| 1. |
- Hosseini, Seyedehsan, 1994, et al.
(författare)
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Alkyl ketene dimer modification of thermomechanical pulp promotes processability with polypropylene
- 2024
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Ingår i: Polymer Composites. - 1548-0569 .- 0272-8397. ; 45:1, s. 825-835
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Tidskriftsartikel (refereegranskat)abstract
- Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP-TMP-AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP.
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| 2. |
- Hosseini, Seyedehsan, 1994, et al.
(författare)
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Reducing friction between metal and thermo-mechanical pulp using alkyl ketene dimers and magnesium stearate
- 2024
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Ingår i: Tribology International. - 0301-679X. ; 192
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Tidskriftsartikel (refereegranskat)abstract
- The friction between natural fibers and metal affects tool life, wear and tear and surface defects of extrudates. The ability of alkyl ketene dimer (AKD) and magnesium stearate (MgSt) to reduce coefficient of friction (COF) between thermomechanical pulp (TMP) and metal were determined at temperatures of 30, 100, and 180 °C and additive concentrations from 0.5 to 5 wt%. The AKD and MgSt were added to TMP sheets through spraying, followed by drying. ATR-FTIR and IR microscopy confirmed the presence of AKD and MgSt on the TMP. AKD addition at 2 wt%, consistently reduced the COF of TMP and metal, whereas MgSt reduced COF at 100 and 180 °C, only. No further reduction in COF was observed at 5 wt% of AKD or MgSt.
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| 3. |
- Hosseini, Seyedehsan, 1994
(författare)
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A toolbox for improving the processability of composites with a high content of thermomechanical pulp
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of oil-based products causes large volumes of non-biodegradable waste and contributes to climate changes. Focus has consequently shifted towards the use of polymers derived from wood. The processability of such polymers, however, presents a challenge but this can be overcome through the use of composite materials, i.e., a blend of wood-derived material and fossil fuel-based polymers. Wood-derived material requires either additives or modification in order to achieve high loading of the renewable polymer section. Two possible routes for modifying thermomechanical pulp (TMP) are outlined here, with the aim of achieving composites with a high content of TMP that not only have good mechanical properties but are also processable. The addition of physical modifiers, such as magnesium stearate (MgSt) and molybdenum disulfide (MoS2), and their effects on the matrix of polyolefin copolymer poly (ethylene-co-acrylic acid (EAA)) in the TMP loading were the first route studied. The composites were prepared by compression moulding and had dry TMP contents of 30, 50 and 70 wt%, respectively, and 5 wt% additive relative to the weight of TMP. The second route was chemical modification of TMP fibres using three different alkyl ketene dimers (AKD), and was tested within the matrix of polypropylene (PP). The AKDs had carbon chains that were 6, 12 and 18 carbons in length. The AKD-modified TMP was extruded with PP at 50 wt% TMP. The addition of TMP increased the mechanical strength of the composites, independent of matrix (EAA or PP). The addition of MgSt or MoS2 increased the strength of the TMP-EAA composites further. Also, the presence of MoS2 improved the interface compatibility between EAA and TMP, as revealed by the use of rheology. In the case of AKD-modified TMP, surface energy measurements showed that modification reduced the surface energy of the fibres and increased hydrophobicity. The colour, shape of the extruded filament and reduced complex viscosity all indicate the easier processability of the TMP modified with the longest AKD carbon chain. It may be concluded that both the physical and chemical modifications made showed improvements in the processability of these composites.
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| 4. |
- Hosseini, Seyedehsan, 1994
(författare)
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Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Efforts to address environmental concerns have resulted in new regulations designed to plan the reduction of plastic and synthetic polymer usage, necessitating the search for sustainable natural alternatives with comparable cost-effectiveness and mechanical performance. Thermomechanical pulp (TMP) fibres are one of the most affordable natural fibres that have no chemical refining in production, production have a high yield of 90-98% and TMP fibres have been demonstrated to improve the mechanical characteristics (strength, stiffness and toughness) of wood-polymer composites (WPCs) compared to the pure polymer. The integration of TMP fibres with non-polar synthetic polymers remains a challenge due to surface polarity differences. This PhD thesis aims to ease the processing of TMP fibre composites through the incorporation of additives. The hypothesis posits that incorporating magnesium stearate (MgSt), molybdenum disulfide (MoS2) and alkyl ketene dimer (AKD) as additives in TMP composites will enhance interfacial properties, resulting in improved processability and flow behaviour at high temperatures. MoS2 is known for its interaction with lignin, which exists in TMP and MgSt is recognised for its ability to improve flow in pharmaceutical processing when combined with cellulose, also a component of TMP. AKD modifies the hydrophilic properties of lignocellulosic surfaces. The experimental work explores the effect of these additives on the properties of TMP composites of ethylene acrylic acid copolymer (EAA) and polypropylene (PP) matrices. The dynamic mechanical analysis (DMA) and mechanical analysis results reveal that MoS2 exhibits superior interaction with TMP fibres, yielding enhanced interfacial properties compared to MgSt in between EAA and TMP fibres. Rheological studies elucidate the transition from a fluid-like state to a network-like structure upon the incorporation of TMP into the PP matrix. The incorporation of AKD with C18 reduces the viscosity of TMP-PP composites and PP itself, and, as determined through theoretical Hansen solubility parameter (HSP) calculations, increases compatibility between cellulose in TMP fibres and PP. The addition of AKD influences both the colour (lighter) and shape (smoother surface) of the extrudate filaments in the TMP-PP composites, indicative of improved processing. In addition, frictional analysis demonstrates the reduction of the coefficient of friction (COF) between metal and TMP fibre by MgSt and AKD treatments.
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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. |
- Sonker, Amit Kumar, 1989, et al.
(författare)
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Exfoliated MoS 2 Nanosheet/Cellulose Nanocrystal Flexible Composite Films as Electrodes for Zinc Batteries
- 2023
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Ingår i: ACS Applied Nano Materials. - 2574-0970. ; 6:10, s. 8270-8278
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Tidskriftsartikel (refereegranskat)abstract
- The study presents a more efficient way of exfoliating MoS2 in water and the exfoliated MoS2 was used in an electrode. The electrodes were prepared from exfoliated MoS2 (active material)-nanocrystalline cellulose (binder) with carbon nanotubes (electron-conducting support) and demonstrated in a zinc battery half-cell that showed a Coulombic efficiency of 90%. Successful exfoliation of MoS2 was done by sonication of bulk MoS2 with sulfated cellulose nanocrystals (CNC) for 4 h. The exfoliation was confirmed by Raman and transmission electron microscopy; interestingly, the Raman signals for exfoliated MoS2 show a blue shift for both A1g and E2g1 bands, which may be an indication of an induced lattice strain effect from the CNC on MoS2. The resulting stable water suspension showed no tendency of precipitation after 2 months of standing. The zeta potential, ζ, for sodium sulfated CNC (CNC-OSO3Na)-MoS2 in water suspension was −45 mV, whereas sulfated CNC (CNC-OSO3H)-MoS2 in water suspension had a zeta potential of −35 mV. The sodium form of sulfated CNCs displayed micelle characteristics, similar to sodium dodecyl sulfate (SDS), with a critical aggregation concentration (CAC) of 1.1 wt %. At CAC, the CNCs efficiently exfoliated MoS2, which is at a much lower concentration than has been reported for synthetic surfactants like SDS and cetyl trimethyl ammonium bromide.
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