocomposites were analyzed by several techniques. The PLA/FB/TEC composites showed a rough surface in their fracture section. A progressive decrease in tensile strength and Young’s modulus was observed with increasing FB and TEC, while elongation at break and impact strength started to increase. The neat PLA and biocomposite containing 10% FB and 15% TEC exhibited the lowest (3.84%) and highest (224%) elongation at break, respectively. For all blends containing FB, the glass transition, crystallization and melting temperatures were shifted toward lower values compared to the neat PLA. The incorporation of FB to PLA thus offers the possibility to overcome one of the main drawbacks of PLA, which is brittleness.
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| 3. |
- Bakare, Fatimat O., et al.
(författare)
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Thermomechanical properties of bio-based composites made from a lactic acid thermoset resin and flax and flax/basalt fibre reinforcements
- 2016
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 83, s. 176-184
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Tidskriftsartikel (refereegranskat)abstract
- Low viscosity thermoset bio-based resin was synthesised from lactic acid, allyl alcohol and pentaerythritol. The resin was impregnated into cellulosic fibre reinforcement from flax and basalt and then compression moulded at elevated temperature to produce thermoset composites. The mechanical properties of composites were characterised by flexural, tensile and Charpy impact testing whereas the thermal properties were analysed by dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The results showed a decrease in mechanical properties with increase in fibre load after 40 wt.% for the neat flax composite due to insufficient fibre wetting and an increase in mechanical properties with increase fibre load up to 60 wt.% for the flax/basalt composite. The results of the ageing test showed that the mechanical properties of the composites deteriorate with ageing; however, the flax/basalt composite had better mechanical properties after ageing than the flax composite before ageing.
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| 4. |
- Bátori, Veronika, 1980-, et al.
(författare)
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Anaerobic degradation of bioplastics: A review
- 2018
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Ingår i: Waste Management. - : Elsevier BV. - 0956-053X. ; 80, s. 406-413
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW), leading to renewableenergy production in the form of methane, is a preferable method for dealing with the increasing amountof waste. Food waste is separated at the source in many countries for anaerobic digestion. However, thepresence of plastic bags is a major challenge for such processes. This study investigated the anaerobicdegradability of different bioplastics, aiming at potential use as collecting bags for the OFMSW. Thechemical composition of the bioplastics and the microbial community structure in the AD processaffected the biodegradation of the bioplastics. Some biopolymers can be degraded at hydraulic retentiontimes usually applied at the biogas plants, such as poly(hydroxyalkanoate)s, starch, cellulose and pectin,so no possible contamination would occur. In the future, updated standardization of collecting bags forthe OFMSW will be required to meet the requirements of effective operation of a biogas plant.
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| 5. |
- Bátori, Veronika, 1980-, et al.
(författare)
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Pectin-based Composites
- 2017
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Ingår i: Handbook of Composites from Renewable Materials. - : John Wiley & Sons. - 9781119223795 ; , s. 487-518
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- One third of the cell wall of vascular plants is composed of pectin, which serves as the cementing material for the cellulosic network, behaving as a stabilized gel. Industrially, pectin is produced from juice and sugar production waste. Different sources and extraction conditions result in diversity in characteristics and applications of pectin. Most commonly, pectin is used in the food industry as a gelling and thickening agent and it is favored in the pharmaceutical industry as a carrier for colon-specific drugs. Pectin has good potential to be utilized as a matrix in production of environmentally friendly film packaging as well as biocomposite materials. Pectin is sensitive to chemical reactions and promotes the homogeneous immobilization of cells, genes, and proteins. However, due to limited mechanical properties pectin is not used for structural applications but instead rather for composites in which its biodegradable properties can be utilized. Pectin is often reinforced with hydroxyapatite and biphasic calcium phosphate for bone regeneration and tissue engineering applications. It can also be used as a biosorbent for copper removal from aqueous solutions. Active packaging of nanohybrids composed of pectin and halloysite nanotubes that are loaded with rosemary essential oil is another application of pectin-based composites.
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| 6. |
- Bátori, Veronika, 1980-, et al.
(författare)
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Production of Pectin-Cellulose Biofilms: A New Approach for Citrus Waste Recycling
- 2017
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Ingår i: International Journal of Polymer Science. - : Hindawi Limited. - 1687-9422 .- 1687-9430. ; 2017, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- While citrus waste is abundantly generated, the disposal methods used today remain unsatisfactory: they can be deleterious for ruminants, can cause soil salinity, or are not economically feasible; yet citrus waste consists of various valuable polymers. This paper introduces a novel environmentally safe approach that utilizes citrus waste polymers as a biobased and biodegradable film, for example, for food packaging. Orange waste has been investigated for biofilm production, using the gelling ability of pectin and the strength of cellulosic fibres. A casting method was used to form a film from the previously washed, dried, and milled orange waste. Two film-drying methods, a laboratory oven and an incubator shaker, were compared. FE-SEM images confirmed a smoother film morphology when the incubator shaker was used for drying. The tensile strength of the films was 31.67 ± 4.21 and 34.76 ± 2.64 MPa, respectively, for the oven-dried and incubator-dried films, which is within the range of different commodity plastics. Additionally, biodegradability of the films was confirmed under anaerobic conditions. Films showed an opaque appearance with yellowish colour.
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| 7. |
- Bátori, Veronika, 1980-, et al.
(författare)
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The effect of glycerol, sugar and maleic anhydride on pectin-cellulose biofilms prepared from orange waste
- 2019
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Ingår i: Polymers. - : MDPI AG. - 2073-4360.
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Tidskriftsartikel (refereegranskat)abstract
- This study was conducted to improve the properties of thin films prepared from orange waste by the solution casting method. The main focus was the elimination of holes in the film structure by establishing better cohesion between the major cellulosic and pectin fractions. For this, a previously developed method was improved first by the addition of sugar to promote pectin gelling, then by the addition of maleic anhydride. Principally, maleic anhydride was introduced to the films to induce cross-linking within the film structure. The effects of concentrations of sugar and glycerol as plasticizers and maleic anhydride as a cross-linking agent on the film characteristics were studied. Maleic anhydride improved the structure, resulting in a uniform film, and morphology studies showed better adhesion between components. However, it did not act as a cross-linking agent, but rather as a compatibilizer. The middle level (0.78%) of maleic anhydride content resulted in the highest tensile strength (26.65 ± 3.20 MPa) at low (7%) glycerol and high (14%) sugar levels and the highest elongation (28.48% ± 4.34%) at high sugar and glycerol levels. To achieve a uniform film surface with no holes present, only the lowest (0.39%) level of maleic anhydride was necessary.
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| 8. |
- Esmaeili, Nima, et al.
(författare)
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Synthesis and characterization of methacrylated star-shaped poly(lactic acid) emplying core moilecules with different hydroxyl groups
- 2017
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 134:39
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Tidskriftsartikel (refereegranskat)abstract
- A set of novel bio-based star-shaped thermoset resins was synthesized via ring-opening polymerization of lactide and employing different multi-hydroxyl core molecules, including ethylene glycol, glycerol, and erythritol. The branches were end-functionalized with methacrylic anhydride. The effect of the core molecule on the melt viscosity, the curing behavior of the thermosets and also, the thermomechanical properties of the cured resins were investigated. Resins were characterized by Fourier-transform infrared spectroscopy, 13C-NMR, and 1H-NMR to confirm the chemical structure. Rheological analysis and differential scanning calorimetry analysis were performed to obtain the melt viscosity and the curing behavior of the studied star-shaped resins. Thermomechanical properties of the cured resins were also measured by dynamic mechanical analysis. The erythritol-based resin had superior thermomechanical properties compared to the other resins and also, lower melt viscosity compared to the glycerol-based resin. These are of desired characteristics for a resin, intended to be used as a matrix for the structural composites. Thermomechanical properties of the cured resins were also compared to a commercial unsaturated polyester resin and the experimental results indicated that erythritol-based resin with 82% bio-based content has superior thermomechanical properties, compared to the commercial polyester resin. Results of this study indicated that although core molecule with higher number of hydroxyl groups results in resins with better thermomechanical properties, number of hydroxyl groups is not the only governing factor for average molecular weight and melt viscosity of the uncured S-LA resins.
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| 9. |
- Fazelinejad, Samaneh, et al.
(författare)
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Repeated mechanical recycling of polylactic acid filled with chalk
- 2017
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Ingår i: Progress in Rubber, Plastics and Recycling Technology. - 0266-7320 .- 1478-2413. ; , s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Polylactic acid (PLA) was compounded with 30 wt% chalk and 5 wt% of a biobased plasticiser on a twin screw extruder. Mechanical recycling of the obtained compound was studied by multiple extrusions up to six cycles. The degradation was monitored by mechanical and thermal tests. Tensile and flexural tests did not reveal any major degradation after six cycles of processing. Characterising the material with differential scanning calorimetry (DSC) did not detect any significant change of the thermal properties. The material was also characterised by FTIR and, again, no significant change was detected. The material was finally characterised by melt flow index and by proton nuclear magnetic resonance (1H-NMR). Both tests revealed that some degradation had occurred. The 1H-NMR clearly showed that the chain length had been reduced. Also, the MFI test showed that degradation had occurred. However, the study reveals that PLA filled with chalk can be recycled by repeated extrusion for up to 6 cycles, without severe degradation. This should be of relevance when considering the end-of-life treatment of polymer products made from PLA.
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| 10. |
- Furgier, Valentin, et al.
(författare)
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Development and Characterisation of Composites Prepared from PHBV Compounded with Organic Waste Reinforcements, and Their Soil Biodegradation
- 2024
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Ingår i: Materials. - 1996-1944. ; 17:3
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Tidskriftsartikel (refereegranskat)abstract
- Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biobased and biodegradable polymer. This polymer is considered promising, but it is also rather expensive. The objective of this study was to compound PHBV with three different organic fillers considered waste: human hair waste (HHW), sawdust (SD) and chitin from shrimp shells. Thus, the cost of the biopolymer is reduced, and, at the same time, waste materials are valorised into something useful. The composites prepared were characterised by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile strength and scanning electron micrograph (SEM). Tests showed that chitin and HHW did not have a reinforcing effect on tensile strength while the SD increased the tensile strength at break to a certain degree. The biodegradation of the different composites was evaluated by a soil burial test for five months. The gravimetric test showed that neat PHBV was moderately degraded (about 5% weight loss) while reinforcing the polymer with organic waste clearly improved the biodegradation. The strongest biodegradation was achieved when the biopolymer was compounded with HHW (35% weight loss). The strong biodegradation of HHW was further demonstrated by characterisation by Fourier-transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR). Characterisation by SEM showed that the surfaces of the biodegraded samples were eroded.
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| 11. |
- Gomes Hastenreiter, Lara Lopes, et al.
(författare)
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Synthesis of Lactic Acid-Based Thermosetting Resins and Their Ageing and Biodegradability
- 2020
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; :12, s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- The present work is focused on the synthesis of bio-based thermoset polymers and their thermo–oxidative ageing and biodegradability. Toward this aim, bio-based thermoset resins with different chemical architectures were synthesized from lactic acid by direct condensation with ethylene glycol, glycerol and pentaerythritol. The resulting branched molecules with chain lengths (n) of three were then end-functionalized with methacrylic anhydride. The chemical structures of the synthesized lactic acid derivatives were confirmed by proton nuclear magnetic resonance spectroscopy (1H-NMR) and Fourier transform infrared spectroscopy (FT–IR) before curing. To evaluate the effects of structure on their properties, the samples were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and the tensile testing. The samples went through thermo-oxidative ageing and biodegradation; and their effects were investigated. FT-IR and 1H-NMR results showed that three different bio-based resins were synthesized using polycondensation and end-functionalization. Lactic acid derivatives showed great potential to be used as matrixes in polymer composites. The glass transition temperature of the cured resins ranged between 44 and 52 °C. Pentaerythritol/lactic acid cured resin had the highest tensile modulus and it was the most thermally stable among all three resins. Degradative processes during ageing of the samples lead to the changes in chemical structures and the variations in Young’s modulus. Microscopic images showed the macro-scale surface degradation on a soil burial test.
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| 12. |
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| 13. |
- Grundberg, E, et al.
(författare)
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Large-scale association study between two coding LRP5 gene polymorphisms and bone phenotypes and fractures in men
- 2007
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Ingår i: Osteoporosis International. - : Springer Science and Business Media LLC. - 0937-941X .- 1433-2965. ; 19:6, s. 829-837
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Tidskriftsartikel (refereegranskat)abstract
- Summary Herein we investigated the association between polymorphisms in the LRP5 gene and bone phenotypes and fractures in three large male cohorts based on the rationale that mutations in LRP5 cause severe bone phenotypes. Results showed an association of the Val667Met SNP with spine BMD in 3,800 young and elderly men. Introduction The low-density lipoprotein receptor-related protein 5 (LRP5)-Wnt signalling system is of importance for regulating osteoblastic activity, which became clear after findings that inactivating mutations in LRP5 cause osteoporosis. The overall aim of this study was to investigate the association between polymorphisms in the LRP5 gene and bone mineral density (BMD) in three large cohorts of young and elderly men. Methods The cohorts used were MrOS Sweden (n = 3014, aged 69–81 years) and MrOs Hong Kong (n = 2000, aged > 65 years) and the Swedish GOOD study (n = 1068, aged 18–20 years). The polymorphisms Val667Met and Ala1330Val were genotyped using a TaqMan assay. Results When combining the data from the Swedish cohorts in a meta-analysis (n = 3,800), men carrying the 667Met-allele had 3% lower BMD at lumbar spine compared with non-carriers (p < 0.05). The Val667Met SNP was not polymorphic in the Hong Kong population and thus were not included. There were no associations between the Ala1330Val SNP and bone phenotypes in the study populations. No associations between the LRP5 polymorphisms and self-reported fractures were seen in MrOs Sweden. Conclusions Results from these three large cohorts indicate that the Val667Met polymorphism but not the Ala1330Val contributes to the observed variability in BMD in the Swedish populations.
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| 14. |
- Gustafsson, Jesper, et al.
(författare)
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Development of Bio-Based Films and 3D Objects from Apple Pomace
- 2019
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- Extensive quantities of apple pomace are generated annually but its disposal is still challenging. This study addresses this issue by introducing a new, environmentally-friendly approach for the production of sustainable biomaterials from apple pomace, containing 55.47% free sugars and a water insoluble fraction, containing 29.42 ± 0.44% hemicelluloses, 38.99 ± 0.42% cellulose, and 22.94 ± 0.12% lignin. Solution casting and compression molding were applied to form bio-based films and 3D objects (i.e., fiberboards), respectively. Using glycerol as plasticizer resulted in highly compact films with high tensile strength and low elongation (16.49 ± 2.54 MPa and 10.78 ± 3.19%, respectively). In contrast, naturally occurring sugars in the apple pomace showed stronger plasticizing effect in the films and resulted in a fluffier and connected structure with significantly higher elongation (37.39 ± 10.38% and 55.41 ± 5.38%, respectively). Benefiting from the self-binding capacity of polysaccharides, fiberboards were prepared by compression molding at 100 °C using glycerol or naturally occurring sugars, such as plasticizer. The obtained fiberboards exhibited tensile strength of 3.02–5.79 MPa and elongation of 0.93%–1.56%. Possible applications for apple pomace biomaterials are edible/disposable tableware or food packaging.
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| 15. |
- Jabbari, Mostafa, et al.
(författare)
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Introducing all-polyamide composite coated fabrics : A method to produce fully recyclable single-polymer composite coated fabrics
- 2016
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 133:7
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Tidskriftsartikel (refereegranskat)abstract
- Novel all-polyamide composite (APC) has been developed to replace traditional coated fabrics with good interfacial adhesionand enhanced recyclability. The composite is fully recyclable since it contains no other materials except polyamide. APC was preparedby partially dissolving a polyamide fabric by treatment with a film-forming polyamide solution. The effect of the polyamidesolution concentration and gelling time on tensile and viscoelastic properties of APCs was investigated to explore the optimum processingparameters for balancing the good interfacial adhesion. The composite properties were studied by dynamic mechanical thermalanalysis (DMTA), tensile testing and scanning electron microscopy (SEM). The results showed a good adhesion between the coatingand the fabric. A new method was introduced to convert a low value added textile waste to a high value-added product. The compositeis tunable, in terms of having a dense or a porous top-layer depending on the end-use requirements.
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| 16. |
- Jabbari, Mostafa, et al.
(författare)
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New Solvent for Polyamide 66 and Its Use for Preparing a Single-Polymer Composite-Coated Fabric
- 2018
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Ingår i: International Journal of Polymer Science. - : Hindawi Limited. - 1687-9422 .- 1687-9430.
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Tidskriftsartikel (refereegranskat)abstract
- Polyamides (PAs) are one of the most important engineering polymers; however, the difficulty in dissolving them hinders their applications. Formic acid (FA) is the most common solvent for PAs, but it has industrial limitations. In this contribution, we proposed a new solvent system for PAs by replacing a portion of the FA with urea and calcium chloride (FAUCa). Urea imparts the hydrogen bonding and calcium ion from the calcium chloride, as a Lewis acid was added to the system to compensate for the pH decrease due to the addition of urea. The results showed that the proposed solvent (FAUCa) could readily dissolve PAs, resulting in a less decrease in the mechanical properties during the dissolution. The composite prepared using the FAUCa has almost the same properties as the one prepared using the FA solution. The solution was applied on a polyamide 66 fabric to make an all-polyamide composite-coated fabric, which then was characterized. The FAUCa solution had a higher viscosity than the one prepared using the neat FA solvent, which can be an advantage in the applications which need higher viscosity like preparing the all-polyamide composite-coated fabric. A more viscous solution makes a denser coating which will increase the water /gas tightness. In conclusion, using the FAUCa solvent has two merits: (1) replacement of 40% of the FA with less harmful and environmentally friendly chemicals and (2) enabling for the preparation of more viscous solutions, which makes a denser coating.
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| 17. |
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| 18. |
- Karasik, D., et al.
(författare)
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Disentangling the genetics of lean mass
- 2019
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Ingår i: American Journal of Clinical Nutrition. - : Elsevier BV. - 0002-9165 .- 1938-3207. ; 109:2, s. 276-287
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Tidskriftsartikel (refereegranskat)abstract
- Background: Lean body mass (LM) plays an important role in mobility and metabolic function. We previously identified five loci associated with LM adjusted for fat mass in kilograms. Such an adjustment may reduce the power to identify genetic signals having an association with both lean mass and fat mass. Objectives: To determine the impact of different fat mass adjustments on genetic architecture of LM and identify additional LM loci. Methods: We performed genome-wide association analyses for whole-body LM (20 cohorts of European ancestry with n = 38,292) measured using dual-energy X-ray absorptiometry) or bioelectrical impedance analysis, adjusted for sex, age, age(2), and height with or without fat mass adjustments (Model 1 no fat adjustment; Model 2 adjustment for fat mass as a percentage of body mass; Model 3 adjustment for fat mass in kilograms). Results: Seven single-nucleotide polymorphisms (SNPs) in separate loci, including one novel LM locus (TNRC6B), were successfully replicated in an additional 47,227 individuals from 29 cohorts. Based on the strengths of the associations in Model 1 vs Model 3, we divided the LM loci into those with an effect on both lean mass and fat mass in the same direction and refer to those as "sumo wrestler" loci (FTO and MC4R). In contrast, loci with an impact specifically on LMwere termed "body builder" loci (VCAN and ADAMTSL3). Using existing available genome-wide association study databases, LM increasing alleles of SNPs in sumo wrestler loci were associated with an adverse metabolic profile, whereas LM increasing alleles of SNPs in "body builder" loci were associated with metabolic protection. Conclusions: In conclusion, we identified one novel LM locus (TNRC6B). Our results suggest that a genetically determined increase in lean mass might exert either harmful or protective effects on metabolic traits, depending on its relation to fat mass.
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| 19. |
- Kopf, Sabrina, et al.
(författare)
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Effect of hydroxyapatite particle morphology on as-spun poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/hydroxyapatite composite fibers
- 2023
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Ingår i: Results in Materials. - : Elsevier BV. - 2590-048X. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxyapatite (HA) has shown very promising results in hard tissue engineering because of its similarity to bone and hence the capability to promote osteogenic differentiation. While the bioactivity of HA is uncontested, there are still uncertainties about the most suitable hydroxyapatite particle shapes and sizes for textile scaffolds. This study investigates the influence of the shape and size of HA particles on as spun fibers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and HA, their mechanical and thermal properties as well as their influence on the fiber degradation in simulated blood matrix and their capability to mineralize in simulated body fluid. The key findings were that the different HA particles’ size does not affect the melting temperature and still maintains a thermal stability suitable for fiber production. Tensile testing revealed decreased mechanical properties for PHBV/HA as spun fibers, independently of the particle morphology. However, HA particles with 30 nm in width and 100 nm in length at 1 wt% HA loading achieved the highest tenacity and elongation at break amongst all composite fibers with HA. Besides, the Ca/P ratio of their mineralization in simulated body fluid is the closest to the one of mineralized human bone, indicating the most promising bioactivity results of all HA particles studied.
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| 20. |
- Kopf, Sabrina, et al.
(författare)
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Textile Fiber Production of Biopolymers - A Review of Spinning Techniques for Polyhydroxyalkanoates in Biomedical Applications
- 2023
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Ingår i: Polymer reviews. - : Taylor & Francis. - 1558-3724 .- 1558-3716. ; , s. 200-245
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Forskningsöversikt (refereegranskat)abstract
- The superior biocompatibility and biodegradability of polyhydroxyalkanoates (PHAs) compared to man-made biopolymers such as polylactic acid promise huge potential in biomedical applications, especially tissue engineering (TE). Textile fiber-based TE scaffolds offer unique opportunities to imitate the anisotropic, hierarchical, or strain-stiffening properties of native tissues. A combination of PHAs' enhanced biocompatibility and fiber-based TE scaffolds could improve the performance of TE scaffolds. However, the PHAs' complex crystallization behavior and the resulting intricate spinning procedures remain a challenge. This review focuses on discussing the developments in PHA melt and wet spinning, their challenges, process parameters, and fiber characteristics while revealing the lack of an in-depth fiber characterization of wet-spun fibers compared to melt-spun filaments, leading to squandered potential in scaffold development. Additionally, the biomedical application of PHAs other than poly-4-hydroxybutyrate is hampered by a failure of polymer purity to meet the requirements for biomedical applications.
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| 21. |
- Kumar Ramamoorthy, Sunil, 1987-, et al.
(författare)
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Mechanical performance of biofibers and their corresponding composites
- 2019
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Ingår i: Mechanical and Physical Testing of Biocomposites, Fibre-Reinforced Composites and Hybrid Composites. - : Woodhead Publishing Limited.
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Bokkapitel (refereegranskat)abstract
- This chapter focuses on mechanical performance of biofibers such as flax, hemp, and sisal and their effect on mechanical performance when they are reinforced in thermoset and thermoplastic polymers. The aim of this chapter is to present an overview of the mechanical characterization of the biofibers and their corresponding composites. The mechanical characterization includes tensile, flexural, impact, compressive, shear, toughness, hardness, brittleness, ductility, creep, fatigue, and dynamic mechanical analyses. Detailed studies of each test have been widely reported and an overview is important to relate the studies. Studies pertaining to the topics are cited. The most common materials used in biocomposites are biofibers (also called natural fibers) and petroleum-based polymers such polypropylene. The use of renewable materials in biocomposites has increased in the past couple of decades owing to extensive research on cellulosic fibers and biopolymers based on starch or vegetable oil. Today, research is focused on reinforcing natural fibers in petroleum-based polymers. However, the emphasis is shifting toward the amount of renewable materials in biocomposites, which has led to the use of biopolymers instead of petroleum-based polymers in composites. The mechanical properties of some renewable resource-based composites are comparable to commercially available nonrenewable composites.Several plant biofibers have been reinforced in thermoplastics or thermosets to manufacture biocomposites because of their specific properties. The Young's modulus of commonly used biofibers such as hemp and flax could be over 50 GPa and therefore they could be good alternatives to glass fibers in several applications. The good mechanical properties of these biofibers influence the composites' mechanical performance when reinforced in polymers. It is important to understand the mechanical performance of these biofibers and biocomposites in a working environment. A detailed discussion about the mechanical performance of commonly used biofibers and composites is provided in this chapter.
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| 22. |
- Kumar Ramamoorthy, Sunil, 1987-, et al.
(författare)
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Waste Management Option for Bioplastics Alongside Conventional Plastics
- 2019
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Ingår i: IRC 2019 International Research Conference Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Bioplastics can be defined as polymers derived partly or completely from biomass. Bioplastics can be biodegradable such as polylactic acid (PLA) and polyhydroxyalkonoates (PHA); or non-biodegradable (biobased polyethylene (bio-PE), polypropylene (bio-PP), polyethylene terephthalate (bio-PET)). The usage of such bioplastics is expected to increase in the future due to new found interest in sustainable materials. At the same time, these plastics become a new type of waste in the recycling stream. Most countries do not have separate bioplastics collection for it to be recycled or composted. After a brief introduction of bioplastics such as PLA in UK, these plastics are once again replaced by conventional plastics by many establishments due to lack of commercial composting. Recycling companies fear the contamination of conventional plastic in the recycling stream and they said they would have to invest in expensive new equipment to separate bioplastics and recycle it separately. Bioplastics are seen as a threat to the recycling industry as bioplastics may degrade during the mechanical recycling process and the properties of the recycled plastics are seriously impacted. This project studies what happens when bioplastics contaminate conventional plastics.Three commonly used conventional plastics were selected for this study: polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET). In order to simulate contamination, two biopolymers, either polyhydroxyalkanoate (PHA) or thermoplastic starch (TPS) were blended with the conventional polymers. The amount of bioplastics in conventional plastics was either 1% or 5%. The blended plastics were processed again to see the effect of degradation. Mechanical, thermal and morphological properties of these plastics were characterized. The results from contamination showed that the tensile strength and the modulus of PE was almost unaffected whereas the elongation is clearly reduced indicating the increase in brittleness of the plastic. Generally, it can be said that PP is slightly more sensitive to the contamination than PE. This can be explained by the fact that the melting point of PP is higher than for PE and as a consequence, the biopolymer will degrade more quickly. However, the reduction of the tensile properties for PP is relatively modest. It is also important to notice that when plastics are recovered, there will always be a contamination that will reduce the material properties. The reduction of the tensile properties is not necessary larger than if a non-biodegradable polymer would have contaminated PE or PP. The Charpy impact strength is generally a more sensitive test method towards contamination. Again, PE is relatively unaffected by the contamination but for PP there is a relatively large reduction of the impact properties already at 1% contamination.PET is polyester and it is by its very nature more sensitive to degradation than PE and PP. PET also have a much higher melting point than PE and PP and as a consequence the biopolymer will quickly degrade at the processing temperature of PET. As for the tensile strength, PET can tolerate 1% contamination without any reduction of the tensile strength. However, when the impact strength is examined, it is clear that already at 1% contamination, there is a strong reduction of the properties. It can also be seen that presence of TPS is more detrimental to PET than PHA is. This can be explained by the fact that TPS contain reactive hydroxyl groups that can react with the ester bond of PET. This will in other words lead to degradation of PET.The thermal properties show the change in the crystallinity. As a general conclusion, it can be said that the plastics become less crystalline when contaminated. The blends were also characterized by SEM. Biphasic morphology can be seen as the two polymers are not truly blendable which also contributes to reduced mechanical properties. Recycling of the contaminated polymer shows an increase in crystallinity. This means that when the polymers are processed, polymer degradation occur causing the polymer chains to gradually become shorter which will enhance the crystallization process.The study shows that PE is relatively robust againt contamination, while polypropylene (PP) is somewhat more sensitive and polyethylene terephthalate (PET) can be quite sensitive towards contamination.
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| 23. |
- Ramamoorthy, Sunil Kumar, 1987-, et al.
(författare)
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Preparation and Characterization of Biobased Thermoset Polymers from Renewable Resources and Their Use in Composites
- 2017
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Ingår i: Handbook of Composites from Renewable Materials, Physico-Chemical and Mechanical Characterization. - Hoboken, New Jersey, USA : John Wiley & Sons. - 9781119223665 - 9781119224235 ; , s. 425-457, s. 425-457
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Bokkapitel (refereegranskat)abstract
- This chapter focuses on physicochemical and mechanical characterization of compositesmade from renewable materials. Most common renewable materials used in composites arenatural fibers and polymers based on starch or vegetable oil. The extent of using renewablematerials in biocomposites has increased during the past decade due to extensive research oncellulosic fibers and biobased polymers. Earlier, the research was focused on using the naturalfibers as reinforcement in crude oil-based polymers such as polypropylene. Later, the emphasisshifted to increase the amount of renewable components in the biocomposites which led tothe introductionof biobased resins in the composites. The properties of some biocompositesare today comparable to the properties for commercially available nonrenewable composites.Several plant biofibers have been used as reinforcement in biobased thermoplastics or thermosetsto manufacture biocomposites. Material characterization is important to understand theperformance of these composites under specific environment. Detailed discussion about themechanical and physicochemical characterization is provided in this chapter. Physicochemicalcharacterization includes chemical composition, density, viscosity, molecular weight, meltingtemperature, crystallinity,morphology, wettability, surface tension, water binding capacity,electricalconductivity, flammability, thermal stability, and swelling. Mechanical characterizationincludes tensile, flexural, impact, compressive, shear, toughness, hardness, brittleness, ductility,creep, fatigue, and dynamic mechanical analysis.
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| 24. |
- Sain, Sunanda, et al.
(författare)
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Hydrophobic Shape-Memory Biocomposites from Tung-Oil-Based Bioresin and Onion-Skin-Derived Nanocellulose Networks
- 2020
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- The fabrication of smart biocomposites from sustainable resources that could replace today’s petroleum-derived polymer materials is a growing field of research. Here, we report preparation of novel biocomposites using nanocellulose networks extracted from food residue (onion skin) and a vegetable oil-based bioresin. The resin was synthesized via the Diels-Alder reaction between furfuryl methacrylate and tung oil at various ratios of the components. The onion-skin-extracted cellulose nanofiber and cellulose nanocrystal networks were then impregnated with the resins yielding biocomposites that exhibited improved mechanical strength and higher storage modulus values. The properties of the resins, as well as biocomposites, were affected by the resin compositions. A 190-240-fold increase in mechanical strength was observed in the cellulose nanofiber (CNF) and cellulose nanocrystal (CNC)-reinforced biocomposites with low furfuryl methacrylate content. The biocomposites exhibited interesting shape-memory behavior with 80-96% shape recovery being observed after 7 creep cycles.
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| 25. |
- Sain, Sunanda, et al.
(författare)
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Synthesis and Properties of Thermosets from Tung Oil and Furfuryl Methacrylate
- 2020
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Ingår i: Polymers. - : MDPI. - 2073-4360. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- This work focuses on the development of cross-linked polymer from a highly unsaturated vegetable oil, tung oil (TO) and a bio-based acrylate, furfuryl methacrylate (FMA). The presence of a high degree of unsaturated carbon-carbon bonding in TO makes it a suitable precursor for polymer synthesis. Using this advantage of TO, in this work, we have synthesised a cross-linked polymer from TO and FMA through free radical polymerisation followed by Diels-Alder (DA) reaction. Successful incorporation of both of the raw materials and the two chemical reactions was shown using Fourier-transform infrared (FTIR) and Raman spectroscopy. The development of cross-linked structure was analysed through thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA).
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| 26. |
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| 27. |
- Svensson, Sofie, et al.
(författare)
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Reprocessing of High-Density Polyethylene Reinforced with Carbon Nanotubes
- 2020
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Ingår i: Journal of Polymers and the Environment. - : Springer. - 1566-2543 .- 1572-8919. ; 28:7, s. 1967-1973
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Tidskriftsartikel (refereegranskat)abstract
- High-density polyethylene (HDPE) was compounded with 3 wt% carbon nanotubes (CNTs). In order to simulate mechanical recycling, both the nanocomposite and neat HDPE were repeatedly extruded and subsequently analysed by tensile tests, Charpy impact strength, differential scanning calorimetry (DSC), oxidation induction time (OIT), Gel Performance Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR) and TEM After 10 cycles of extrusion, thermal, mechanical, and rheological tests did not reveal any significant degradation. In order to better study the effect of the CNTs, a large number of cycles were simulated by processing the materials for up to 200 min. After 200 min of processing, the neat HDPE was significantly degraded whereas the nanocomposite was almost unaffected.
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| 28. |
- Vandenput, L., et al.
(författare)
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A meta-analysis of previous falls and subsequent fracture risk in cohort studies
- 2024
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Ingår i: Osteoporosis International. - : Springer Nature. - 0937-941X .- 1433-2965. ; 35:3, s. 469-494
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Tidskriftsartikel (refereegranskat)abstract
- Summary: The relationship between self-reported falls and fracture risk was estimated in an international meta-analysis of individual-level data from 46 prospective cohorts. Previous falls were associated with an increased fracture risk in women and men and should be considered as an additional risk factor in the FRAX® algorithm. Introduction: Previous falls are a well-documented risk factor for subsequent fracture but have not yet been incorporated into the FRAX algorithm. The aim of this study was to evaluate, in an international meta-analysis, the association between previous falls and subsequent fracture risk and its relation to sex, age, duration of follow-up, and bone mineral density (BMD). Methods: The resource comprised 906,359 women and men (66.9% female) from 46 prospective cohorts. Previous falls were uniformly defined as any fall occurring during the previous year in 43 cohorts; the remaining three cohorts had a different question construct. The association between previous falls and fracture risk (any clinical fracture, osteoporotic fracture, major osteoporotic fracture, and hip fracture) was examined using an extension of the Poisson regression model in each cohort and each sex, followed by random-effects meta-analyses of the weighted beta coefficients. Results: Falls in the past year were reported in 21.4% of individuals. During a follow-up of 9,102,207 person-years, 87,352 fractures occurred of which 19,509 were hip fractures. A previous fall was associated with a significantly increased risk of any clinical fracture both in women (hazard ratio (HR) 1.42, 95% confidence interval (CI) 1.33–1.51) and men (HR 1.53, 95% CI 1.41–1.67). The HRs were of similar magnitude for osteoporotic, major osteoporotic fracture, and hip fracture. Sex significantly modified the association between previous fall and fracture risk, with predictive values being higher in men than in women (e.g., for major osteoporotic fracture, HR 1.53 (95% CI 1.27–1.84) in men vs. HR 1.32 (95% CI 1.20–1.45) in women, P for interaction = 0.013). The HRs associated with previous falls decreased with age in women and with duration of follow-up in men and women for most fracture outcomes. There was no evidence of an interaction between falls and BMD for fracture risk. Subsequent risk for a major osteoporotic fracture increased with each additional previous fall in women and men. Conclusions: A previous self-reported fall confers an increased risk of fracture that is largely independent of BMD. Previous falls should be considered as an additional risk factor in future iterations of FRAX to improve fracture risk prediction.
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| 29. |
- Vandenput, Liesbeth, et al.
(författare)
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A meta-analysis of previous falls and subsequent fracture risk in cohort studies
- 2024
-
Ingår i: Osteoporosis International. - : Springer. - 0937-941X .- 1433-2965. ; 35:3, s. 469-494
-
Tidskriftsartikel (refereegranskat)abstract
- SummaryThe relationship between self-reported falls and fracture risk was estimated in an international meta-analysis of individual-level data from 46 prospective cohorts. Previous falls were associated with an increased fracture risk in women and men and should be considered as an additional risk factor in the FRAX® algorithm.IntroductionPrevious falls are a well-documented risk factor for subsequent fracture but have not yet been incorporated into the FRAX algorithm. The aim of this study was to evaluate, in an international meta-analysis, the association between previous falls and subsequent fracture risk and its relation to sex, age, duration of follow-up, and bone mineral density (BMD).MethodsThe resource comprised 906,359 women and men (66.9% female) from 46 prospective cohorts. Previous falls were uniformly defined as any fall occurring during the previous year in 43 cohorts; the remaining three cohorts had a different question construct. The association between previous falls and fracture risk (any clinical fracture, osteoporotic fracture, major osteoporotic fracture, and hip fracture) was examined using an extension of the Poisson regression model in each cohort and each sex, followed by random-effects meta-analyses of the weighted beta coefficients.ResultsFalls in the past year were reported in 21.4% of individuals. During a follow-up of 9,102,207 person-years, 87,352 fractures occurred of which 19,509 were hip fractures. A previous fall was associated with a significantly increased risk of any clinical fracture both in women (hazard ratio (HR) 1.42, 95% confidence interval (CI) 1.33–1.51) and men (HR 1.53, 95% CI 1.41–1.67). The HRs were of similar magnitude for osteoporotic, major osteoporotic fracture, and hip fracture. Sex significantly modified the association between previous fall and fracture risk, with predictive values being higher in men than in women (e.g., for major osteoporotic fracture, HR 1.53 (95% CI 1.27–1.84) in men vs. HR 1.32 (95% CI 1.20–1.45) in women, P for interaction = 0.013). The HRs associated with previous falls decreased with age in women and with duration of follow-up in men and women for most fracture outcomes. There was no evidence of an interaction between falls and BMD for fracture risk. Subsequent risk for a major osteoporotic fracture increased with each additional previous fall in women and men.ConclusionsA previous self-reported fall confers an increased risk of fracture that is largely independent of BMD. Previous falls should be considered as an additional risk factor in future iterations of FRAX to improve fracture risk prediction.
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| 30. |
- Vandenput, Liesbeth, 1974, et al.
(författare)
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Update of the fracture risk prediction tool FRAX : a systematic review of potential cohorts and analysis plan
- 2022
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Ingår i: Osteoporosis International. - : Springer. - 0937-941X .- 1433-2965. ; 33:10, s. 2103-2136
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Forskningsöversikt (refereegranskat)abstract
- Summary: We describe the collection of cohorts together with the analysis plan for an update of the fracture risk prediction tool FRAX with respect to current and novel risk factors. The resource comprises 2,138,428 participants with a follow-up of approximately 20 million person-years and 116,117 documented incident major osteoporotic fractures.Introduction: The availability of the fracture risk assessment tool FRAX® has substantially enhanced the targeting of treatment to those at high risk of fracture with FRAX now incorporated into more than 100 clinical osteoporosis guidelines worldwide. The aim of this study is to determine whether the current algorithms can be further optimised with respect to current and novel risk factors.Methods: A computerised literature search was performed in PubMed from inception until May 17, 2019, to identify eligible cohorts for updating the FRAX coefficients. Additionally, we searched the abstracts of conference proceedings of the American Society for Bone and Mineral Research, European Calcified Tissue Society and World Congress of Osteoporosis. Prospective cohort studies with data on baseline clinical risk factors and incident fractures were eligible.Results: Of the 836 records retrieved, 53 were selected for full-text assessment after screening on title and abstract. Twelve cohorts were deemed eligible and of these, 4 novel cohorts were identified. These cohorts, together with 60 previously identified cohorts, will provide the resource for constructing an updated version of FRAX comprising 2,138,428 participants with a follow-up of approximately 20 million person-years and 116,117 documented incident major osteoporotic fractures. For each known and candidate risk factor, multivariate hazard functions for hip fracture, major osteoporotic fracture and death will be tested using extended Poisson regression. Sex- and/or ethnicity-specific differences in the weights of the risk factors will be investigated. After meta-analyses of the cohort-specific beta coefficients for each risk factor, models comprising 10-year probability of hip and major osteoporotic fracture, with or without femoral neck bone mineral density, will be computed.Conclusions: These assembled cohorts and described models will provide the framework for an updated FRAX tool enabling enhanced assessment of fracture risk (PROSPERO (CRD42021227266)).
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| 31. |
- Vu, Hoang Danh, et al.
(författare)
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Application of Immersed Membrane Bioreactor for Semi-Continuous Production of Polyhydroxyalkanoates from Organic Waste-Based Volatile Fatty Acids
- 2023
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Ingår i: Membranes. - : MDPI. - 2077-0375. ; 13:6
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Tidskriftsartikel (refereegranskat)abstract
- Volatile fatty acids (VFAs) appear to be an economical carbon feedstock for the cost-effective production of polyhydroxyalkanoates (PHAs). The use of VFAs, however, could impose a drawback of substrate inhibition at high concentrations, resulting in low microbial PHA productivity in batch cultivations. In this regard, retaining high cell density using immersed membrane bioreactor (iMBR) in a (semi-) continuous process could enhance production yields. In this study, an iMBR with a flat-sheet membrane was applied for semi-continuous cultivation and recovery of Cupriavidus necator in a bench-scale bioreactor using VFAs as the sole carbon source. The cultivation was prolonged up to 128 h under an interval feed of 5 g/L VFAs at a dilution rate of 0.15 (d−1), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. Potato liquor and apple pomace-based VFAs with a total concentration of 8.8 g/L were also successfully used in the iMBR, rendering the highest PHA content of 1.3 g/L after 128 h of cultivation. The PHAs obtained from both synthetic and real VFA effluents were affirmed to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a crystallinity degree of 23.8 and 9.6%, respectively. The application of iMBR could open an opportunity for semi-continuous production of PHA, increasing the feasibility of upscaling PHA production using waste-based VFAs.
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| 32. |
- Vu, Hoang Danh, et al.
(författare)
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Polyhydroxybutyrate-Natural Fiber Reinforcement Biocomposite Production and Their Biological Recyclability through Anaerobic Digestion
- 2022
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 15:23
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Tidskriftsartikel (refereegranskat)abstract
- The existing recycling methods of PHA-based material are ineffective in terms of increasing resource efficiency and the production of high value end-of-life products. Therefore, in this study, a novel approach of acidogenic fermentation was proposed to recycle PHB-based composites reinforced with natural fibers such as cellulose, chitin, chitosan, orange waste, sawdust, soy protein, and starch. The inclusion of cellulose, chitosan, and sawdust improved the impact properties of the composites while other fillers had various effects on the mechanical properties. These three composites and neat PHB were subsequently subjected to biological degradation via acidogenic digestion to determine the possibility of converting PHB-based composites into volatile fatty acids (VFAs). Two different pH levels of 6 and 10 were applied to assess the effect of pH on the bioconversion and inhibition of the methanogenesis. The results showed promising PHB degradation, contributing to considerable VFA production of 2.5 g/L at pH 6 after 47 days. At pH 6, the presence of the natural fibers in the biocomposites promoted the degradation rate. On the contrary, pH 10 proved to be more suitable for the degradation of the fibers. The VFA which is produced can be recirculated into PHB production, fitting with the concept of a circulating bioeconomy.
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| 33. |
- Vu, Hoang Danh, et al.
(författare)
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Production of polyhydroxyalkanoates (PHAs) by Bacillus megaterium using food waste acidogenic fermentation-derived volatile fatty acids
- 2021
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Ingår i: Bioengineered. - : Taylor & Francis Group. - 2165-5979 .- 2165-5987. ; 12:1, s. 2480-2498
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Tidskriftsartikel (refereegranskat)abstract
- High production costs still hamper fast expansion of commercial production of polyhydroxyalkanoates (PHAs). This problem is greatly related to the cultivation medium which accounts for up to 50% of the whole process costs. The aim of this research work was to evaluate the potential of using volatile fatty acids (VFAs), derived from acidogenic fermentation of food waste, as inexpensive carbon sources for the production of PHAs through bacterial cultivation. Bacillus megaterium could assimilate glucose, acetic acid, butyric acid, and caproic acid as single carbon sources in synthetic medium with maximum PHAs production yields of 9–11%, on a cell dry weight basis. Single carbon sources were then replaced by a mixture of synthetic VFAs and by a VFAs-rich stream from the acidogenic fermentation of food waste. After 72 h of cultivation, the VFAs were almost fully consumed by the bacterium in both media and PHAs production yields of 9–10%, on cell dry weight basis, were obtained. The usage of VFAs mixture was found to be beneficial for the bacterial growth that tackled the inhibition of propionic acid, iso-butyric acid, and valeric acid when these volatile fatty acids were used as single carbon sources. The extracted PHAs were revealed to be polyhydroxybutyrate (PHB) by characterization methods of Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The obtained results proved the possibility of using VFAs from acidogenic fermentation of food waste as a cheap substrate to reduce the cost of PHAs production.
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| 34. |
- Vu, Hoang Danh, et al.
(författare)
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Recycling strategies for polyhydroxyalkanoate-based waste materials : An overview.
- 2020
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 298
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Tidskriftsartikel (refereegranskat)abstract
- The plastics market is dominated by fossil-based polymers, but their gradual replacement by bioplastics (e.g., polyhydroxyalkanoates) is occurring. However, recycling strategies need to be developed to truly unveil the impact of bioplastics on waste accumulation. This review provides a state of the art of recycling strategies investigated for polyhydroxyalkanoate-based polymers and proposes future research avenues. Research on mechanical and chemical recycling is dominated by the use of extrusion and pyrolysis, respectively, while that on biodegradation of polyhydroxyalkanoates is related to soil and aquatic samples, and to anaerobic digestion towards biogas production. Research gaps exist in the relationships between polymer composition and ease of use of all recycling strategies investigated. This is of utmost importance since it will influence the need for separation at the source. Therefore, research emphasis needs to be given to the area to follow the continuous improvement of the process economics towards widespread commercial production of polyhydroxyalkanoates.
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| 35. |
- Vu, Hoang Danh, et al.
(författare)
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Thorough Investigation of the Effects of Cultivation Factors on Polyhydroalkanoates (PHAs) Production by Cupriavidus necator from Food Waste-Derived Volatile Fatty Acids
- 2022
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Ingår i: Fermentation. - : MDPI. - 2311-5637. ; 8:11
-
Tidskriftsartikel (refereegranskat)abstract
- Volatile fatty acids (VFAs) have become promising candidates for replacing the conventional expensive carbon sources used to produce polyhydroxyalkanoates (PHAs). Considering the inhibitory effect of VFAs at high concentrations and the influence of VFA mixture composition on bacterial growth and PHA production, a thorough investigation of different cultivation parameters such as VFA concentrations and composition (synthetic and waste-derived VFAs) media, pH, aeration, C/N ratio, and type of nitrogen sources was conducted. Besides common VFAs of acetic, butyric and propionic acids, Cupriavidus necator showed good capability for assimilating longer-chained carboxylate compounds of valeric, isovaleric, isobutyric and caproic acids in feasible concentrations of 2.5–5 g/L. A combination of pH control at 7.0, C/N of 6, and aeration of 1 vvm was found to be the optimal condition for the bacterial growth, yielding a maximum PHA accumulation and PHA yield on biomass of 1.5 g/L and 56%, respectively, regardless of the nitrogen sources. The accumulated PHA was found to be poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with the percentage of hydroxybutyrate in the range 91–96%. Any limitation in the cultivation factors was found to enhance the PHA yield, the promotion of which was a consequence of the reduction in biomass production.
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| 36. |
- Vu, Hoang Danh
(författare)
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Volatile Fatty Acids as a Key to Sustainability and Circularity in Polyhydroxyalkanoates Production
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The negative consequences of plastic pollution on both environmental and socio-economic aspects have motivated the development of sustainable and renewable materials to replace the petroleum-based plastic. Polyhydroxyalkanoates (PHAs), which are bioplastics, having an outstanding biodegradability and rather comparable thermal and mechanical properties, are potential alternatives for the replacement of conventional plastics. However, one of the hurdles on the way to PHA commercial production is the cost of conventional feedstock, which can constitute up to 50% of the production cost. In this regard, volatile fatty acids (VFAs) derived from acidogenic fermentation of organic waste can be a promising substrate to increase the cost-competitiveness of PHA production. Therefore, in this thesis, VFAs were utilized and developed to be a key carbon feedstock for the sustainable and economically feasible production of PHAs. The applicability of individual and mixed VFAs as potential substrates was initially investigated through the cultivation of two different PHA-bearing bacteria of Bacillus megaterium and Cupriavidus necator, providing an average PHA yield on biomass of 10 and 55%, respectively. Further thorough studies, in terms of VFAs loading and inhibition thresholds and operating parameters, were conducted to improve the conversion efficiency of VFAs by C. necator. Consequently, a biomass yield on VFAs of up to 82% was obtained, rendering a PHA accumulation of 1 g/L using actual waste derived VFA effluent. In addition, in order to tackle the inherent issue of low productivity in batch and/or fed-batch cultivations under high VFA containing feed, a novel approach of immersed membrane reactor (iMBR) was introduced and applied in this thesis. With the assistance of membrane filtration, the PHA production was conducted in semi-continuous mode (up to 128 h), yielding a maximum biomass and PHA production of 6.6 and 2.8 g/L, respectively. The outcomes achieved, furthermore, were 32.1 and 28.5%, respectively, higher than that from a continuous stirred tank (CSTR), in which the cultivation was affected by the washout effect. Moreover, considering the insufficiency of the current recycling methods of PHA-based products in terms of resource recovery, a novel attempt of acidogenic fermentation has been conducted to valorize the PHA-based composites through conversion into precursor VFAs. Afterwards, the recovered VFAs could be recirculated into PHA production, fulfilling the concept of a circular bioeconomy.
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| 37. |
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| 38. |
- Zillikens, M. C., et al.
(författare)
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Large meta-analysis of genome-wide association studies identifies five loci for lean body mass
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Lean body mass, consisting mostly of skeletal muscle, is important for healthy aging. We performed a genome-wide association study for whole body (20 cohorts of European ancestry with n = 38,292) and appendicular (arms and legs) lean body mass (n = 28,330) measured using dual energy X-ray absorptiometry or bioelectrical impedance analysis, adjusted for sex, age, height, and fat mass. Twenty-one single-nucleotide polymorphisms were significantly associated with lean body mass either genome wide (p < 5 x 10(-8)) or suggestively genome wide (p < 2.3 x 10(-6)). Replication in 63,475 (47,227 of European ancestry) individuals from 33 cohorts for whole body lean body mass and in 45,090 (42,360 of European ancestry) subjects from 25 cohorts for appendicular lean body mass was successful for five single-nucleotide polymorphisms in/ near HSD17B11, VCAN, ADAMTSL3, IRS1, and FTO for total lean body mass and for three single-nucleotide polymorphisms in/ near VCAN, ADAMTSL3, and IRS1 for appendicular lean body mass. Our findings provide new insight into the genetics of lean body mass.
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| 39. |
- Åkesson, Dan, 1970-, et al.
(författare)
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Effect of a Small Amount of Thermoplastic Starch Blend on the Mechanical Recycling of Conventional Plastics
- 2021
-
Ingår i: Journal of Polymers and the Environment. - : Springer. - 1566-2543 .- 1572-8919. ; 29, s. 985-991
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Tidskriftsartikel (refereegranskat)abstract
- The usage of bioplastics could increase in the future which may cause contamination of the waste streams of conventional plastics. The objective of this study was to investigate if a small amount of biopolymer contaminating conventional polymers would significantly affect mechanical and thermal properties. A starch-based plastic was first compounded by blending plasticised starch with PLA (polylactic acid). This polymer blend was subsequently compounded with HDPE (high density polyethylene), PP (polypropylene) or PET (polyethylene terephthalate) at 0%, 1% and 5% of the biopolymer. The compounds were characterised by tensile tests, Charpy impact tests, DSC (differential scanning calorimetry) and FESEM (field emission scanning electron microscopy). Tests showed that PE and PP were not significantly affected in terms of tensile strength and modulus but the elongation at break showed a strong reduction. PET was, on the other hand, incompatible with the starch-based plastic. Already at 1% contamination, PET had lost most of its impact strength. © 2020, The Author(s).
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| 40. |
- 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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| 41. |
- Åkesson, Dan, 1970-, et al.
(författare)
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Mechanical recycling of polylactic acid composites reinforced with wood fibres by multiple extrusion and hydrothermal ageing
- 2016
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Ingår i: Journal of reinforced plastics and composites (Print). - : Sage Publications. - 0731-6844 .- 1530-7964. ; 35:16, s. 1248-1259
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical recycling of polylactic acid composites reinforced with wood fibres was studied by multiple extrusions. The composite material was extruded seven times, and the mechanical and thermal properties were monitored by tensile tests, flexural tests, differential scanning calorimetry, Fourier-transform infrared and scanning electron microscopy. The results showed that the material retained its mechanical properties relatively well, for up to five cycles after which the tensile strength decreased by 23%. Thermal characterisation further showed that the glass transition temperature ( Tg) shifted several degrees centigrade towards lower temperatures, further indicating degradation of the polylactic acid polymer. Characterisation was also done on composite material, which was aged hydrothermally between each extrusion cycle in order to simulate post-consumer recycling of composite products, which had been exposed to water. Samples were aged at 50℃ in distilled water for 5 days. The thermal and mechanical testing showed that the material survived the ageing test fairly well.
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| 42. |
- Åkesson, Dan, 1970-
(författare)
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Mekanisk återvinning av biopolymerer och deras blandningar och kompositer
- 2015
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Annan publikation (populärvet., debatt m.m.)abstract
- Mekanisk återvinning av biopolymerer och deras blandningar och kompositerBiopolymerer blir allt vanligare på marknaden. Det är därför viktigt att utveckla återvinningssystem för att ta hand om dessa nya plaster. I ett pågående projekt, ’Hållbar återvinning av ”gröna” plaster och industriellt avfall’ studeras mekanisk återvinning av bioplaster. Återvinning av polymjölksyra (PLA) samt blandningar och kompositer av PLA har studerats genom upprepad bearbetning. Delar av dessa resultat kommer att presenteras.
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| 43. |
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| 44. |
- Åkesson, Dan, 1970-, et al.
(författare)
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Recycling of L-Poly-(lactide)-Poly-(butylene-succinate)-flax biocomposite
- 2016
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Ingår i: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 128, s. 77-88
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Tidskriftsartikel (refereegranskat)abstract
- The development of new plant fibre composites is a key point in the development of semi-structural biodegradable or biobased parts, especially for automotive applications. The aim of this original and innovating work is to study, at different scales, the recycling ability of a fully biodegradable L-Poly-(lactide)-Poly-(butylene-succinate)-flax (PLLA-PBS-flax) biocomposite. The biocomposites were manufactured by twin-screw extrusion followed by injection moulding, then the recycling behaviour was studied during successive injection moulding cycles. Firstly, we investigated the length of the flax fibre after compounding and injection, as well as the cell wall stiffness and hardness, by in-situ nanoindentation tests. Secondly, we focused on the effects of recycling on thermal, rheological and tensile properties. We highlighted a severe evolution of the cell wall properties, especially concerning the polysaccharidic matrix after the first thermal cycle, nanoindentation properties remaining quasi-stable after this first drop. Furthermore, the biocomposites did not show any significant evolution of their mechanical performances during cycle three or four of the first injection cycles; after this plateau, the tensile strength and strain as well as impact energy were significantly altered due to the conjugated fibre length decrease and degradation of the PLLA, the latter being emphasized when the flax fibre is embedded. Nevertheless, this fully biodegradable composite exhibits a suitable recycling behaviour for 3 or 4 cycles, which is sufficient for industrial applications.
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| 45. |
- Åkesson, Dan, 1970-, et al.
(författare)
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Recycling of wood fiber-reinforced HDPE by multiple reprocessing
- 2016
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Ingår i: Journal of Applied Polymer Science. - : John Wiley & Sons. - 0021-8995 .- 1097-4628. ; 133:35
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical recycling of high-density polyethylene (HDPE) reinforced with wood fiber was studied by means of repeated injection moulding. The change in properties during the recycling was monitored by tensile and flexural tests, Charpy impact tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), FTIR spectroscopy, and by measuring the fiber lengths. Tests were also done where injection moulding was combined with subsequent accelerated thermo-oxidative ageing and thereafter repeated numerous times. The results showed that the HDPE composites were relatively stable toward both the ageing conditions and the repeated injection moulding. The change of the mechanical properties was mainly observed as an increased elongation at max. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43877. © 2016 Wiley Periodicals, Inc.
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| 46. |
- Åkesson, Dan, 1970
(författare)
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Renewable Composites Prepared from Biobased Thermoset Resins
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In our efforts to create a more sustainable society, several researchers have tried to prepare composites from renewable materials in recent years. The use of natural fibres for reinforcement of composites has been relatively well studied. To date, most studies of natural fibre-reinforced composites have either involved the use of conventional thermoset resins or thermoplastic biopolymers. While there are currently several thermoplastic polymers on the market that are produced from renewable resources, thermosets are inevitably produced from petroleum resources. The development of biobased thermoset resins is therefore of considerable importance. Such resins could be used in future for composite applications, for coating applications or in adhesives.This thesis describes the development of biobased thermoset resins for composite applications. Thermoset resins were synthesised from both epoxidised soybean oils as well as from lactic acid. These resins have been characterised neat as well as together with various reinforcements. The main objective has been to study these biobased resins together with natural fibres for reinforcement, though to some extent nano-reinforcements and glass fibres have also been used as reinforcements.Natural fibre-reinforced composites were prepared from several different biobased thermoset resins. Resins based on soybean oil as well as a resin based on lactic acid were evaluated. The soybean resins were prepared by introducing acrylate or methacrylate groups into the molecules of soybean oil. The second type of thermoset resin used was based on lactic acid. This resin consists of star-shaped methacrylated oligomers of lactic acid. Natural fibres were impregnated by several impregnation techniques. Composites were prepared from the biobased resins together with various natural fibres, such as flax and hemp fibres. The resulting composites were evaluated by tensile testing, flexural testing, impact testing, DMTA and SEM. The results show that composites prepared from biobased resin have relatively good mechanical properties and can be used for indoor applications such as furniture and construction elements.
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| 47. |
- Åkesson, Dan, 1970, et al.
(författare)
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Synthesis and Characterization of a cross-linkable polylactic acid based resin
- 2010
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 115:1, s. 480-486
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Tidskriftsartikel (refereegranskat)abstract
- A new biobased polyester resin was developed for thermoset composite applications. The resin is potentially inexpensive and can be produced industrially by relatively simple means. The resin consists of star-shaped methacrylated oligomers of lactic acid (LA). LA oligomers were synthesized in a two-step process: in the first step, oligomers of LA were polymerized by direct condensation of LA. In the second step, the oligomers were end-functionalized by methacrylic anhydride. The resin was characterized by differential scanning calorimetry, Raman spectroscopy, NMR, rubber process analyzer, and TOF-SIMS. Tests show that the resin can be crosslinked into a rigid network within a couple of minutes upon thermal initiation.
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| 48. |
- Åkesson, Dan, 1970-, et al.
(författare)
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Thermo-oxidative aging of high-density polyethylene reinforced with multiwalled carbon nanotubes
- 2021
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Ingår i: Journal of Applied Polymer Science. - : College of William and Mary. - 0021-8995 .- 1097-4628. ; 138:26
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the influence of aging on the properties of high-density polyethylene (HDPE) reinforced with multi-wall carbon nanotubes (MWCNTs). Nanocomposites were prepared with nanotubes at 0, 1, 3, and 5 wt%. The long-term durability of the prepared materials was evaluated by thermo-oxidative aging test. Test bodies were aged at 110°C for up to 10 weeks. The nanocomposites were characterized by differential scanning calometry, thermogravimetric analysis (TGA), 13C-NMR, elongation at break, and transmission electron microscopy. The aging mainly occurred on the surface of the samples and the neat HDPE showed a strong yellowing after the aging. A strong reduction in elongation at break was seen. For neat HDPE, the elongation at break was reduced from roughly 1400–25%. When HDPE was reinforced with the nanotubes, the reduction was less dramatic
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