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2. Degradation and Stabilization of Polymer MaterialsBranka Mušič, Andrijana Sever Škapin, 2023, short scientific article Keywords: polymer-based materials, nano, micro, and macro composites, effects on (micro) organisms and toxicity, impact on the ecosystem, mechanisms and products of accelerated aging and degradation, physical, chemical, mechanical, thermal, and morphological, analysis, biodegradability, sustainability, life cycle, renewable and recycled resources and the circular economy
Published in DiRROS: 21.12.2023; Views: 257; Downloads: 91
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3. Remediation of contaminated soil by red mud and paper ashPrimož Oprčkal, Ana Mladenovič, Nina Zupančič, Janez Ščančar, Radmila Milačič, Vesna Zalar Serjun, 2020, original scientific article Abstract: Remediation of contaminated soil can be performed by using various techniques, which must be adequately tailored for each specific case. The aim of this research is to critically evaluate the potential use of red mud and paper ash and a combination of the two as immobilization additives for the remediation of contaminated soil from one of the most polluted sites in Slovenia. The proposed procedure involves the preparation of geotechnical composites made from contaminated soil and mixed with 25 wt% of immobilization additives and an optimal quantity of water to achieve consistency, at which maximum compaction according to the Proctor Compaction Test procedure can be achieved. The results reveal a positive, time-dependent trend for the immobilization of potentially toxic elements in the composite with paper ash, because of the formation of the new hydration products with potentially toxic elements. In a composite containing only red mud, potentially toxic elements were immobilized by sorption mechanisms with no general time-dependent trends. The composite with a combination of additives demonstrates the remediation characteristics of both red mud and paper ash. Using this approach excavated contaminated soil, red mud and paper ash can be successfully recycled in the proposed composites, which can be beneficially used in situ for rehabilitation of contaminated sites. Nevertheless, mobilization of some potentially toxic elements at high pHs may represent a limiting factor and has to be taken into the consideration when a combination of red mud and paper ash is used as immobilization additive.
Keywords: red mud, paper ash, contaminated soil, potentially toxic elements, geotechnical composites
Published in DiRROS: 31.08.2023; Views: 290; Downloads: 231
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4. Antifungal effect of polymethyl methacrylate resin base with embedded Au nanoparticlesIvan Marić, Anamarija Zore, Franc Rojko, Andrijana Sever Škapin, Roman Štukelj, Aleksander Učakar, Rajko Vidrih, Valentina Veselinović, Marijan Gotić, Klemen Bohinc, 2023, original scientific article Abstract: Full and partial restorations in dentistry must replicate the characteristics of the patient’s natural teeth. Materials must have good mechanical properties and be non-toxic and biocompatible. Microbes, which can form biofilms, are constantly in contact with restorations. In this study, we investigate how well Candida albicans adheres to a polymethyl methacrylate (PMMA) resin base with gold (Au) nanoparticles. We synthesized Au nanoparticles and characterized them. The average size of Au nanoparticles embedded in PMMA was 11 nm. The color difference ∆E between PMMA and PMMA/Au composites was 2.7 and was still esthetically acceptable to patients. PMMA/Au surfaces are rougher and more hydrophilic than pure PMMA surfaces, and the isoelectric point of both types of surfaces was 4.3. Above the isoelectric point, PMMA/Au surfaces are more negatively charged than PMMA surfaces. The added Au nanoparticles decreased the tensile strength, while the hardness did not change significantly. Adhesion measurements showed that PMMA surfaces modified with Au nanoparticles reduced the extent of microbial adhesion of Candida albicans.
Keywords: fungal adhesión, C. albicans, polymethyl methacrylate resin, Au, surface properties, composites
Published in DiRROS: 24.07.2023; Views: 353; Downloads: 140
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5. Impact of metakaolin on mechanical performance of flax textile-reinforced cement-based compositesFilip Majstorović, Václav Sebera, Maruša Mrak, Sabina Dolenec, Marco Wolf, Laetitia Sarah Jennifer Marrot, 2022, original scientific article Abstract: This study presents research on the effect of Portland cement (PC) replacement with metakaolin on the mechanical behavior of flax textile-reinforced cementitious matrices (TRCM). The composition of cementitious matrices and in-situ flax fibres was determined using X-ray diffraction and thermogravimetric analysis, while the reinforcement efficiency of the textile and mechanical behavior of TRCMs was investigated by three-point bending tests and finite element analysis. High amounts of PC replacement with metakaolin provided a calcium hydroxide-free environment, more suitable for the natural fibres, to avoid their degradation and embrittlement and, thus, significantly contribute to the ductility of the cement-based composite material.
Keywords: textile-reinforced concrete (TRC), flax textile, natural fibres, finite element, metakaolin, cement-based composites, open access
Published in DiRROS: 22.05.2023; Views: 369; Downloads: 175
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6. Improved synthetic route of incorporation of nanosilicon species into phenol-formaldehyde resin and preparation of novel ZnAl-layered double-hydroxide hybrid phenol-formaldehyde resinAna Dremelj, Romana Cerc Korošec, Andreja Pondelak, Branka Mušič, 2022, original scientific article Abstract: Hybrid phenol-formaldehyde (PF) resins represent one of the most important niche groups of binding systems for composites. New industrial needs, environmental requirements, and price fluctuations have led to further research on materials with enhanced mechanical and thermal properties. The preparation of novel hybrid materials can be achieved by inclusion of various elements or functional groups in the organic polymer phenolic framework. Herein, we report the synthesis and characterization of a PF-based hybrid material with different nanoscale silicone species and ZnAl-layered double hydroxide (LDH). The main goals of this study were to improve the synthetic pathways of hybrid resin, as well as to prepare granulated composite materials and test samples and determine their characterization. Added inorganic species increased the glass-transition temperature by a minimum of 8 °C, which was determined using differential scanning calorimetry (DSC). Rheological properties (melting viscosity and flow distance) of the hybrid resin were measured. The homogeneity of distribution of added species across the organic matrix was evaluated with scanning electron microscopy (SEM). With synthesized new hybrid-binding systems, we prepared different granulated composite materials and evaluated them with the measurements of rheological properties (flow curing characteristics). Tensile strength of samples, prepared from granulated composite material, improved by more than 5%.
Keywords: phenol-formaldehyde hybrid resins, nano-SiO2, ZnAl-LDH, composites, glass-transition temperature, mechanical properties
Published in DiRROS: 03.05.2023; Views: 379; Downloads: 164
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