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    Development of resorbable “Springs” for surgery
    (2024) Bauer, Sara; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Ström, Anna; Stubelius, Alexandra
    The demand for replicating the functionality of conventional stainless steel springs with degradable and biocompatible materials has led to the exploration of alternative methods. Current trends focus on understanding the genetic and cellular causes of craniosynostosis rather than its treatment. Nonetheless, research has investigated gelatin scaffolds supporting suture regeneration with mesenchymal stem cells, protein-releasing Titania nanotubular implants that inhibit bone formation, and a bioabsorbable material blend of poly(lactic-co-glycolic acid) (PLGA) and polyisoprene (PI). Furthermore, advancements in 3D printing technology now enable the production of implantable objects, sparking interest in printing cranial spring implants, particularly for addressing sagittal craniosynostosis. Polylactic acid (PLA) was 3D printed, mechanical strength tested using force strain measurements and degradation was followed using PBS. PLGA/PI blends were prepared according to the suggested method, miscibilty and degradation in PBS at pH 7.4 and 5 were tested. Printed PLA samples with different filling patterns demonstrated high load-bearing capacity, averaging 2109 N, which scales to 527 N for implant size, surpassing the 8 N threshold of stainless steel springs. After one month, PLA showed no significant degradation, suggesting that this material lasts longer than the expected 4-6 months. A literature review was also conducted to assess existing methods and future directions in the field. This review provided valuable context for understanding current practices and emerging trends. Research into alternative materials led to the discovery of a promising PLGA/PI blend that had already been tested in rabbits [9]. The molding process and the immiscibility of the material became a major limitation for its use as a potential implant, even tough its degradation process seems promising.
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    Optimization of bio-oil purification: enabling a wider feedstock for replacing fossil alternatives
    (2024) Nilsson, Johan; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Olsson, Louise; Olsson Månsson, Emma
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    Sustainable catalysts for filled and unfilled silane cross-linked polymer systems
    (2024) Wang, Ren; Porota, Alex; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Ström, Anna; Gschneidtner, Tina; Prieto, Oscar; Hesselgren, Jessica; Antonsson,, Jennie
    Since the polymer used to make up cables is combustible and has the potential to ignite a fire, fire safety concerns about cables receive a lot of attention. This concern prompts an urgent need to address safety issues and drives the global development of flame retardant polymeric systems. Dioctyltin dilaurate (DOTL) is an organotin catalyst that is frequently used in silane cross-linking for flame retardant polymeric systems. However, DOTL is toxic and has a reprotoxic impact on humans. This study focuses on investigating robust and sustainable catalysts which can be utilized for various silane cross-linked polymeric systems to replace DOTL. Both filled and unfilled silane cross-linked polymer systems were investigated with various types of catalysts, including four polymer systems (Polymer A, B, C, and D) and four catalysts (Catalyst 1, 2, 3, and DOTL as reference). Tapes made with various amounts of polymer base resin and catalyst masterbatch were crosslinked in ambient conditions and hot water baths. Two analytical techniques, XRF and FTIR, were used for analyzing catalyst masterbatches. Visual observation was utilized to evaluate tape surface quality. The crosslinking of different tapes was measured by hot set testing method. The results showed that when catalyst 3 is extruded with the unfilled polymer A, highly filled polymer B and C, tapes showcased very good surface qualities and good cross-linking in ambient conditions. The catalyst also displayed good cross-linking in hot water bath for polymer A and C. Catalyst 1 and 2 cross-linked unfilled and some filled polymer systems in hot water bath and ambient conditions but the tapes had bad surface qualities.
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    A literature study of the etching process on nickel- and titanium-based superalloys - The chemical reactions at the metal-liquid interface
    (2024) Appelqvist, Henrik; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Skoglundh, Magnus; Skog Brönnestam, Monica
    In the aerospace industry, the requirement for material properties and product safety are among the most important factors to consider in order to ensure the safety and reliability of the aircrafts. During the manufacturing process, the formation of cracks in the material might occur. For example, polishing of a region in the close vicinity of a crack can smear the metallic material over the cracks. This would result in that the crack could go undetected through quality control. Additionally, the oxides formed during heat treatment were shown to have high chemical stability and would cause trouble during removal. Therefore, in this literature study, the oxidation behavior of nine highly relevant aerospace materials were examined together with the effect of six common etching solutions. Furthermore, the relationship between etch rate with temperature and concentration of each etching solution was also explored. The study found that the pure metals, in most cases, were dissolved by the etching solutions with a few exceptions where passive reaction products were formed on the surface. Passive reaction products restricted diffusion of metallic elements out towards the oxidizing environment and vice versa. These would instead have the opposite effect on the etch rate where it would decrease as the reaction progressed due to the growing thickness of the metal oxides. A similar behavior could be seen by the metal oxides, but the oxidizing etching solutions and the acetic acid, weak acid, could not affect the metal oxides. An increased temperature and concentration of etching solution, did in most cases lead to an increased rate. Exceptions from the trend showed that some acids had an optimal concentration at which the reaction could ensue. The primary variable was the acids ability to dissociate which occurs when water is present. Therefore, the etch rate would decrease at very high concentrations due to the lack of water. Although this literature study can give an insight in the etching process, or more specifically the reactions that occur at the interface between the metallic material and the etching solution, further work is needed to achieve a deeper understanding of the application on a larger scale.
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    Laser pre-treatment of aluminum - An investigation of the adhesive bonding after surface modification
    (2024) Sellén, Hannes; Björkman, Wilma; Chalmers tekniska högskola / Institutionen för kemi och kemiteknik; Chalmers University of Technology / Department of Chemistry and Chemical Engineering; Skoglundh, Magnus; Wasmuth, Kerstin
    This project focused on the laser pre-treatment of aluminum sheet and extruded aluminum within the 6xxx-series, applied on battery pack applications at Volvo Cars. Laser parameters were evaluated by surface characterization and lap shear testing, correlating adhesion to surface properties. Four different adhesives were investigated together with three different laser parameters. The results were compared towards untreated surfaces as well as plasma treated surfaces. Results showed that laser effectively cleaned the treated surfaces, and that it altered the surface structure. Clean and structured surfaces was shown to improve adhesion by increasing the strength, and giving a more favorable failure mode of the adhesives. After tropical ageing, three of the adhesives increased in strength due to post curing, whereas one degraded below the desired strength. XPS measurements showed that laser treatment induced thermal oxide growth, and confirmed cleanliness results, both enabling stronger bonding. The oxide layer thickness of untreated aluminum was 3–4 nm, while laser treated surfaces showed oxide thickness of 25–55 nm. SEM-EDX was not applicable to study the oxide layers due to insufficient resolution. Laser parameter T2 showed the greatest potential, however new sets of laser parameters need to be studied, with a particular emphasis on a high %overlap scan.