| 1. |
- Orzan, Eliott Jean Quentin, 1995, et al.
(författare)
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Thermo-mechanical variability of post-industrial and post-consumer recyclate PC-ABS
- 2021
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Ingår i: Polymer Testing. - : Elsevier BV. - 0142-9418. ; 99
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work is to investigate the performance variability of post-industrial (PIR) and post-consumer recycled (PCR) polycarbonate acrylonitrile-butadiene-styrene (PC-ABS). In addition, necessary testing methodology for understanding polymer variation in recycled polymers are established. The thermal expansion behaviour of all tested material were found to be similar and FT-IR testing revealed no conclusive evidence of oxidative degradation. Both PIR and PCR exhibited similar levels of variation in mechanical properties compared with prime samples, with the exception of elongation at break and quasi-static impact behaviour. In these two tests, prime polymers showed lower variation and superior performance to both recycled polymers. The presence of defects and changes in molecular weight were determined to be leading causes of the reduced deformability. Our work contributes by identifying key areas where recycled PC-ABS show good potential as replacements for neat PC-ABS. Furthermore, the work demonstrates methods for material testing against performance criteria to pave way for effective replacement of neat PC-ABS with its recycled counterparts.
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| 2. |
- Orzan, Eliott Jean Quentin, 1995
(författare)
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Upgrading Cellulose Networks: Conquering Limitations in Fiber Foams
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The battle to create structural materials with low environmental impact demands the investiture of two champions: porous structures and cellulose substrates. The dominant solutions when constructing strong lightweight materials are plastic and metallic foams, while currently, cellulose fiber foams suffer from challenges which hamper their development. Cellulose foams are structurally promising, but are sensitive to humidity and fire, and often have an inferior mechanical performance compared to their plastic and metallic counterparts. In addition, standard foaming techniques for cellulose fiber foams use synthetic sodium dodecyl sulfate (SDS), a surfactant which weakens critical fiber-to-fiber contacts. In this work, two approaches were employed as solutions to strengthen cellulose foams: cross-linking of cellulose fibers, and controlling pore structure formation. Phytic acid (PA), a bio-based polyphosphate, was cross-linked to cellulose fibers with the goal of improving fiber-fiber bonding and generating flame-retardancy in SDS-based cellulose foams. Controlling pore structure formation was separately achieved by dispersing tert-butanol (TBA), a water miscible amphiphile, into cellulose-water suspensions. Addition of TBA induced the formation of hierarchical structures which vastly increased the surface area and mechanical performance of dried foams. The functionalities produced by the two presented solutions expand the potential applications for cellulose foams, and serve to encourage the development of these materials as lightweight competitors in the transportation, construction and packaging sectors.
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| 3. |
- Schaubeder, Jana B., et al.
(författare)
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Role of intrinsic and extrinsic xylan in softwood kraft pulp fiber networks
- 2024
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Ingår i: Carbohydrate Polymers. - 0144-8617. ; 323
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Tidskriftsartikel (refereegranskat)abstract
- Xylan is primarily found in the secondary cell wall of plants providing strength and integrity. To take advantage of the reinforcing effect of xylan in papermaking, it is crucial to understand its role in pulp fibers, as it undergoes substantial changes during pulping. However, the contributions of xylan that is added afterwards (extrinsic) and xylan present after pulping (intrinsic) remain largely unexplored. Here, we partially degraded xylan from refined bleached softwood kraft pulp (BSKP) and adsorbed xylan onto BSKP. Enzymatic degradation of 1 % xylan resulted in an open hand sheet structure, while adsorption of 3 % xylan created a denser fiber network. The mechanical properties improved with adsorbed xylan, but decreased more significantly after enzymatic treatment. We propose that the enhancement in mechanical properties by adsorbed extrinsic xylan is due to increased fiber-fiber bonds and sheet density, while the deterioration in mechanical properties of the enzyme treated pulp is caused by the opposite effect. These findings suggest that xylan is decisive for fiber network strength. However, intrinsic xylan is more critical, and the same properties cannot be achieved by readsorbing xylan onto the fibers. Therefore, pulping parameters should be selected to preserve intrinsic xylan within the fibers to maintain paper strength.
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| 4. |
- Schaubeder, Jana B., et al.
(författare)
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Xylan-cellulose thin film platform for assessing xylanase activity
- 2022
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 294
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Tidskriftsartikel (refereegranskat)abstract
- Enzymatic degradation of plant polysaccharide networks is a complex process that involves disrupting an intimate assembly of cellulose and hemicelluloses in fibrous matrices. To mimic this assembly and to elucidate the efficiency of enzymatic degradation in a rapid way, models with physicochemical equivalence to natural systems are needed. Here, we employ xylan-coated cellulose thin films to monitor the hydrolyzing activity of an endo-1,4-β-xylanase. In situ surface plasmon resonance spectroscopy (SPRS) revealed a decrease in xylan areal mass ranging from 0.01 ± 0.02 to 0.52 ± 0.04 mg·m−2. The extent of digestion correlates to increasing xylanase concentration. In addition, ex situ determination of released monosaccharides revealed that incubation time was also a significant factor in degradation (P > 0.01). For both experiments, atomic force microscopy confirmed the removal of xylans from the cellulose thin films. We provide a new model platform that offers nanoscale sensitivity for investigating biopolymer interactions and their susceptibility to enzymatic hydrolysis.
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