Search Results (48)

Ice accumulation poses a significant hazard to aviation safety, particularly in cold weather conditions, as it can compromise aerodynamic performance, increase structural weight, and diminish lift, occasionally resulting in severe stall incidents. At present, such risks are managed through the use of energy-demanding active ice protection systems (IPSs), which operate either by inhibiting ice formation (anti-icing) or by removing existing ice (de-icing). Nonetheless, in the context of future sustainable aviation, there is a pressing need to develop IPSs with lower energy requirements. A promising approach involves hybrid IPSs that integrate conventional active systems with passive superhydrophobic or icephobic surface treatments, which are capable of preventing, delaying, or minimizing ice buildup. These systems offer the potential to substantially decrease the energy consumption and consequently the CO₂ emissions. Furthermore, in accordance with FAA regulations, active IPSs are not permitted to operate during takeoff and initial flight stages to prevent any reduction in engine thrust. These two reasons emphasize the critical importance of developing efficient coatings that, on the one hand, promote the mobility of water droplets, hereby preventing ice formation, as achieved by superhydrophobic surfaces, and on the other hand, facilitate ice detachment, as required for icephobic performance. In this context, the primary objective of the present work is to emphasize the icephobic properties of two superhydrophobic coatings. To achieve this, an extensive characterization is first conducted, including wettability, Surface Free Energy (SFE), and surface roughness, to confirm their superhydrophobic nature. This is followed by an assessment of their icephobic performance, specifically in terms of ice adhesion strength, with comparisons made against a commercial aeronautical coating. The results revealed a significant reduction in both the wettability and SFE of the developed coatings compared to the reference, along with a marked decrease in ice adhesion strength, thereby demonstrating their icephobic properties. Future activities will focus on the combination of coatings with active IPS in order to assess the energy efficiency under extensive icing conditions where both superhydrophobic and icephobic properties are required. Full article

The growing demand for sustainable energy solutions has intensified research on phase change materials (PCMs) due to their ability to efficiently store and release thermal energy. However, traditional PCMs are often made from petroleum-derived materials or rely on processes that pose environmental concerns. The aim of this work is therefore to explore the development and use of sustainable organic PCMs, in particular those based on bio-based or waste-derived materials. Bio-based PCMs, including fatty acids, natural waxes, and biopolymers, are in fact characterized by renewability and biodegradability. Waste-derived PCMs, such as those from the lost-wax casting industry and industrial by-products, offer an environmentally friendly approach to energy storage by reusing waste materials. This paper aims to analyze the thermal, mechanical, and in-service performance of these sustainable materials, highlighting their advantages and limitations compared to the most widely used commercial PCMs. Furthermore, recent progress in the integration of sustainable PCMs into building materials is illustrated to assess their practical implementation. Challenges and limitations, as well as possible solutions and future research directions, are also discussed. Full article

The high global energy demand drives the search for sustainable alternatives for energy production and storage. Among the most effective solutions are phase change materials (PCMs). In particular, organic PCMs offer a high capacity to store and release thermal energy in response to external thermal variations, even over a wide temperature range. They find profitable applications in various sectors, from construction to electronics, offering flexibility and considerable energy storage according to need. In the search for new and effective PCMs, reusing by-products from different industries would offer both economic and environmental benefits. With this goal in mind, several organic PCMs with different characteristics and origins were analyzed in the present study. Two of them were by-products of the lost wax casting industry. In fact, we wanted to verify whether this waste could be employed as an effective, low-cost PCM. For comparison purposes, two commercial PCMs were selected, namely a paraffin and a microencapsulated PCM. Finally, a PCM blend was produced by mixing a commercial PCM and a waxy by-product. The five selected or developed PCMs were subjected to different tests to investigate their chemical composition, thermal characteristics, and thermal stability before and after repeated (i.e., 100) cycles of melting and crystallization processes. The results demonstrated that the durability of the non-commercial PCMs with regard to thermal loads was not inferior, and was in some cases even superior, to commercial PCMs. This study therefore proposes an innovative path to reuse the by-products of different production processes to support the environment. Full article

The development of construction materials with the integration of phase change materials (PCMs) has been a topic of wide interest in the scientific community, especially in recent years, due to its positive impact on temperature regulation inside buildings. However, little is known about the behavior of materials doped with PCMs when exposed to accidental or severe environments. Currently, a large area of the planet experiences seasonal freeze–thaw effects, which impact the durability and performance of construction materials. Accordingly, the main objective of this study was to evaluate the damage caused by cyclic freeze–thaw actions on the behavior of a cement mortar, including a PEG-based form-stable PCM. An experimental methodology was developed based on the physical and mechanical characterization of mortars under normal operating conditions and after being subjected to freeze–thaw cycles. The results indicated that, under normal exposure conditions, the incorporation of aggregate functionalized with PCM led to a decrease in the mortar’s water absorption capacity, compressive strength, and adhesion. However, its applicability has not been compromised. Exposure to freeze–thaw cycles caused a loss of mass in the specimens and a decrease in the compressive strength and adhesion capability of the mortar. Full article

The development of 3D porous nanocarbon composites has improved the performance of piezoresistive sensors. However, the functionalization and surface distribution of nanocarbon may limit conductivity and mechanical stability. In this study, a mechanochemical approach was developed to create an elastomeric/CNTs 3D porous nanocomposite. By changing parameters such as CNT length and polymer amount, different composites with improved piezoresistive properties can be produced for wearables or fluidic devices. The material can withstand compressive stress up to 150 Kpa and has a sensitivity of up to 330 Kpa⁻¹ and a limit of detection of 0.2 Pa and 50 nm for pressure and extension, respectively. Full article

This research study focused on the effect of adding boric acid to epoxy resin in order to obtain a composite material with improved properties and performance. To this end, a fine powder of boric acid (H₃BO₃) was introduced into epoxy resin in different amounts, i.e., 0.5 g, 1.0 g, and 1.5 g. As the matrix of the epoxy composites, styrene-modified epoxy resin based on bisphenol A (BPA) (Epidian 53) was used. It was cross-linked with two types of curing agents, i.e., an amine (ET) and a polyamide (PAC). The mechanical properties of the obtained epoxy composites (in terms of compressive strength, compressive modulus, and compressive strain) were determined at room temperature in order to assess the effect of the addition of boron acid and of the type of curing agent employed to cure the epoxy on these characteristics. Calorimetric measurements were made to highlight any changes in the glass transition temperature (Tg) as a result of the addition of boric acid to epoxy resin. Finally, flammability tests were performed on both Epidian 53/PAC and Epidian 53/ET epoxy composites to analyze their fire behavior and consequently establish the effectiveness of the selected additive as a flame retardant. Full article

The construction sector’s pursuit of sustainability, driven by growing concerns about climate change and resource depletion, requires innovative solutions to reduce the energy consumption necessary to ensure thermal comfort in buildings. The introduction of phase change materials (PCMs) in construction elements represents an effective solution to these problems. PCMs are, in fact, able to regulate internal temperature by storing and releasing thermal energy during their phase transitions. In particular, polyethylene glycol (PEG)-based organic PCMs offer high heat storage capacity, compatibility with building materials, and minimal environmental impact. They are often used in building applications incorporated in an inert matrix, using the “form-stable method”. This article critically examines various matrices proposed in the existing literature to realize PEG-based PCMs, with the aim of analyzing their influence on the final characteristics of any PCM. In addition, an attempt to correlate the quantity of PEG with the heat stored and released by the PCM is presented, using a linear regression model applied to groups of matrices of the same chemical nature. The results of these analyses would, in fact, provide useful indications for an optimal choice of the PEG/matrix system capable of responding to specific application needs, particularly in the building sector. Full article

The aim of this research was a comparative analysis of selected mechanical properties of epoxy compounds that were modified with metallic fillers and aged in aqueous environments. The tested epoxy compounds consisted of three components: styrene modified epoxy resin based on Bisphenol A, triethylenetetramine curing agent (resin/curing agent ratio of 100:10) and two types of metallic fillers in the form of particles: aluminum alloy (EN AW-2024–AlCu4Mg1) and tin-phosphor bronze (CuSn10P). Samples were subjected to ageing in 4 water environments: low-, medium- and high-mineralized natural water and in a sugar-containing solution for 1, 2 and 3 months. The epoxy samples were subjected to compressive strength tests in accordance with the ISO 604:2002 standard. It was observed that, among others, the compositions seasoned in low-mineralized water usually achieved the highest average compressive strength. As for filler type, using the bronze filler (CuSn10P) usually achieved the highest average compressive strength results. Full article

The widespread use of synthetic plastics, as well as the waste produced at the end of their life cycle, poses serious environmental issues. In this context, bio-based plastics, i.e., natural polymers produced from renewable resources, represent a promising alternative to petroleum-based materials. One potential source of biopolymers is waste from the food industry, the use of which also provides a sustainable and eco-friendly solution to waste management. Thus, the aim of this work concerns the extraction of polysaccharide fractions from lemon, tomato and fennel waste. Characterizing the chemical–physical and thermodynamic properties of these polysaccharides is an essential step in evaluating their potential applications. Hence, the solubility of the extracted polysaccharides in different solvents, including water and organic solvents, was determined since it is an important parameter that determines their properties and applications. Also, acid-base titration was carried out, along with thermoanalytical tests through differential scanning calorimetry. Finally, the electrospinning of waste polysaccharides was investigated to explore the feasibility of obtaining polysaccharide-based membranes. Indeed, electrospun fibers are a promising structure/system via which it is possible to apply waste polysaccharides in packaging or well-being applications. Thanks to processing feasibility, it is possible to electrospin waste polysaccharides by combining them with different materials to obtain porous 3D membranes made of nanosized fibers. Full article

The construction industry is responsible for high energetic consumption, especially associated with buildings’ heating and cooling needs. This issue has attracted the attention of the scientific community, governments and authorities from all over the world, especially in the European Union, motivated by recent international conflicts which forced the countries to rethink their energy policies. Over the years, energy consumption has been based on non-renewable energy sources such as natural gas, oil and coal. Nowadays, it is urgent to implement solutions that aim to minimize these high energetic consumptions and act based on clean and renewable energy sources. In recent years, phase change materials (PCM) have become an area of high interest and development, since they allow to minimize the energy consumption in buildings, based in solar energy, due to their thermal storage capacity. The main objective of this work consists of a perspective of the evolution of the development and application of thermal storage technology through the incorporation of PCM in the construction sector, focusing on the last 10 years of research, showing the most recent developments of its application in construction materials, such as mortars, concrete, incorporation in porous aggregates, naturally based materials, carbon-based materials, boards, blocks and solar thermal systems. Full article

The aim of this work was to study the valorization of argan seed pulp, a waste material obtained from argan oil extraction, for the biosynthesis of polyhydroxybutyrate (PHB). A new species that showed the metabolic capacity for the conversion of argan waste into the bio-based polymer was isolated from an argan crop located in Teroudant, a southwestern region of Morocco, where the arid soil is exploited for goat grazing. The PHB accumulation efficiency of this new species was compared to the previously identified species 1B belonging to the genus Sphingomonas, and results were reported as dry cell weight residual biomass and PHB final yield measured. Temperature, incubation time, pH, NaCl concentration, nitrogen sources, residue concentrations, and culture medium volumes were analyzed with the aim of obtaining a maximum accumulation of PHB. UV-visible spectrophotometry and FTIR analysis confirmed that PHB was present in the material extracted from the bacterial culture. The results of this wide investigation indicated that the new isolated species 2D1 had a higher efficiency in PHB production compared to the previously identified strain 1B, which was isolated from a contaminated argan soil in Teroudant. PHB final yield of the two bacterial species, i.e., the new isolated and 1B, cultivated under optimal culture conditions, in 500 mL MSM enriched with 3% argan waste, were 21.40% (5.91 ± 0.16 g/L) and 8.16% (1.92 ± 0.23 g/L), respectively. For the new isolated strain, the result of the UV-visible spectrum indicates the absorbance at 248 nm, while the FTIR spectrum showed peaks at 1726 cm⁻¹ and 1270 cm⁻¹: these characteristic peaks indicated the presence of PHB in the extract. The data from the species 1B UV-visible and FTIR spectra were previously reported and were used in this study for a correlation analysis. Furthermore, additional peaks, uncharacteristic of standard PHB, suggest the presence of impurities (e.g., cell debris, solvent residues, biomass residues) that persisted after extraction. Therefore, a further enhancement of the sample purification during extraction is recommended for more accuracy in the chemical characterization. If 470,000 tons of argan fruit waste can be produced annually, and 3% of waste is consumed in 500 mL culture by 2D1 to produce 5.91 g/L (21.40%) of the bio-based polymer PHB, it can be estimated that the amount of putative PHB that can be extracted annually from the total argan fruit waste is about 2300 tons. Full article

The growing concern for the environment and the depletion of raw materials such as fossil fuels is driving research towards the exploitation of new materials and the development of new technologies. Phase-change materials (PCMs) are increasingly used to reduce the energy required for the heating/cooling of buildings. The biggest challenge is to find a PCM with suitable characteristics able to meet the needs of the different climates in which it is placed. The originality of our research, therefore, lies in the possibility of selecting the most appropriate polymer to produce a PCM suitable for different climatic conditions that characterize the area in which a building is located. Furthermore, the proposed form-stable PCMs were obtained by including low-toxic, low-flammability polymers in waste stone fragments, according to the principles of a circular economy. These original sustainable PCMs were then used as aggregates by adding them to mortars (based on air lime, hydraulic lime, cement and gypsum). The mortars containing the PCMs were analyzed in fresh (workability) and hardened (flexural and compressive strengths and thermal characteristics) states. The results obtained showed that although the inclusion of PCM reduced the mechanical properties of the mortars, good mechanical properties can be still achieved by using an adequate binder content. The produced mortars were also analyzed by thermal analysis to assess how the addition of a PEG-based PCM affected their thermal behavior. The original PCMs were proven to be effective in improving the indoor temperature when included in mortars applied as plasters. Full article

Polyhydroxybutyrate (PHB) is a biodegradable bio-based polymer synthesized by microorganisms under unfavorable conditions from agro-industrial residues as a source of carbon. These aspects make the bio-based polymer attractive for the mass production of biodegradable plastics, and a definitive replacement for petroleum-based plastics. The aim of this work was to characterize the putative PHB-producing bacterium 1B isolated from the argan soil, to identify the polymer produced, and quantify the PHB production using argan seeds waste. DNA extraction, PCR, and Sanger sequencing were conducted for the molecular identification of strain 1B; the residual biomass and the PHB quantification were measured and compared in the presence of simple sugars and pretreated argan seeds waste. The 1B growth and PHB synthesis were optimized by selecting physical and nutritional parameters: temperature, incubation time, pH, NaCl concentration, and nitrogen sources concentrations. A preliminary characterization of the bio-based polymer extracted was conducted by UV-Visible spectrophotometry and FTIR analysis. The strain 1B was identified as belonging to the genus Sphingomonas. The PHB final yield was higher in a growth culture enriched with argan waste (3.06%) than with simple sugars. The selected conditions for the bacterial optimal growth incremented the PHB final yield to 6.13%, while the increase in the argan residue concentration from 1 to 3% in a larger culture volume led to the PHB final yield of 8.16%. UV-Visible spectrophotometry of the extracted sample reported a remarkable peak at 248 nm, as well as FTIR spectra analysis, showed peaks at 1728 and 1282 wavenumber/cm. Both preliminary characterizations demonstrated that the extracted sample is the bio-based polymer polyhydroxybutyrate. The results reported in this work reveal how the costless available argan seeds can be used for polyhydroxybutyrate production using a novel Sphingomonas species. Full article

The durability of reinforced concrete strongly depends on the environment in which it is located; in any case, the concrete and the reinforcing bars it contains are constantly subject to slow deterioration processes. The protection of concrete structures is, therefore, essential to increase their service life, reducing the costs for their repair and maintenance. The commercial widely used coatings are mainly based on petroleum derivatives (i.e., resins, solvents): increased sensitivity and attention to human health and the protection of the environment pressed research to find alternatives to synthetic products, identifying safer materials with a low environmental impact to employ as protective coatings. In this review, new sustainable products already used or potentially suitable to act as protective treatments for concrete were analyzed and presented. These are natural (bio-based) or waste materials, in which the use of synthetic resins and hazardous solvents, for humans and the environment, are minimized, exploiting waste materials or by-products of other processes, if possible. The main properties and characteristics of these new products are illustrated, highlighting the potential advantages over commercial products also in terms of performance. Full article

The aim of this work was to investigate selected biological and toxicity properties of cured epoxy resin-based compounds based on a bisphenol A epoxy resin, cold-cured by a polyamide and containing two types of metal powders (aluminum and copper). This study involved cytotoxicity analysis, pH measurements, absorbance measurements and sterilization. The cytotoxicity analysis was conducted to determine the harmful degree of the cured epoxy resin. Aimed at identifying toxic agents in cured compounds, the cytotoxicity analysis involved absorbance measurements in an entire wavelength range. Cytotoxicity and absorbance results demonstrated that the extracts of all the tested resin samples had no cytotoxic effects on the cells of living organisms. The absorbance values obtained over the entire wavelength range did not point to the formation of aggregations, which proved that no toxic agents harmful to living organisms were extracted from the resin samples. Based on the results obtained, it can be concluded that all tested compounds, based on epoxy resins, which are also used as adhesives in various applications, are essentially safe materials when using such formulations in a cured state. Full article