| 1. |
- Bek, Marko, et al.
(författare)
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Long-Term Creep Compliance of Wood Polymer Composites: Using Untreated Wood Fibers as a Filler in Recycled and Neat Polypropylene Matrix
- 2022
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 14:13
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Tidskriftsartikel (refereegranskat)abstract
- Neat (NPP) and recycled (RPP) polypropylene matrix materials were used to prepare wood–polymer composites with untreated wood fibers up to 40 wt.%. Long-term creep properties obtained through the time-temperature superposition showed superior creep resistance of composites with NPP matrix. In part, this is attributed to their higher crystallinity and better interfacial adhesion caused by the formation of a transcrystalline layer. This difference resulted in up to 25% creep compliance reduction of composites with NPP matrix compared to composites with recycled (RPP) polypropylene matrix, which does not form a transcrystalline layer between the fibers and polymer matrix. Despite the overall inferior creep performance of composites with RPP matrix, from the 20 wt.% on, the creep compliance is comparable and even surpasses the creep performance of unfilled NPP matrix and can be a promising way to promote sustainability.
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| 2. |
- Jan, Petra, et al.
(författare)
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Tribological behaviour of green wood-based unrecycled and recycled polypropylene composites
- 2023
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 524-525
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Tidskriftsartikel (refereegranskat)abstract
- In this study we evaluated the tribological performance of polypropylene composites with wood-flour fillers obtained as a by-product from the wood-processing industry, which were based on unrecycled and recycled polypropylene polymer matrices. The mechanical properties of polypropylene-wood composites with wood-filler loadings of 0–40 wt % were determined with tensile tests and their friction and wear behaviours were studied with dry reciprocating ball-on-disc sliding tests against 100Cr6 steel balls at room temperature. The addition of the wood fillers resulted in a significant improvement in the tribological performance compared to the neat, unrecycled, and recycled polypropylene materials: the friction coefficient decreased by up to 30%, while the wear resistance was improved by up to two orders of magnitude. While neat unrecycled polymers have better properties than recycled, addition of 40 wt % wood-filler content in both, recycled and unrecycled composites, resulted in almost the same level of coefficient of friction (∼0.25) and wear coefficient (2 × 10−6 mm3/(Nm) to 3 × 10−6 mm3/(Nm)). Even with the addition of as low as 5 wt % of wood fibres the wear resistance was improved for 63% and 43% for unrecycled and recycled composites, respectively, which indicates that the use of wood fillers could be a sustainable and cost-effective way to improve the polymer tribological performance, and could compensate for the normally poorer properties of recycled materials, making the recycled polypropylene-wood composites a suitable sustainable choice for tribological applications.
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| 3. |
- Podmiljšak, Benjamin, et al.
(författare)
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Additive-manufactured anisotropic magnets for harsh environments
- 2023
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Ingår i: Journal of Magnetism and Magnetic Materials. - 0304-8853. ; 586
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Tidskriftsartikel (refereegranskat)abstract
- We describe the fabrication of SrFe12O19-based filaments, using polyphenylene sulphide (PPS) as the binder for the magnetic particles, and the subsequent printing of this filament with a 3D printer. PPS is an ideal polymer for applications in harsh environments, making it applicable for the automotive industry, where it is widely used with injection moulding. However, 3D printing this polymer introduces a major challenge. Because PPS is more difficult to extrude than polyamide, the filling factor in this study was set to 70 wt. %, which is lower than when used in injection moulding (close to 90 wt. %). The filament with a diameter of 2.75 mm was printed into a disk-shaped magnet with a diameter of 10 mm and a height of 4 mm using a HAGE 3D printer that uses a belt system for the filament extrusion. The magnets were printed onto a glass surface and onto a bulk Nd-Fe-B permanent magnet with an external magnetic field, parallel to the printer’s z-axis. Printing in the presence of a magnetic field was found to increase the magnet’s remanent magnetization by 61%, compared to an isotropic print. Without an external magnetic field we achieved a remanence of 23.9 emu/g for the 70 wt.% filling fraction, while when printing in a magnetic field, the value of the remanence improved to 39.7 emu/g because of the improved magnetic texture.
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| 4. |
- Vadivel, Hari Shankar, et al.
(författare)
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Do the particle size, molecular weight, and processing of UHMWPE affect its thermomechanical and tribological performance?
- 2021
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Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854. ; 12, s. 1728-1737
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Tidskriftsartikel (refereegranskat)abstract
- UHMWPE has exhibited excellent performance when used as contact surfaces in tribological contacts. Traditionally, only UHMWPE grades, with narrow particle size and molecular weight distribution, have been deemed suitable for such applications. Now, various UHMWPE grades are available that are different from each other based on their particle size and molecular weight distribution. The question of whether the particle size of UHMWPE affects its performance and properties presents a research gap. The present study attempts to address this question. Additionally, the effect of processing of the UHMWPE is studied. It is observed that although minor differences were observed in the properties of the various grades of UHMWPE, they are inadequate to conclusively determine that the particle size and processing effect the properties and performance of the material.
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| 5. |
- Vukšić, Milan, et al.
(författare)
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The role of paraffin wax on the properties and printability of ethylene vinyl acetate-based feedstocks for alumina fused filament fabrication
- 2023
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Ingår i: Open Ceramics. - 2666-5395. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- Fused filament fabrication (FFF) is a versatile and inexpensive additive manufacturing (AM) technique for fabrication of complex shaped ceramic structures. The composition of the binder phase in ceramic-filled feedstock is crucial in determining its rheological behaviour during processing as well as the ability to obtain a defect-free part following debinding and sintering. In this study, the effect of paraffin wax (PW) addition to alumina feedstock with ethylene vinyl acetate (EVA) binder, on feedstock preparation, printability, and debinding has been investigated. The PW incorporation resulted in successful fabrication of a flexible filament with a bending (fracture) strain of 4±1 %. The addition of PW however did not have a significant impact on the debinding of the developed alumina filaments. The printed parts could only be successfully debinded up to 2 mm wall thickness. The subsequent sintering of the debinded parts resulted in a relative density of 98 %.
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