| 1. |
- Cho, Sung-Woo, 1974-
(författare)
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Protein-based Packaging Films, Sheets and Composites: Process Development and Functional Properties
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The depletion of the petroleum resources and a number of environmental concerns led to considerable research efforts in the field of biodegradable materials over the last few decades. Of the diverse range of biopolymers, wheat gluten (WG) stands out as an alternative to synthetic plastics in packaging applications due to its attractive combination of flexibility and strength, high gas barrier properties under low humidity conditions and renewability. The availability of raw materials has also been largely increased with an increase in the production of WG as a low-cost surplus material due to increasing demand for ethanol as fuel. In this study, WG was processed into films, sheets and composites using some of the most widely used techniques including solution casting, compression molding, extrusion and injection molding, accompanying process optimizations and characterization of their functional properties. This thesis consists mainly of six parts based on the purpose of the study. The first part addresses the aging and optical properties of the cast film in order to understand the mechanisms and reasons for the time-dependant physical and chemical changes. The films plasticized with glycerol were cast from acidic (pH 4) and basic (pH11) solutions. The film prepared from the pH 11 solution was mechanically more stable upon aging than the pH 4 film, which was initially very ductile but became brittle with time. It was revealed that the protein structure of the pH 4 film was initially less polymerized/aggregated and the polymerization increased during storage but it did not reach the degree of aggregation of the pH 11 film. During aging, the pH 4 film lost more mass than the pH 11 film mainly due to migration of glycerol but also due to some loss of volatile mass. In addition the greater plasticizer loss of the pH 4 film was presumably due to its initial lower degree of protein aggregation/polymerization. Glycerol content did not significantly change the opacity and pH 4 films showed good contact clarity because of less Maillard reaction. In the second part, the heat-sealability of WG films was investigated, using an impulse-heat sealer, as the sealability is one of the most important properties in the use of flexible packaging materials. It was observed that the WG films were readily sealable while preserving their mechanical integrity. The sealing temperature had a negligible effect on the lap-shear strength, but the peel strength increased with sealing temperature. The lap-shear strength increased with increasing mold temperature and the failure mode changed. The third part describes the possibility of using industrial hemp fibers to reinforce wheat gluten sheets based on evaluation of the fiber contents, fiber distribution and bonding between the fibers and matrix. It was found that the hemp fibers enhanced the mechanical properties, in which the fiber contents played a significant role in the strength. The fiber bonding was improved by addition of diamine as a cross-linker, while the fiber distribution needed to be improved. The fourth part presents a novel approach to improve the barrier and mechanical properties of extruded WG sheets with a single screw extruder at alkaline conditions using 3-5wt.% NaOH with or without 1 wt.% salicylic acid. The oxygen barrier, at dry conditions, was improved significantly with the addition of NaOH, while the addition of salicylic acid yielded poorer barrier properties. It was also observed that the WG sheets with 3 wt.% NaOH had the most suitable combination of low oxygen permeability and relatively small time-dependant changes in mechanical properties, probably due to low plasticizer migration and an optimal protein aggregation/polymerization. In the fifth part WG/PLA laminates were characterized for the purpose of improving the water barrier properties. The lamination was performed at 110°C and scanning electron microscopy showed that the laminated films were uniform in thickness. The laminates significantly suppressed the mass loss and showed promising water vapor barrier properties in humid conditions indicating possible applications in packaging. The final part addresses the development of injection molding processes for WG. Injection-molded nanocomposites of WG/MMT were also characterized. WG sheets were successively processed using injection molding and the process temperatures were found to preferably be in a range of 170-200°C, which was varied depending on the sample compositions. The clay was found to enhance the processability, being well dispersed in the matrix. The natural clay increased the tensile stiffness, whereas the modified clay increased the surface hydrophobicity. Both clays decreased the Tg and increased the thermal stability of the nanocomposites. The overall conclusion was that injection molding is a promising method for producing WG items of simple shapes. Further studies will reveal if gluten can also be used for making more complex shapes.
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| 2. |
- Das, Oisik, et al.
(författare)
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Functionalised biochar in biocomposites: The effect of fire retardants, bioplastics and processing methods
- 2023
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Ingår i: Composites Part C: Open Access. - : Elsevier. - 2666-6820. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Fire retardants, although can impart fire-safety in polymeric composites, are detrimental to the mechanical properties. Biochar can be used, in conjunction with fire retardants, to create a balance between fire-safety and mechanical performance. It is possible to thermally dope fire retardants into the pores of biochar to make it functionalised. Thus, the current work is intended in identifying a composite having the combination of the most desirable fire retardant, bioplastic, and a suitable processing method. A comparison was made between two fire retardants (lanosol and ammonium polyphosphate), bioplastics (wheat gluten and polyamide 11), and composite processing methods (compression and injection moulding). It was found that wheat gluten containing ammonium polyphosphate-doped biochar made by compression moulding had the best fire-safety properties with the lowest peak heat release rate (186 kW/m2), the highest fire performance index (0.6 m2s/kW), and the lowest fire growth index (1.6 kW/ms) with acceptable mechanical properties compared to the corresponding neat bioplastic. Thus, for gluten-based polymers, the use of ammonium polyphosphate thermally doped into biochar processed by compression moulding is recommended to both simultaneously improve fire-safety and conserve the mechanical strength of the resulting biocomposites.
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| 3. |
- Mensah, Rhoda Afriyie, et al.
(författare)
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Influence of biochar and flame retardant on mechanical, thermal, and flammability properties of wheat gluten composites
- 2022
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Ingår i: Composites Part C: Open Access. - : Elsevier. - 2666-6820. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The use of environmentally friendly materials such as bio-sourced plastics is being driven by increased awareness of environmental issues caused by synthetic plastics. However, bio-sourced plastics have poor fire behaviour that limits their application. The addition of a flame retardant to these plastics is one effective way to increase the fire resistance property; however, the flame retardant should not interfere with the mechanical performance of the plastic. Most flame retardants act as stress concentration points, reducing tensile strength. Hence, to create a balance between tensile strength and fire resistance, biochar (to conserve strength) and lanosol (to improve fire resistance) were added to wheat gluten bioplastic in various ratios and the optimal ratio was identified. Wheat gluten composites were fabricated using compression moulding at four different concentrations of lanosol (2, 4, 6, and 8 wt.%) and biochar (2, 4, 6, and 8 wt.%). From the test results, the composite with 4 wt.% lanosol and 6 wt.% biochar exhibited a good balance between the mechanical and fire properties; it conserved the strength and improved the fire properties (39 % reduction in peak heat release rate).
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| 4. |
- Mohanty, Amar K., et al.
(författare)
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Biocarbon materials
- 2024
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Ingår i: Nature Reviews Methods Primers. - : Springer Nature. - 2662-8449. ; 4:1
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Tidskriftsartikel (refereegranskat)
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| 5. |
- Varsally, Zohrah B., et al.
(författare)
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A sustainable approach for developing biocarbon from lignin and its utilization in recycled ocean nylon based biocomposites
- 2023
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Ingår i: Composites Part C: Open Access. - : Elsevier B.V.. - 2666-6820. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Nylon/polyamide (PA6) is a major cause of ocean plastic pollution because of its extended use in commercial fishing activities. Recovery of this nylon from oceans and its use in manufacturing new materials or composites is urgently required to promote sustainability and circularity. In this work, unlike higher-density mineral fillers, lignin from the forestry industry was converted into biocarbon, which was used as a lightweight filler to manufacture recycled-ocean nylon (RN)-based composites. Biocarbon is a highly stable, competitive, and sustainable filler for high-performance engineering plastics such as nylon. Lignin was pyrolyzed at 600 °C followed by further treatment at 1200 °C (with and without cobalt (II) nitrate catalyst) to induce graphitization in the produced biocarbon. Among the three types of biocarbon samples, such as pyrolyzed at 600 °C, 1200 °C and 1200 °C catalyzed lignin biocarbon, the catalyzed biocarbon showed the maximum electrical conductivity. Catalyzed lignin biocarbon pyrolyzed at 1200 °C showed an increase of 85% in electrical conductivity compared to commercial mineral graphite. The biocomposites consisting of 600 °C biocarbon were manufactured by injection molding at different filler contents up to 40 wt.%. The biocomposites consisting of 40% of pyrolyzed lignin at 600 °C showed increased flexural strength, flexural modulus, and heat deflection temperature by 41, 76 and 76%, respectively, compared to neat RN. Improved properties of the prepared biocarbons and biocomposites showed the potential of RN-based composites in the automotive industries.
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| 6. |
- Vijaybabu, T. R., et al.
(författare)
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High Thermal Conductivity Polymer Composites Fabrication through Conventional and 3D Printing Processes: State-of-the-Art and Future Trends
- 2023
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Ingår i: Macromolecular materials and engineering. - : John Wiley & Sons. - 1438-7492 .- 1439-2054. ; 308:7
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Forskningsöversikt (refereegranskat)abstract
- The lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials.
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