1. Effect of micro- and nano-lignin on the thermal, mechanical, and antioxidant properties of biobased PLA–lignin composite filmsSofia P. Makri, Eleftheria Xanthopoulou, Panagiotis A. Klonos, Alexios Grigoropoulos, Apostolos Kyritsis, Konstantinos Tsachouridis, Antonios Anastasiou, Ioanna Deligkiozi, Nikolaos P. Nikolaidis, Dimitrios Bikiaris, 2022, original scientific article Abstract: Bio-based poly(lactic acid) (PLA) composite films were produced using unmodified soda
micro- or nano-lignin as a green filler at four different contents, between 0.5 wt% and 5 wt%. The PLA–
lignin composite polymers were synthesized by solvent casting to prepare a masterbatch, followed by
melt mixing. The composites were then converted into films, to evaluate the effect of lignin content
and size on their physicochemical and mechanical properties. Differential scanning calorimetry
(DSC), supported by polarized light microscopy (PLM), infrared spectroscopy (FTIR-ATR), X-ray
diffraction (XRD), and transmission electron microscopy (TEM) were employed to investigate the
PLA crystallization and the interactions with Lignin (L) and Nanolignin (NL). The presence of
both fillers (L and NL) had a negligible effect on the glass transition temperature (chain diffusion).
However, it resulted in suppression of the corresponding change in heat capacity. This was indicative
of a partial immobilization of the PLA chains on the lignin entities, due to interfacial interactions,
which was slightly stronger in the case of NL. Lignin was also found to facilitate crystallization, in
terms of nucleation; whereas, this was not clear in the crystalline fraction. The addition of L and
NL led to systematically larger crystallites compared with neat PLA, which, combined with the
higher melting temperature, provided indications of a denser crystal structure in the composites. The
mechanical, optical, antioxidant, and surface properties of the composite films were also investigated.
The tensile strength and Young’s modulus were improved by the addition of L and especially NL.
The UV-blocking and antioxidant properties of the composite films were also enhanced, especially
at higher filler contents. Importantly, the PLA–NL composite films constantly outperformed their
PLA–L counterparts, due to the finer dispersion of NL in the PLA matrix, as verified by the TEM
micrographs. These results suggest that bio-based and biodegradable PLA films filled with L, and
particularly NL, can be employed as competitive and green alternatives in the food packaging
industry.
Keywords: poly(lactic acid), PLA, lignin, nanolignin, composite films, nucleation, mechanical properties, antioxidant activity, food packaging
Published in DKUM: 26.03.2025; Views: 0; Downloads: 1
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2. In-plane deformation behavior and the open area of rotating squares in an auxetic compound fabricPolona Dobnik-Dubrovski, Nejc Novak, Matej Borovinšek, Matej Vesenjak, Zoran Ren, 2022, original scientific article Abstract: A conventional compound fabric was used to develop a modern, multifunctional material
with an auxetic behaviour and a tailored open area for particle filtration. Such material was produced
using traditional textile technology and laser cutting, to induce a rotating squares unit geometry. The
behaviour was investigated of three different rotating unit cell sizes. The laser slit thickness and the
length of the hinges were equal for all three-unit cells. The tensile properties, Poisson’s ratio and
auxetic behaviour of the tested samples were investigated, especially the influence of longitudinal
displacement on the fabric’s open area and the filtered particle sizes (average and maximum). Results
show that the developed compound fabric possesses an average negative Poisson’s ratio of up to
−1, depending on the applied auxetic geometry. The larger rotating cell size samples offer a higher
average negative Poisson’s ratio and a higher breaking strength due to the induced slits. The findings
highlight the usefulness of patterned cuts in conventional textile materials to develop advanced
auxetic textile materials with tailored geometrical and mechanical properties.
Keywords: compound textile material, auxetic structure, open area, filtration, mechanical properties, Poisson’s ratio
Published in DKUM: 25.03.2025; Views: 0; Downloads: 3
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3. Modeling of tensile test results for low alloy steels by linear regression and genetic programming taking into account the non-metallic inclusionsMiha Kovačič, Uroš Župerl, 2022, original scientific article Abstract: Štore Steel Ltd. is one of the biggest flat spring steel producers in Europe. The main
motive for this study was to study the influences of non-metallic inclusions on mechanical properties
obtained by tensile testing. From January 2016 to December 2021, all available tensile strength data
(472 cases–472 test pieces) of 17 low alloy steel grades, which were ordered and used by the final
user in rolled condition, were gathered. Based on the geometry of rolled bars, selected chemical
composition, and average size of worst fields non-metallic inclusions (sulfur, silicate, aluminium
and globular oxides), determined based on ASTM E45, several models for tensile strength, yield
strength, percentage elongation, and percentage reduction area were obtained using linear regression
and genetic programming. Based on modeling results in the period from January 2022 to April 2022,
five successively cast batches of 30MnVS6 were produced with a statistically significant reduction
of content of silicon (t-test, p < 0.05). The content of silicate type of inclusions, yield, and tensile
strength also changed statistically significantly (t-test, p < 0.05). The average yield and tensile strength
increased from 458.5 MPa to 525.4 MPa and from 672.7 MPa to 754.0 MPa, respectively. It is necessary
to emphasize that there were no statistically significant changes in other monitored parameters.
Keywords: mechanical properties, tensile test, tensile strength, yield strength, percentage elongation, percentage reduction area, low alloy steel, modeling, linear regression, genetic programming, industrial study, steel making, optimization
Published in DKUM: 24.03.2025; Views: 0; Downloads: 2
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4. Thermal, molecular dynamics, and mechanical properties of poly(ethylene furanoate)/poly(ε-caprolactone) block copolymersJohan Stanley, Panagiotis A. Klonos, Aikaterini Teknetzi, Nikolaos Rekounas, Apostolos Kyritsis, Lidija Fras Zemljič, Dimitra A. Lambropoulou, Dimitrios Bikiaris, 2024, original scientific article Abstract: This study presents the synthesis and characterization of a series of multiblock copolymers, poly(ethylene 2,5-furandicarboxylate)-poly(ε-caprolactone) (PEF-PCL), created through a combination of the two-step melt polycondensation method and ring opening polymerization, as sustainable alternatives to fossil-based plastics. The structural confirmation of these block copolymers was achieved through Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), ensuring the successful integration of PEF and PCL segments. X-ray Photoelectron Spectroscopy (XPS) was employed for chemical bonding and quantitative analysis, providing insights into the distribution and compatibility of the copolymer components. Differential Scanning Calorimetry (DSC) analysis revealed a single glass transition temperature (Tg), indicating the effective plasticizing effect of PCL on PEF, which enhances the flexibility of the copolymers. X-ray Diffraction (XRD) studies highlight the complex relationship between PCL content and crystallization in PEF-PCL block copolymers, emphasizing the need to balance crystallinity and mechanical properties for optimal material performance. Broadband Dielectric Spectroscopy (BDS) confirmed excellent distribution of PEF-PCL without phase separation, which is vital for maintaining consistent material properties. Mechanical properties were evaluated using Nanoindentation testing, demonstrating the potential of these copolymers as flexible packaging materials due to their enhanced mechanical strength and flexibility. The study concludes that PEF-PCL block copolymers are promising candidates for sustainable packaging solutions, combining environmental benefits with desirable material properties.
Keywords: poly(ethylene furanoate), poly(ε-caprolactone), block copolymers, thermal properties, molecular dynamics, crystallinity, mechanical properties, flexible packaging
Published in DKUM: 13.03.2025; Views: 0; Downloads: 5
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5. Contour maps for simultaneous increase in yield strength and elongation of hot extruded aluminum alloy 6082Iztok Peruš, Goran Kugler, Simon Malej, Milan Terčelj, 2022, original scientific article Abstract: In this paper, the Conditional Average Estimator artificial neural network (CAE ANN) was used to analyze the influence of chemical composition in conjunction with selected process parameters on the yield strength and elongation of an extruded 6082 aluminum alloy (AA6082) profile. Analysis focused on the optimization of mechanical properties as a function of casting temperature, casting speed, addition rate of alloy wire, ram speed, extrusion ratio, and number of extrusion strands on one side, and different contents of chemical elements, i.e., Si, Mn, Mg, and Fe, on the other side. The obtained results revealed very complex non-linear relationships between all of these parameters. Using the proposed approach, it was possible to identify the combinations of chemical composition and process parameters as well as their values for a simultaneous increase of yield strength and elongation of extruded profiles. These results are a contribution of the presented study in comparison with published research results of similar studies in this field. Application of the proposed approach, either in the research and/or in industrial aluminum production, suggests a further increase in the relevant mechanical properties.
Keywords: AA6082, hot extrusion, mechanical properties, yield strength, elongation, artificial neural networks, analysis
Published in DKUM: 12.03.2025; Views: 0; Downloads: 8
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6. Combined effects of metakaolin and hybrid fibers on self-compacting concreteNatalija Bede Odorčić, Gregor Kravanja, 2022, original scientific article Abstract: There is a need to develop new construction materials with improved mechanical performance and durability that are low-priced and have environmental benefits at the same time. This
paper focuses on the rheological, mechanical, morphological, and durability properties of synthetic
and steel fiber reinforced self-compacting concrete (SCC) containing 5–15% metakaolin (M) by mass
as a green replacement for Portland cement. Testing of the fresh mixes included a slump-flow test,
density, and porosity tests. Mechanical properties were determined through compression and flexural
strength. A rapid chloride penetrability test (RCPT) and the chloride migration coefficient were used
to assess the durability of the samples. A scanning electron microscope (SEM) with energy dispersion
spectrometry (EDS) was used to study the concrete microstructure and the interfacial transition zone
(ITZ). The results show that a combination of metakaolin and hybrid fibers has a negative effect on
the flowability of SCC. In contrast, the inclusion of M and hybrid fibers has a positive effect on the
compressive and flexural strength of SCC. The fracture of SCC samples without fibers was brittle
and sudden, unlike the fiber-reinforced SCC samples, which could still transfer a considerable load
with increasing crack mouth opening deflection. Overall, the chloride migration coefficients were
reduced by up to 71% compared to the control mix. The chloride reduction is consistent with the
resulting compact concrete microstructure, which exhibits a strong bond between fibers and the
concrete matrix.
Keywords: self-compacting concrete, synthetic and steel fibers, metakaolin, rheology, mechanical properties, chloride penetration, SEM-EDS
Published in DKUM: 12.03.2025; Views: 0; Downloads: 3
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7. Recent trends in the synthesis of monomers for furanoate polyesters and their nanocomposites’ fabrication as a sustainable packaging materialJohan Stanley, Lidija Fras Zemljič, Dimitra A. Lambropoulou, Dimitrios Bikiaris, 2024, original scientific article Abstract: Furanoate polyesters are an extremely promising new class of materials for packaging applications, particularly furanoate-based nanocomposites, which have gained a high interest level in research and development in both academia and industries. The monomers utilised for the synthesis of furanoate-based polyesters were derived from lignocellulosic biomass, which is essential for both eco-friendliness and sustainability. Also, these polyesters have a lower carbon footprint compared to fossil-based plastics, contributing to greenhouse gas reduction. The furanoate-based nanocomposites exhibit enhanced performance characteristics, such as high thermal stability, excellent mechanical strength, superior barrier resistance, and good bacteriostatic rate, making them suitable for a wide range of industrial applications, especially for food-packaging applications. This paper reviews the recent trends in the synthesis routes of monomers, such as the various catalytic activities involved in the oxidation of 5(hydroxymethyl)furfural (HMF) into 2,5-furandicarboxylic acid (FDCA) and its ester, dimethyl furan-2,5-dicarboxylate (DMFD). In addition, this review explores the fabrication of different furanoate-based nanocomposites prepared by in situ polymerization, by melt mixing or solvent evaporation methods, and by using different types of nanoparticles to enhance the overall material properties of the resulting nanocomposites. Emphasis was given to presenting the effect of these nanoparticles on the furanoate polyester’s properties.
Keywords: 2, 5-furandicarboxylic acid, dimethyl furan-2, 5-dicarboxylat, furanoate polyesters, furanoate nanocomposites, thermal properties, mechanical properties, antibacterial properties, sustainable packaging
Published in DKUM: 10.03.2025; Views: 0; Downloads: 5
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8. Use of Lignin, Waste Tire Rubber, and Waste Glass for Soil StabilizationSüleyman Gücek, Cahit Gürer, Bojan Žlender, Murat V. Taciroğlu, Burak E. Korkmaz, Kürşat Gürkan, Tamara Bračko, Borut Macuh, Rok Varga, Primož Jelušič, 2024, original scientific article Abstract: The complex interactions between soil and additives such as lignin, glass powder, and rubber tires were investigated using principles of material and soil mechanics. Previous research has mainly focused on individual additives in clay soils. In contrast, this study investigates soil improvement with two different types of waste materials simultaneously. The improvement of soil properties by hybrid waste materials was evaluated using several laboratory tests, including the standard Proctor test, the unconfined compressive strength test, the California Bearing Ratio (CBR) test, and cyclic triaxial tests. The aim of this research is to identify key parameters for the design and construction of road pavements and to demonstrate that improving the subgrade with hybrid waste materials contributes significantly to the sustainability of road construction. The mechanical and physical properties were evaluated in detail to determine the optimal mixtures. The results show that the most effective mixture for the combination of waste glass powder and rubber tires contains 20% glass powder and 3% rubber tires, based on the dry weight of the soil. For the combination of waste glass powder and lignin, the optimum mixture consists of 15% glass powder and 15% lignin, based on the dry weight of the soil. These results provide valuable insights into the sustainable use of waste materials for soil stabilization in road construction projects.
Keywords: soil stabilization, waste glass, tire rubber waste, lignin, hybrid waste usage, mechanical
properties, pavement structure
Published in DKUM: 28.02.2025; Views: 0; Downloads: 3
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9. Effect of monomer type on the synthesis and properties of poly(ethylene furanoate)Johan Stanley, Zoi Terzopoulou, Panagiotis A. Klonos, Alexandra Zamboulis, Eleftheria Xanthopoulou, Savvas Koltsakidis, Dimitrios Tzetzis, Lidija Fras Zemljič, Dimitra A. Lambropoulou, Apostolos Kyritsis, George Z. Papageorgiou, Dimitrios Bikiaris, 2023, original scientific article Abstract: This work aimed to produce bio-based poly(ethylene furanoate) (PEF) with a high molecular weight using 2,5-furan dicarboxylic acid (FDCA) or its derivative dimethyl 2,5-furan dicarboxylate (DMFD), targeting food packaging applications. The effect of monomer type, molar ratios, catalyst, polycondensation time, and temperature on synthesized samples’ intrinsic viscosities and color intensity was evaluated. It was found that FDCA is more effective than DMFD in producing PEF with higher molecular weight. A sum of complementary techniques was employed to study the structure– properties relationships of the prepared PEF samples, both in amorphous and semicrystalline states. The amorphous samples exhibited an increase in glass transition temperature of 82–87 ◦C, and annealed samples displayed a decrease in crystallinity with increasing intrinsic viscosity, as analyzed by differential scanning calorimetry and X-ray diffraction. Dielectric spectroscopy showed moderate local and segmental dynamics and high ionic conductivity for the 2,5-FDCA-based samples. The spherulite size and nuclei density of samples improved with increased melt crystallization and viscosity, respectively. The hydrophilicity and oxygen permeability of the samples were reduced with increased rigidity and molecular weight. The nanoindentation test showed that the hardness and elastic modulus of amorphous and annealed samples is higher at low viscosities due to high intermolecular interactions and degree of crystallinity.
Keywords: bio-based polymers, poly(ethylene furanoate), polycondensation, thermal properties, mechanical properties, oxygen transmission rates
Published in DKUM: 13.02.2025; Views: 0; Downloads: 3
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10. Influence of crosslinker on the properties of terpene-based poly(high internal phase emulsion)sRumeysa Beyaz, Stanko Kramer, Burcu Kekevi, Emine Hilal Mert, Irena Pulko, Peter Krajnc, 2024, original scientific article Keywords: terpene, alpha-myrcene, polyHIPE, pore morphology, mechanical properties
Published in DKUM: 03.02.2025; Views: 0; Downloads: 6
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