| 1. |
- Palme, Anna, 1986, et al.
(författare)
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Development of an efficient route for combined recycling of PET and cotton from mixed fabrics
- 2017
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Ingår i: Textiles and Clothing Sustainability. - : Springer Science and Business Media LLC. - 2197-9936. ; 3:4
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Tidskriftsartikel (refereegranskat)abstract
- Most textile waste is either incinerated or landfilled today, yet, the material could instead be recycled through chemical recycling to new high-quality textiles. A first important step is separation since chemical recycling of textiles requires pure streams. The focus of this paper is on the separation of cotton and PET (poly(ethylene terephthalate), polyester) from mixed textiles, so called polycotton. Polycotton is one of the most common materials in service textiles used in sheets and towels at hospitals and hotels. A straightforward process using 5–15 wt% NaOH in water and temperature in the range between 70 and 90 °C for the hydrolysis of PET was evaluated on the lab-scale. In the process, the PET was degraded to terephthalic acid (TPA) and ethylene glycol (EG). Three product streams were generated from the process. First is the cotton; second, the TPA; and, third, the filtrate containing EG and the process chemicals. The end products and the extent of PET degradation were characterized using light microscopy, UV-spectroscopy, and ATR FT-IR spectroscopy, as well as solution and solid-state NMR spectroscopy. Furthermore, the cotton cellulose degradation was evaluated by analyzing the intrinsic viscosity of the cotton cellulose. The findings show that with the addition of a phase transfer catalyst (benzyltributylammonium chloride (BTBAC)), PET hydrolysis in 10% NaOH solution at 90 °C can be completed within 40 min. Analysis of the degraded PET with NMR spectroscopy showed that no contaminants remained in the recovered TPA, and that the filtrate mainly contained EG and BTBAC (when added). The yield of the cotton cellulose was high, up to 97%, depending on how long the samples were treated. The findings also showed that the separation can be performed without the phase transfer catalyst; however, this requires longer treatment times, which results in more cellulose degradation.
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| 2. |
- Peterson, Anna, 1988, et al.
(författare)
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Dynamic Nanocellulose Networks for Thermoset-like yet Recyclable Plastics with a High Melt Stiffness and Creep Resistance
- 2019
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 20:10, s. 3924-3932
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Tidskriftsartikel (refereegranskat)abstract
- Many polymers, including polyethylene, feature a relatively low melting point and hence must be cross-linked to make them viable for applications that demand a high stiffness and creep resistance at elevated temperatures. The resulting thermoset plastics cannot be recycled, and therefore alternative materials with a reconfigurable internal network structure are in high demand. Here, we establish that such a thermoset-like yet recyclable material can be realized through the addition of a nanocellulose reinforcing agent. A network consisting of cellulose nanocrystals, nano- or microfibrils imparts many of the characteristics that are usually achieved through chemical cross-linking. For instance, the addition of only 7.5 wt % of either nanocellulose material significantly enhances the melt stiffness of an otherwise molten ethylene-acrylate copolymer by at least 1 order of magnitude. At the same time, the nanocellulose network reduces the meltcreep elongation to less than 10%, whereas the neat molten matrix would rupture. At high shear rates, however, the molten composites do not display a significantly higher viscosity than the copolymer matrix, and therefore retain the processability of a thermoplastic material. Repeated re-extrusion at 140 °C does not compromise the thermomechanical properties, which indicates a high degree of recyclability. The versatility of dynamic nanocellulose networks is illustrated by 3D printing of a cellulose composite, where the high melt stiffness improves the printability of the resin.
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| 3. |
- Mauri, Massimiliano, 1987, et al.
(författare)
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Byproduct-free curing of a highly insulating polyethylene copolymer blend: An alternative to peroxide crosslinking
- 2018
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7534 .- 2050-7526. ; 6:42, s. 11292-11302
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Tidskriftsartikel (refereegranskat)abstract
- High-voltage direct-current (HVDC) cables are a critical component of tomorrow's power grids that seamlessly integrate renewable sources of energy. The most advanced power cable technology uses crosslinked polyethylene (XLPE) insulation, which is produced by peroxide crosslinking of low-density polyethylene (LDPE). Peroxide crosslinking gives rise to hazardous byproducts that compromise the initially excellent purity and cleanliness of LDPE, and hence increase the electrical conductivity of the insulation material. Therefore, a byproduct-free curing process, which maintains the processing advantages and high electrical resistivity of LDPE, is in high demand. Here, we demonstrate a viable alternative to peroxide crosslinking that fulfils these requirements. Click chemistry reactions between two polyethylene copolymers allow the design of a curing process that is additive-free and does not result in the release of any byproducts. The thermoplastic copolymer blend offers a broad processing window up to 140 °C, where compounding and shaping can be carried out without curing. At more elevated temperatures, epoxy and acrylic acid functional groups rapidly react without byproduct formation to form an infusible network. Strikingly, the crosslinked copolymer blend exhibits a very low direct-current (DC) electrical conductivity of 2 × 10-16 S cm-1 at a typical cable operating temperature of 70 °C, which is on par with values measured for both ultra-clean LDPE and commercial XLPE. Hence, the use of polyethylene copolymer blends opens up the possibility to replace peroxide crosslinking with click chemistry type reactions, which may considerably expand the versatility of the most common type of plastic used today.
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| 4. |
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| 5. |
- Peterson, Anna, 1988, et al.
(författare)
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Synergistic reinforcement of a reversible Diels-Alder type network with nanocellulose
- 2021
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Ingår i: Materials Advances. - : Royal Society of Chemistry (RSC). - 2633-5409. ; 2:15, s. 5171-5180
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Tidskriftsartikel (refereegranskat)abstract
- Covalent adaptable networks are attractive intermediates between thermosets and thermoplastics. To achieve an optimal combination of dimensional stability at the temperature of use and macroscopic flow at elevated temperatures, materials that combine two reversible networks are highly sought after. We demonstrate that such a material can be created through the addition of cellulose microfibrils to a polymer matrix that can undergo thermoreversible Diels-Alder reactions. The cellulose microfibrils and crosslinked polymer form two independent reversible networks that display clear synergistic effects on the thermomechanical properties of the nanocomposite. Above the glass transition temperature of the polymer matrix the two networks work in tandem to reduce tensile creep by a factor of 40 at 80 degrees C, while increasing the storage modulus by a factor of 60 at the same temperature. The adaptability of the Diels-Alder network is not compromised by the addition of cellulose microfibrils, as shown by kinetic studies and repeated reprocessing. Further, the cellulose network significantly improves the dimensional stability at elevated temperatures where the Diels-Alder network dissociates.
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| 6. |
- Venkatesh, Abhijit, 1989, et al.
(författare)
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Cellulose nanofibril-reinforced composites using aqueous dispersed ethylene-acrylic acid copolymer
- 2018
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 25:8, s. 4577-4589
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Tidskriftsartikel (refereegranskat)abstract
- In order to explore the reinforcing capabilities of cellulose nanofibrils, composites containing high contents of cellulose nanofibrils were prepared through a combination of water-assisted mixing and compression moulding, the components being a cellulose nanofibril suspension and an aqueous dispersion of the polyolefin copolymer poly(ethylene-co-acrylic acid). The composite samples had dry cellulose nanofibril contents from 10 to 70 vol%. Computed tomography revealed well dispersed cellulose fibril/fibres in the polymer matrix. The highest content of 70 vol% cellulose nanofibrils increased the strength and stiffness of the composites by factors of 3.5 and 21, respectively, while maintaining an elongation at break of about 5%. The strength and strain-at-break of cellulose nanofibril composites were superior to the pulp composites at cellulose contents greater than 20 vol%. The stiffness of the composites reinforced with cellulose nanofibrils was not higher than for that of composites reinforced with cellulose pulp fibres. Graphical Abstract: [Figure not available: see fulltext.].
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| 7. |
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