| 1. |
- Boz Noyan, Ezgi Ceren, 1990, et al.
(författare)
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Mechanical and Thermal Properties of Mixed PE Fractions from Post-Consumer Plastic Packaging Waste
- 2022
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:49, s. 45181-45188
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Tidskriftsartikel (refereegranskat)abstract
- The functional properties of recycled post-consumer flexible polyethylene packaging waste have been studied using materials collected and sorted at a large-scale facility in Sweden. The studied fraction was used both as received and after simple laboratory washing in water with added sodium hydroxide at 40 °C. The materials were melt-compounded with a twin-screw extruder using two different temperature profiles and two screw configurations and injection-molded into slabs, whose thermal and mechanical properties were assessed. The results showed that the mechanical properties of injection-molded samples were not changed significantly either by the washing or by the temperature or screw configuration used in the compounding. Washing reduced the viscosity and molecular mass to a minor extent. As expected, the ash content of the compounded pellets was reduced by washing. The thermo-oxidative stability decreased with increasing compounding temperature and with washing.
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| 2. |
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| 3. |
- Forsgren, Lilian, 1990, et al.
(författare)
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Composites with surface-grafted cellulose nanocrystals (CNC)
- 2019
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 54:4, s. 3009-3022
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Tidskriftsartikel (refereegranskat)abstract
- Hydroxyazetidinium salts were used to surface-modify cellulose nanocrystals (CNC) by grafting the salts onto the sulphate ester groups on the CNC surfaces. The grafting was confirmed by ζ-potential measurements and by the thermal degradation behaviour of the modified CNC. The thermal stability (onset of degradation) of the CNC was improved by the surface modification (almost 100 °C). Composites containing surface-modified or unmodified CNC (0.1, 1.0 and 10 wt%) with an ethylene-based copolymer as matrix were produced by compression moulding. The thermal stability of the composites was not, however, markedly improved by the surface grafting onto the CNC. It is suggested that this is due to a degrafting mechanism, associated with the alkaline character of the system, taking place at high temperatures. Model experiments indicated, however, that this did not occur at the conditions under which the composites were produced. Furthermore, in the case of a reference based on pH-neutralised polymeric system and modified CNC, an upward shift in the onset of thermal degradation of the composite was observed. The addition of the CNC to the polymer matrix had a strong influence of the mechanical performance. For example, the tensile modulus increased approximately three times for some systems when adding 10 wt% CNC. The surface grafting of the hydroxyazetidinium salts appeared mainly to affect, in a positive sense, the yield behaviour and ductility of the composites. The results of the mechanical testing are discussed in terms of interactions between the grafted units and the matrix material and between the grafted groups.
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| 4. |
- Forsgren, Lilian, 1990, et al.
(författare)
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Water-assisted extrusion and injection moulding of composites with surface-grafted cellulose nanocrystals – An upscaling study
- 2021
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Ingår i: Composites Part B: Engineering. - : Elsevier BV. - 1359-8368. ; 208
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Tidskriftsartikel (refereegranskat)abstract
- The large-scale surface modification of cellulose nanocrystals (CNC) was carried out to produce CNC-containing composites, in a scale of 3 kg, using industrial-scale melt processing techniques such as twin-screw extrusion and injection moulding. Two different polymer matrices, ethylene-acrylic acid copolymer (EAA) and low-density polyethylene (LDPE), were reinforced with 10 wt% unmodified cellulose nanocrystals (CNC) or surface-treated CNC, where a 2-hydroxyproyl-N-diallyl group had been grafted onto the sulphate half-ester groups on the CNC surfaces. This was achieved by mixing an aqueous CNC dispersion and the polymer pellets directly in the twin-screw extruder followed by a second dry compounding step prior to shaping by injection moulding. The injection-moulded materials were characterized with respect to their mechanical properties and thermal stability. The addition of 10 wt % CNC resulted in all cases in an increase in the yield strength and stiffness by 50–100%, most significantly for the EAA based composites. There were indications of the presence of a stable interphase and a percolating network in the EAA-based materials, according to dynamic-mechanical measurements. A reduction in thermal stability was observed for the melt-processed samples containing diallyl-modified CNC and discoloration in the EAA based samples.
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| 5. |
- Hosseini, Seyedehsan, 1994, et al.
(författare)
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Molybdenum disulphide—A traditional external lubricant that shows interesting interphase properties in pulp-based composites
- 2021
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Ingår i: Polymer Composites. - : Wiley. - 1548-0569 .- 0272-8397. ; 42:9, s. 4884-4896
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Tidskriftsartikel (refereegranskat)abstract
- Compression molded composites were prepared through a water-assisted mixing of an aqueous suspension of poly(ethylene-co-acrylic acid), additive, and pulp fibers [thermomechanical pulp (TMP) or dissolving pulp (DP)]. The lubricating additives used were magnesium stearate (MgSt) and molybdenum disulphide (MoS2). The composite materials had dry pulp contents ranging from 30 to 70 wt% and 5 wt% additive relative to the weight of the pulp. The adsorption of the additives onto the fibers was confirmed by scanning electron microscopy and energy dispersive X-ray analysis. DMA showed that MgSt and MoS2 gave similar interphase properties for the TMP samples at all loading contents, but the combination of MgSt and MoS2 improved the overall properties of the DP-based composites. The tensile modulus, at 70 wt% fiber content (TMP or DP), increased compared to the matrix by a factor of 6.3 and 8.1, without lubricants, and by a factor of 8 and 10.7, with lubricants, respectively. The increase in melt viscosity observed for the lubricated samples was greater for the TMP-based samples containing MoS2. At a lubricant content of 5 wt%, in 30 wt% TMP, the MoS2 behaved as both a lubricant and compatibilizer.
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| 6. |
- 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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| 7. |
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| 8. |
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| 9. |
- 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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| 10. |
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| 11. |
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| 12. |
- Venkatesh, Abhijit, 1989
(författare)
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Melt-processing and properties of thermoplastic composites based on ethylene-acrylic acid copolymer reinforced with wood nanocellulose
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Composites reinforced with cellulose nanofibers (CNF), both modified and unmodified cellulose nanocrystals (CNC) and pulp fibers have been prepared through small-scale and large-scale methods. The composites were produced by water-assisted dispersion mixing, drying and compression moulding on the laboratory scale and by extrusion and injection moulding for the large-scale production. The compression-moulded composites were stiffer and stronger by a factor of more than 10 for the CNF or pulp-based samples (>50 wt%) and by a factor of 3 for the CNC-based composites (at 10 wt%). The addition of a lubricant to pulp-based fibers resulted in a behaviour similar to that of a compatibilizer at low concentrations and to that of both compatibilizer and lubricant at higher concentrations. However, when the processing was scaled up, the improvement in properties was much less for the CNF-based and CNC-based composites after being melt-processed via extrusion and injection moulding, despite the fact that they showed a percolated cellulose network. Although the scale-up was successful, aggregates were observed. These aggregates could be reduced to some extent by changing the process design and parameters. Water-assisted extrusion was also used to reduce the aggregation but there was little improvement in properties. It is suggested that the extent of melt flow in the processing method influences the final properties of the composites, despite the nanoscale reinforcement.
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| 13. |
- Venkatesh, Abhijit, 1989, et al.
(författare)
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Melt Processing of Ethylene-Acrylic Acid Copolymer Composites Reinforced with Nanocellulose
- 2020
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 60:5, s. 956-967
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the impact of process design factors such as number of passes, screw design and screw type, a poly(ethylene-co-acrylic acid) and a masterbatch containing 40 vol% nanocellulose were compounded using a twin-screw extruder with two different screw configurations. The 20 vol% composite pellets obtained, containing nanocellulose of different morphologies, cellulose nanofibrils and cellulose nanocrystals, were re-extruded several times to study the effect of re-extrusion. The compounded pellets were extruded into films using a single-screw extruder. These films contained aggregates of the nanocellulose material, which was reduced in size upon re-extrusion leading to an improvement in properties of the composites. With the best combination of process factors, the Young's modulus and stress at break of the composites increased by factors of 10 and 1.6, respectively. The presence of a strong network of the cellulosic entities was observed qualitatively using melt rheology upon re-extrusion. Re-extrusion had a negligible effect on the crystallinity of the composites. POLYM. ENG. SCI., 2020. (c) 2020 The Authors. Polymer Engineering & Science published by Wiley Periodicals, Inc. on behalf of Society of Plastics Engineers.
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| 14. |
- Venkatesh, Abhijit, 1989, et al.
(författare)
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Plastcizing starch by adding magnesium chloride or sodium chloride
- 2017
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Ingår i: Starch/Staerke. - : Wiley. - 1521-379X .- 0038-9056. ; 68:5-6, s. Article no UNSP 1600191-
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim It is known that starch can form complexes with salts from transition and non-transition groups, but the effect of these salts on the properties of gelatinized starch systems and their potential as alternative plasticizers has been scantily reported. In this work, the effect of adding magnesium chloride or sodium chloride to gelatinized oxidized potato starch system have been investigated. Solution cast films were characterized by their equilibrium moisture content, X-ray diffraction spectra, dynamic mechanical thermal analysis, and tensile mechanical properties. The addition of a salt reduced the crystallinity and glass transition temperature of starch. The equilibrium moisture content increased when the Mg salt was added, but the salt recrystallization reduced the equilibrium moisture content at higher contents of NaCl. The addition of magnesium chloride resulted in lowered tensile strength and increased the elongation at break, whereas sodium chloride reduced both the tensile strength and the elongation at break.
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| 15. |
- Venkatesh, Abhijit, 1989, et al.
(författare)
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Water-assisted melt processing of cellulose biocomposites with poly(ε-caprolactone) or poly(ethylene-acrylic acid) for the production of carton screw caps
- 2022
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 139:6
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Tidskriftsartikel (refereegranskat)abstract
- Composites in 25 kg batches were compounded of cellulose nanocrystals (CNC) and thermomechanical pulp (TMP) and shaped into caps at industrial facilities on a pilot-plant scale. Some of the material was also injection molded into plaques to compare the effect of laboratory-scale and pilot-scale compounding of poly(ethylene-co-acrylic acid) (EAA7) and poly(caprolactone) composites reinforced with 10 wt% CNC and TMP. The materials compounded under laboratory-scale conditions showed a different morphology, improved mechanical properties, and a higher viscosity, than the materials compounded on a pilot-scale. In some cases, the rheological properties of the melts indicated the presence of a relatively strong percolating cellulosic network, and the interphase region between the cellulose and the matrix appears to be important for the mechanical performance of the composites. After the compounding on a pilot scale, both the length and width of the pulp fibers was reduced. The TMP provided better reinforcement than the CNC possibly due to the higher aspect ratio.
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| 16. |
- Venkatesh, Abhijit, 1989
(författare)
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Water-assisted mixing and compression moulding of ethylene-acrylic acid copolymer reinforced with nano-cellulose
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The concerns regarding aspects of global warming, depleting oil resources, accumulation of plastics in landfills has served as motivation to move towards utilizing sustainable and renewable resources to fulfil our needs. In the present work, the reinforcing capabilities of cellulose nanofibrils (CNF) and modified/unmodified cellulose nanocrystals (CNC) based composites prepared through water-assisted mixing, drying and compression moulding was explored. At the water-assisted mixing, compositions consisting of an aqueous dispersion of a poly(ethylene-co- acrylic acid) copolymer, nanocellulose suspension and excess water of about 96 %, were used to prepare the composites. The final composites had a dry loading content of 10 to 70 vol.% CNF or 0.1 – 10 wt.% CNC. The CNF based composites showed an increase in strength and stiffness with increasing cellulose nanofibril content. At the highest loading content of 70 vol.% the composites exhibited an improved strength and stiffness by a factor of 3.5 and 21, respectively while still maintaining an elongation of 5 %. The composites with 20 vol.% cellulose content confirmed a well dispersed reinforcement in the matrix through computed tomography. The composites had a stiffening threshold around 30 vol.% CNF content which coincided with the CNF concentration at which the effective stiffness of the composite was maximum. Furthermore, the strength and strain at break of CNF composites were higher than pulp based composites but the same could not be said for the stiffness. The CNC based composites on the other hand showed a strong influence of the CNC on yield behaviour and ductility of the composites, especially at higher CNC contents (10 wt.%). Dynamic mechanical analysis revealed indications of strong interactions between the grafted components and the matrix or between the grafted components themselves which was confirmed by the mechanical test data. However, the improved thermal stability of the modified CNC (almost 100 °C improvement) was not observed when they were introduced into the composites owing to alkalinity of the matrix that resulted in degrafting.
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