Search Results (63)

Rammed earth (RE), a traditional material aligned with circular economy (CE) principles, has been gaining renewed interest in contemporary construction due to its low environmental impact and compatibility with sustainable building strategies. Though not a modern invention, it is being reintroduced in response to the increasingly strict European Union (EU) regulations on carbon footprint, life cycle performance, and thermal efficiency. RE walls offer multiple benefits, including humidity regulation, thermal mass, plasticity, and structural strength. This study also draws attention to their often-overlooked ability to mitigate indoor overheating. To preserve these advantages while enhancing thermal performance, this study explores insulation strategies that maintain the vapor-permeable nature of RE walls. A parametric analysis using Delphin 6.1 software was conducted to simulate heat and moisture transfer in two main configurations: (a) a ventilated system insulated with mineral wool (MW), wood wool (WW), hemp shives (HS), and cellulose fiber (CF), protected by a jute mat wind barrier and finished with wooden cladding; (b) a closed system using MW and WW panels finished with lime plaster. In both cases, clay plaster was applied on the interior side. The results reveal distinct hygrothermal behavior among the insulation types and confirm the potential of natural, low-processed materials to support thermal comfort, moisture buffering, and the alignment with CE objectives in energy-efficient construction. Full article

This study presents the development and characterization of electrospun nanofibers composed of polyvinyl alcohol (PVA) and natural beeswax (BW). A stable emulsion containing 9 wt% PVA and 5 wt% BW was successfully formulated and electrospun. The effects of beeswax incorporation on solution properties-viscosity, conductivity, and surface tension—were systematically evaluated. Electrospinning was performed at 30 kV and a working distance of 14.5 cm, yielding nanofibers with diameters between 125 and 425 nm. Scanning electron microscopy (SEM) revealed increased surface roughness and diameter variability in PVA/BW fibers compared to the PVA. Fourier transform infrared spectroscopy (FTIR) confirmed physical incorporation of BW without evidence of chemical bonding. Thermogravimetric and differential scanning calorimetry analyses (TGA/DSC) demonstrated altered behavior and an expanded profile of temperature transitions due to the waxy components. The solubility test of the nanofiber mat in saline indicated that BW slows dissolution and improves the structural integrity of the fibers. This study demonstrates, for the first time, the incorporation of beeswax into electrospun PVA nanofibers with improved structural and thermal properties, indicating potential for further exploration in biomedical material design. Full article

Waste tire textile fiber (WTTF), a secondary product from the processing of end-of-life tires, is predominantly disposed of through incineration or landfilling—both of which present significant environmental hazards. The incineration process emits large quantities of greenhouse gases (GHGs) as well as harmful substances such as dioxins and heavy metals, exacerbating air pollution and contributing to climate change. Conversely, landfilling WTTF results in long-term environmental degradation, as the synthetic fibers are non-biodegradable and can leach pollutants into the surrounding soil and water systems. These detrimental impacts emphasize the pressing need for environmentally sustainable disposal and reuse strategies. We found that 80% of WTTF was used for the production of thermal insulation mats. The other part, i.e., 20% of the raw material, used for the twining, stabilization, and improvement of the properties of the mats, consisted of recycled polyester fiber (RPES), bicomponent polyester fiber (BiPES), and hollow polyester fiber (HPES). The research shows that 80% of WTTF produces a stable filament for sustainable thermal insulating mat formation. The studies on sustainable thermal insulating mats show that the thermal conductivity of the product varies from 0.0412 W/(m∙K) to 0.0338 W/(m∙K). The tensile strength measured parallel to the direction of formation ranges from 5.60 kPa to 13.8 kPa, and, perpendicular to the direction of formation, it ranges from 7.0 kPa to 23 kPa. In addition, the fibers, as well as the finished product, were characterized by low water absorption values, which, depending on the composition, ranged from 1.5% to 4.3%. This research is practically significant because it demonstrates that WTTF can be used to produce insulating materials using non-woven technology. The obtained thermal conductivity values are comparable to those of conventional insulating materials, and the measured mechanical properties meet the requirements for insulating mats. Full article

The push for sustainability in all facets of manufacturing has led to an increased interest in biomass as an alternative to non-renewable materials. Hemp bast fiber mats were produced from a bacterial retting process, named BFM, as the fiber reinforcement. The objective of this study was to evaluate the feasibility of laminating BFM with polylactic acid (PLA) for a composite panel product. Since both BFM and PLA are biodegradable, the resulting BFM-PLA composites will be 100% biodegradable. PLA pallets were processed into thin polymer sheets which served as the matrix. The BFM and PLA plates were laminated in five layers and compression-molded into composite panels. Experiments were conducted on the three BFM-to-PLA ratios (35/65, 45/55, and 50/50). Mechanical properties (tensile and bending properties) and physical properties (thickness swell and water absorption) were tested and compared to the currently commercial sheet molding compound (SMC) from fiber glass. The thermal behavior of the BFM/PLA composites was characterized using dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The developed BFM/PLA composite product is a sustainable alternative to existing synthetical fiber-reinforced polymer (FRP) that is biodegradable in landfill at the end of life. Full article

Sustainability requirements must be met by the appropriate selection of efficient and environmentally friendly materials and processes. We present materials obtained via all-in-water methods: first, few-layer graphene (FLG)–polyvinyl alcohol (PVA) colloids and then electrospun PVA-FLG fibers. The effects of the FLG concentration, and indirectly of ultrasound, are reflected via the modification of the structural and physical properties, including the microstructure, viscosity, thermal degradation and mechanical properties, of colloids and fiber mats. The primary results are highly encouraging for further optimization and the development of conductive, and mechanically resistant, materials. Full article

The extensive utilization of lithium-ion (Li-ion) batteries within the automotive industry necessitates rigorous measures to ensure their mechanical robustness, crucial for averting thermal runaway incidents and ensuring vehicle safety. This paper introduces an innovative methodology aimed at homogenizing the mechanical response of Li-ion batteries under compression load, using Finite Element Method (FEM) techniques to improve computational efficiency. A novel approach is proposed, involving the selective application of compression loads solely to the Jelly Roll and its casing, achieved by cutting the battery heads. Through this method, distinct mechanical behaviors are identified within the battery force displacement curve: an elastic region, a zone characterized by plastic deformation, and a segment exhibiting densification. By delineating these regions, our study facilitates a comprehensive understanding of the battery’s mechanical response under compression. Two battery models were employed in this study: one representing the battery as a solid volume, and another featuring the jelly roll as a solid volume enclosed by a shell representing the casing. The material utilized was LS Dyna MAT24, chosen for its piecewise characteristics’ definition, and its validation was primarily conducted through the curve fitting method applied to the force–displacement curve, taking in account the three regions of the compression force behavior. This approach not only optimizes computational resources but also offers insights crucial for enhancing the mechanical stability of Li-ion batteries in automotive applications. Full article

Building envelopes with natural fibers are the future of sustainable construction, combining ecology and energy efficiency. The geopolymer building envelope was reinforced with innovative composite bars and two types of natural insulation (coconut mats and flax/hemp non-woven fabrics) were used as the core material. A 10 mol sodium hydroxide solution with an aqueous sodium silicate solution was used for the alkaline activation of the geopolymers. The purpose of this study was to confirm the feasibility of producing geopolymer composites with insulating layers made of renewable materials, which would have compressive strengths like those of C25/30-grade concrete and thermal conductivity coefficients like those of lightweight concrete. This publication presents the results of physicochemical tests on the base materials (oxide (XRF) and mineral phase (XRD) analysis as well as morphology and EDS) and studies the physical (density measurements), mechanical (flexural and compressive strength tests) and insulating properties (thermal conductivity measurements) of the finished sandwich partitions. The composites achieved a flexural strength of 7 MPa, a compressive strength of up to 30 MPa and a decrease in the thermal conductivity coefficient of about 60%. The research demonstrates contribution to sustainable construction by developing geopolymer composites, offering both structural integrity and superior thermal insulation. This innovation not only reduces reliance on traditional, carbon-intensive materials but also promotes the use of eco-friendly resources, significantly lowering the carbon footprint of construction. The integration of natural fibers into geopolymer matrices addresses key environmental concerns, advancing a rapidly growing field that aligns with global efforts toward energy efficiency, waste reduction, and circular economy principles in building design. Full article

No matter where we reside, the issue of greenhouse gas emissions impacts us all. Their influence has a disastrous effect on the earth’s climate, producing global warming and many other irreversible environmental impacts, even though it is occasionally invisible to the independent eye. Phase change materials (PCMs) can store and release heat when it is abundant during the day (e.g., from solar radiation), for use at night, or on chilly days when buildings need to be heated. As a consequence, buildings use less energy to heat and cool, which lowers greenhouse gas emissions. Consequently, research on thermally active medium-density fiberboard (MDF) with PCMs is presented in this work. MDF is useful for interior design and furniture manufacturing. The boards were created using pine (Pinus sylvestris L.) and spruce (Picea abies L.) fibers, urea–formaldehyde resin, and PCM powder, with a phase transition temperature of 22 °C, a density of 785 kg m⁻³, a latent heat capacity of 160 kJ kg⁻¹, a volumetric heat capacity of 126 MJ m⁻³, a specific heat capacity of 2.2 kJ kgK⁻¹, a thermal conductivity of 0.18 W mK⁻¹, and a maximum operating temperature of 200 °C. Before resination, the wood fibers were divided into two outer layers (16%) and an interior layer (68% by weight). Throughout the resination process, the PCM particles were solely integrated into the inner layer fibers. The mats were created by hand. A hydraulic press (AKE, Mariannelund, Sweden) was used to press the boards, and its operating parameters were 180 °C, 20 s/mm of nominal thickness, and 2.5 MPa for the maximum unit pressing pressure. Five variants of MDF with a PCM additive were developed: 0%, 5%, 10%, 30%, and 50%. According to the study, scores at the MOR, MOE, IB, and screw withdrawal resistance (SWR) tests decreased when PCM content was added, for example, MOE from 3176 to 1057 N mm⁻², MOR from 41.2 to 11.5 N mm⁻², and IB from 0.78 to 0.27 N mm⁻². However, the results of the thickness swelling and water absorption tests indicate that the PCM particles do not exhibit a substantial capacity to absorb water, retaining the dimensional stability of the MDF boards. The thickness swelling positively decreased with the PCM content increase from 15.1 to 7.38% after 24 h of soaking. The panel’s thermal characteristics improved with the increasing PCM concentration, according to the data. The density profiles of all the variations under consideration had a somewhat U-shaped appearance; however, the version with a 50% PCM content had a flatter form and no obvious layer compaction on the panel surface. Therefore, certain mechanical and physical characteristics of the manufactured panels can be enhanced by a well-chosen PCM addition. Full article

In this study, we quantitatively investigate the impact of 1.4 wt.% chromium and 1.4 wt.% molybdenum additions on pearlitic microstructure characteristics in 1 wt.% carbon steels. The study was carried out using a combination of experimental methods and phase field simulations. We utilized MatCalc v5.51 and JMatPro v12 to predict transformation behaviors, and electron microscopy for microstructural examination, focusing on pearlite morphology under varying thermal conditions. Phase field simulations were carried out using MICRESS v7.2 software and, informed by thermodynamic data from MatCalc v5.51 and the literature, were conducted to replicate pearlite formation, demonstrating a good agreement with the experimental observations. In this work, we introduced a semi-automatic reliable microstructural analysis method, quantifying features like lamella dimensions and spacing through image processing by Fiji ImageJ v1.54f. The introduction of Cr resulted in longer, thinner, and more homogeneously distributed cementite lamellae, while Mo led to shorter, thicker lamellae. Phase field simulations accurately predicted these trends and showed that alloying with Cr or Mo increases the density and circularity of the lamellae. Our results demonstrate that Cr stabilizes pearlite formation, promoting a uniform microstructure, whereas Mo affects the morphology without enhancing homogeneity. The phase field model, validated by experimental data, provides insights into the morphological changes induced by these alloying elements, supporting the optimization of steel processing conditions. Full article

Essential oils have been identified as effective natural compounds to prevent bacterial infections and thus are widely proposed as bioactive agents for biomedical applications. Across the literature, various essential oils have been incorporated into electrospun fibres to produce materials with, among others, antibacterial, anti-inflammatory and antioxidant activity. However, limited research has been conducted so far on the effect of these chemical products on the physical characteristics of the resulting composite fibres for extended periods of time. Within this work, electrospun fibres of poly(lactic acid) (PLA) were loaded with the essential oil limonene, and the impact of storage conditions and duration (up to 12 weeks) on the thermal degradation, glass transition temperature and mechanical response of the fibrous mats were investigated. It was found that the concentration of the encapsulated limonene changed over time and thus the properties of the PLA–limonene fibres evolved, particularly in the first two weeks of storage (independently from storage conditions). The amount of limonene retained within the fibres, even 4 weeks after fibre generation, was effective to successfully inhibit the growth of model microorganisms Escherichia coli, Staphylococcus aureus and Bacillus subtilis. The results of this work demonstrate the importance of evaluating physical properties during the ageing of electrospun fibres encapsulating essential oils, in order to predict performance modification when the composite fibres are used as constituents of medical devices. Full article

This study addresses the challenge of enhancing the transverse mechanical properties of oriented polyacrylonitrile (PAN) nanofibers, which are known for their excellent longitudinal tensile strength, without significantly compromising their inherent porosity, which is essential for effective filtration. This study explores the effects of doping PAN nanofiber composites with varying concentrations of polyvinyl alcohol (PVA) (0.5%, 1%, and 2%), introduced into the PAN matrix via a dip-coating method. This approach ensured a random distribution of PVA within the nanofiber mat, aiming to leverage the synergistic interactions between PAN fibers and PVA to improve the composite’s overall performance. This synergy is primarily manifested in the structural and functional augmentation of the PAN nanofiber mats through localized PVA agglomerations, thin films between fibers, and coatings on the fibers themselves. Comprehensive evaluation techniques were employed, including scanning electron microscopy (SEM) for morphological insights; transverse and longitudinal mechanical testing; a thermogravimetric analysis (TGA) for thermal stability; and differential scanning calorimetry (DSC) for thermal behavior analyses. Additionally, a finite element method (FEM) analysis was conducted on a numerical simulation of the composite. Using our novel method, the results demonstrated that a minimal concentration of the PVA solution effectively preserved the porosity of the PAN matrix while significantly enhancing its mechanical strength. Moreover, the numerical simulations showed strong agreement with the experimental results, validating the effectiveness of PVA doping in enhancing the mechanical properties of PAN nanofiber mats without sacrificing their functional porosity. Full article

Maltodextrins are products of starch hydrolysis that can be processed into dry fibres through electrospinning and subsequently cured via mild thermal treatment to obtain nonwoven cross-linked polysaccharide-based mats. The sustainability of the process and the bioderived nature make this class of materials suitable candidates to be studied as renewable sorbents for the removal of contaminants from water. In this work, electrospinning of water solutions containing 50% wt. of commercial maltodextrin (Glucidex 2^®) and 16.6% wt. of citric acid was carried out at 1.2 mL/h flow and 30 kV applied voltage, followed by thermal curing at 180 °C of the dry fibres produced to obtain cross-linked mats. Well-defined fibres with a mean diameter of 1.64 ± 0.35 µm were successfully obtained and characterised by scanning electron microscopy, thermogravimetric analysis, and attenuated total reflectance Fourier transform infrared spectroscopy. Afterwards, a series of sorption tests were conducted to evaluate the effectiveness of the mats in removing atenolol from water. The results of the batch tests followed by HPLC-UV/Vis showed high sorption rates, with over 90% of the atenolol removed, and a maximum removal capacity of 7 mg/g. Furthermore, continuous fixed-bed sorption tests proved the positive interaction between the polymers and atenolol. Full article

Carbon nanofiber (CNF) films or mats have great conductivity and thermal stability and are widely used in different technological processes. Among all the fabrication methods, electrospinning is a simple yet effective technique for preparing CNF mats, but the electrospun CNF mats are often brittle. Here, we report a feasible protocol by which to control the alignment of carbon black nanoparticles (CB NPs) within CNF to enhance the flexibility. The CB NPs (~45 nm) are treated with non-ionic surfactant Triton-X 100 (TX) prior to being blended with a solution containing poly(vinyl butyral) and polyacrylonitrile, followed by electrospinning and then carbonization. The optimized CB-TX@CNF mat has a boosted elongation from 2.25% of pure CNF to 2.49%. On the contrary, the untreated CB loaded in CNF displayed a lower elongation of 1.85% because of the aggregated CB spots created weak joints. The controlled and uniform dispersion of CB NPs helped to scatter the applied bending force in the softness test. This feasible protocol paves the way for using these facile surface-treated CB NPs as a commercial reinforcement for producing flexible CNF films. Full article

The aim of this study is to reduce the manufacturing cost of a hydrophobic and heat-insulating silica aerogel and promote its industrial application in the field of thermal insulation. Silica aerogels with hydrophobicity and thermal-insulation capabilities were synthesized by using water-glass as the silicon source and supercritical drying. The effectiveness of acid and alkali catalysis is compared in the formation of the sol. The introduction of sodium methyl silicate for the copolymerization enhances the hydrophobicity of the aerogel. The resultant silica aerogel has high hydrophobicity and a mesoporous structure with a pore volume exceeding 4.0 cm³·g⁻¹ and a specific surface area exceeding 950 m²·g⁻¹. The obtained silica aerogel/fiber-glass-mat composite has high thermal insulation, with a thermal conductivity of less than 0.020 W·m⁻¹·K⁻¹. The cost-effective process is promising for applications in the industrial preparation of silica aerogel thermal-insulating material. Full article

This study investigated the influence of fiber content, temperature, and relative humidity on the thermal insulation properties of nonwoven mats made of seed fibers from Asclepias Syriaca, commonly known as milkweed floss. Nonwoven mats with a 1-inch thickness were produced by uniformly arranging milkweed fibers within a mold. Various quantities of fiber were employed to obtain nonwoven mats with a fiber content ranging from 5 to 35 kg/m³. Thermal conductivity and thermal diffusivity were measured across diverse relative humidity levels and temperatures. Simultaneously, milkweed floss samples were exposed to identical environmental conditions to assess the moisture regain and specific heat capacities of the fiber. The specific heat capacity of milkweed and thermal conductivity of the nonwovens exhibited a linear increase with temperature. The thermal diffusivity and thermal conductivity of the nonwovens decreased with rising fiber content. The thermal insulation properties of the nonwovens remained partially stable below 30% relative humidity but substantially deteriorated at higher levels. The nonwovens exhibited optimal thermal insulation properties at a fiber content between 20 and 25 kg/m³. The results of this study highlighted several technical advantages of employing milkweed floss as a sustainable and lightweight solution for thermal insulation. Full article