Search Results (222)

Today, the search for resources related to non-fossil raw materials that require less carbon-based energy consumption, use less water, and produce recyclable waste is prevailing. In the future, will this effort be replaced by resources sufficient to be produced in environmentally friendly ways? Resources will be circulated in a controlled manner, and materials will be sustainable. Most of the energy sources will be sustainable, derived from natural resources (sun, wind, waves, geothermal sources, etc.). The world will be managed by data, enabling resource sufficiency. Sustainable development is therefore a long-term strategy including economic, human (social), and environmental (material) resources. This strategy requires development in the complex identification and quantification of waste of different origins, including plastics and fibers. The identification of polymer complex mixtures and fibrous-blend waste, including microplastics, is a fundamental tool for effective environmental monitoring and comprehensive recycling management. Raman spectroscopy, combined with spectral unmixing techniques, provides a powerful tool for resolving overlapping spectral components and characterizing the composition of fibrous polymeric materials. The general goal of hyperspectral unmixing is to decompose an observed spectral mixture matrix into a set of pure component spectra and their respective portions (contributions or abundance) or ideally concentrations. This requires solving an inverse problem under physical and mathematical constraints. Principal component analysis (PCA), based on singular value decomposition (SVD), followed by independent component analysis (ICA) rotation, is used to reduce the number of components to a meaningful set of endmembers. The extracted endmembers should be statistically independent, nonnegative, and sum to one, because they represent real chemical components in the mixture. These requirements are fulfilled by constrained quadratic programming using the Newton linearization method. The RAMIX program, based on these procedures, has already been described, and its source code is available in another article written in Python. It is designed for the analysis of experimental Raman spectra of polymeric mixtures and for mapping waste fibrous blends. This program is used here for Raman spectral analysis of compressed textile samples composed of different staple fiber types. To evaluate Raman spectra, a simple, cost-effective, custom-built measurement system was created. This system allows mapping of fibrous mixtures by Raman spectra across a line or an area. Full article

Wearable sweat biosensors require electrode materials with high surface area, conductivity and mechanical compliance, yet chemically polymerized polyaniline forms dense, low-surface-area films with limited flexibility. In this work, flexible free-standing nanofiber mats were fabricated by coaxial electrospinning, using a sulfuric-acid-doped polyacrylonitrile/polyaniline (PAN/PANI) core and a shell containing graphene oxide nanoscrolls (GONS) at 1 and 3 wt%, followed by gold nanoparticle and ferrocene incorporation, glucose oxidase (GOx) immobilization and a Nafion coating. Scanning electron microscopy showed uniform bead-free fibers with an interconnected pore network and an apparent image-derived porosity of approximately 40%. Energy-dispersive X-ray spectroscopy confirmed the uniform distribution of carbon, oxygen, nitrogen and sulfur across the matrix. Fourier-transform infrared spectroscopy retained the nitrile band at 2243 cm⁻¹ and the quinoid and benzenoid bands at 1547 and 1476 cm⁻¹, while amide bands at 1730 and 1641 cm⁻¹ confirmed retention of protein from enzymes. X-ray diffraction gave crystallinities of 76.6% for GONS and 60% for the pure PANI. Four-point probe measurements showed conductivity increasing from 0.0481 S/cm to 1 wt% GONS to 0.0595 S/cm for the 3 wt% mat with additives. These material and structural characterizations establish a promising foundation for future electrochemical validation and sensor development. Full article

Fiber-reinforced cementitious composites have become increasingly important in the development of durable and sustainable construction materials, particularly following the replacement of asbestos-based reinforcements. However, the long-term performance of these composites is strongly influenced by the characteristics of the fiber–matrix interface, where moisture transport, interfacial degradation, and stress transfer mechanisms govern durability and mechanical behavior. Consequently, considerable efforts have been devoted to developing surface engineering strategies capable of improving fiber–matrix compatibility and enhancing composite performance. This review examines recent advances in surface modification and interfacial engineering approaches applied to fiber-reinforced cementitious composites. The discussion covers fiber–matrix bonding mechanisms and the main modification strategies, including alkali treatments, hornification, silane coupling agents, polymeric and hydrophobic coatings, nanomaterial-assisted modifications, and carbonation-induced surface engineering. The effects of these approaches on interfacial properties, durability, dimensional stability, and mechanical performance are critically assessed. The literature indicates that treatments combining surface chemistry modification, moisture control, and mineral-based densification provide more consistent improvements in durability than single-mechanism approaches. Future developments are expected to focus on scalable treatment methods, low-carbon cementitious systems, and advanced materials design strategies, enabling the development of next-generation fiber cement composites with enhanced durability, sustainability, and long-term performance. Full article

Polybenzoxazines (PBz) represent a versatile class of high-performance thermosetting polymers that have attracted significant attention for advanced composite applications due to their unique combination of properties including high glass transition temperatures, low polymerization shrinkage, excellent thermal stability, and molecular design flexibility. This comprehensive review examines the structure–property relationships governing PBz composite performance, from molecular design principles through network formation, composite reinforcement strategies, and ultimate application performance. The review systematically addresses benzoxazine monomer structure and its influence on polymer network architecture, explores the polymerization mechanism, and critically evaluates composite design strategies incorporating carbon-based nanofillers, fiber reinforcements, and hybrid filler systems. Detailed analysis of structure–property relationships reveals how molecular and composite architecture control thermal stability (glass transition temperatures exceeding 350 °C and char yields up to 92%), mechanical performance, electrical properties (dielectric constants as low as 2.67), and chemical durability. Processing techniques ranging from conventional compression molding to emerging additive manufacturing approaches are discussed in the context of morphological control and property optimization. Applications spanning aerospace structures, high-frequency electronics and protective coatings demonstrate the technological relevance of PBz composites. Critical challenges including network brittleness, high cure temperatures, and recyclability limitations are addressed alongside recent advances in dynamic covalent networks, vitrimer chemistry, and self-healing systems that promise to overcome these barriers. This review provides a comprehensive framework for understanding and engineering polybenzoxazine composites for next-generation advanced applications. Full article

The durability of concrete in chemically aggressive environments remains a major concern for marine structures, wastewater systems, industrial facilities, pavements, and foundations exposed to sulfate-bearing soils. Geopolymer concrete has attracted increasing attention as a lower-carbon alternative to ordinary Portland cement concrete because its aluminosilicate-rich reaction products, reduced portlandite content, and adjustable precursor–activator chemistry may enhance resistance to various chemical attack mechanisms. However, its durability is strongly governed by mixture composition and exposure regime, and therefore cannot be generalized across all geopolymer systems. This review provides a systematic and critical synthesis of the chemical attack resistance of geopolymer concrete, focusing on acid, sulfate, chloride, marine, wastewater, and combined aggressive exposures. The effects of precursor chemistry, calcium content, activator composition, curing regime, additives, fibers, aggregate type, recycled materials, and environmental coupling are examined in relation to degradation mechanisms and durability indicators. A PRISMA-informed methodology was used to identify, screen, verify, and synthesize primary experimental and modeling studies. The reviewed evidence indicates that low-calcium and well-polymerized geopolymer systems often exhibit favorable sulfate resistance due to the reduced availability of calcium-bearing phases that form expansive products, whereas chloride resistance is primarily governed by pore refinement, chloride transport, binding capacity, pore–solution alkalinity, and reinforcement corrosion behavior. In contrast, acid resistance remains more variable, depending on acid type, pH, exposure duration, solution renewal, calcium content, and the stability of protective silica-rich layers. Additives and alternative aggregates can enhance durability by refining the pore structure, improving the interfacial transition zone, or controlling cracking, but excessive or incompatible dosages may have adverse effects. Overall, geopolymer concrete offers strong potential for chemically aggressive infrastructure when designed through performance-based criteria and validated under realistic multi-exposure conditions. Full article

Lattice structures are widely utilized in lightweight engineering due to their design flexibility and tailorable mechanical properties. However, polymer lattices often exhibit limited load-bearing capacity and moderate crashworthiness under compression. This study proposes a hybrid reinforcement strategy based on the integration of carbon fiber-reinforced polymer (CFRP) rods into polymeric Kelvin-cell lattices. The specimens were manufactured via masked stereolithography, and the effects of rod placement pattern, the number of rods, and rod-length configuration were systematically investigated under quasi-static compression. Crashworthiness was evaluated in terms of force–displacement response, deformation mode, and crashworthiness metrics. Compared with the empty Kelvin-cell lattice, the best-performing hybrid configuration increased energy absorption, specific energy absorption, and mean crushing force by approximately 356%, 307%, and 356%, respectively. Mechanistically, distributed rod placement promoted more uniform load sharing, while the effect of increasing rod number depended strongly on the rod-length configuration. In addition, delayed or sequential reinforcement strategies provided superior performance and an enhanced balance between energy absorption and force efficiency. Regression models and ANOVA consistently identified rod-length configuration as the dominant design variable. These findings demonstrate that CFRP rod reinforcement can effectively enhance the crashworthiness of polymeric Kelvin-cell lattices, provided that the rod placement pattern, rod number, and rod-length configuration are designed jointly. Full article

Hybrid conductive materials have attracted increasing attention due to their combined electrical conductivity, mechanical flexibility, and sustainability. In this work, new hybrid materials based on polyaniline (PANI)-wrapped multi-walled carbon nanotubes (MWCNTs) and microfibrous cellulosic substrates were developed and assessed for photocatalytic degradation of a model dye pollutant. First, in situ oxidative polymerization of aniline in formic acid (FA) was conducted in the presence of MWCNTs to afford stable dispersions of carboxylated polyaniline-wrapped carbon nanotubes (c-PANI/MWCNTs). Next, the dispersions were used for affordable impregnation of microfibrous cellulosic filter paper. The influence of the initiator type—potassium peroxodisulfate (KPS) and hydrogen peroxide—on polymer–nanotube interactions, stabilization and surface deposition was emphasized. The structural, surface, morphological and thermal properties of the obtained dispersions and cellulose nanocomposites were systematically investigated using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and thermal gravimetric analysis. The results revealed strong interfacial interactions between c-PANI and the pristine MWCNTs, resulting in improved dispersion stability and effective and even surface deposition of the conductive c-PANI/MWCNT hybrids into the cellulose fiber mesh. The photocatalytic degradation of 5 ppm methylene blue (MB) dye in the presence of the developed nanocomposite materials under UV-A illumination was studied. The results showed that the c-PANI@MWCNT-impregnated cellulose substrates exhibited enhanced photocatalytic ability (up to 83% degree of degradation of MB dye) in comparison with the pure c-PANI. Full article

This perspective focuses on the field of solid waste recovery and resource utilization for end-of-life (EoL) wind turbine blades. Wind energy plays a central role in the global transition toward low-carbon energy systems owing to its technological maturity, scalability, and widespread resource availability. As global installed wind power capacity exceeded 1000 GW in 2024, improving the life-cycle energy efficiency and resource productivity of wind energy systems has become increasingly important. In this context, wind turbine blades (WTBs), the most material-intensive components with high embodied energy, are approaching large-scale end-of-life replacement, with global EoL blade waste projected to reach 2–4 million tons by 2030. Although blades may reach the end of their structural service life, they contain substantial quantities of reinforcing fibers and polymeric matrices that embody significant material and manufacturing energy. Integrating blade recycling into the wind energy value chain represents a critical opportunity to reduce dependence on energy-intensive virgin materials and lower life-cycle energy consumption and associated carbon emissions. However, the realization of energy-efficient circular utilization remains constrained by several challenges, including inefficient heat and mass transfer during blade depolymerization, limited valorization of resin-derived products, and performance degradation of recovered fibers. This perspective examines the material characteristics of blades from a life-cycle energy utilization standpoint, assesses existing recycling pathways, and identifies key technological and system-level bottlenecks. Emphasis is placed on process intensification, product upgrading, and design-for-circularity strategies to support the long-term sustainability of wind power systems. Full article

Development of sustainability systems for assessment of environmental impacts remains a paramount challenge for green and circular manufacturing of polymers. In this study, a comprehensive life cycle assessment (LCA) framework is developed for European polymeric waste by integrating OpenLCA, Ecoinvent v3.11, and Python-based machine learning (ML) algorithms. Cradle-to-gate, service-life, and cradle-to-grave assessments are performed for representative thermoplastic composite systems, including PP–PET–cotton, HDPE–glass fiber, and PEEK–carbon fiber composites, covering domestic, engineering, and high-performance polymer categories. The results demonstrate that raw material extraction and manufacturing stages dominate environmental impacts, contributing the highest shares to climate change, ecotoxicity, and non-renewable energy consumption. PP-based composite systems exhibit the lowest overall environmental burdens due to lower processing energy and simpler molecular structures, while HDPE-based systems show moderate impacts. PEEK-based composites present the highest impacts per unit mass, driven by energy-intensive synthesis and high processing temperature. Environmental impacts are evaluated using EF v3.1 and ReCiPe methodologies, supported by Monte Carlo simulations and ML-assisted uncertainty quantification. Monte Carlo simulations and ML-assisted LCA provide probabilistic ranges, uncertainty quantification, and predictive insights into impact indicators, enabling the development of a quantitative sustainability system based on probability–impact relationships. A Europe-wide assessment of 57 Mt of polymeric waste highlights that environmental burdens are concentrated in countries with high polymer production and consumption, emphasizing the importance of energy mix, recycling efficiency, and waste management strategies. Overall, this work demonstrates that digitalized LCA coupled with ML offers a powerful decision-support framework for sustainable polymer design, recycling optimization, and circular economy policy development, supporting the transition toward low-carbon and resource-efficient polymer systems in Europe. Full article

The recycling of carbon fiber-reinforced polymers (CFRPs), particularly carbon fiber-reinforced epoxy polymers (CFREPs), is a challenging problem because of their broad application spectrum, the amount of laminates produced per year, and the cost per kg of the carbon fiber fabric. Recently, several papers were published on the recycling of CFREPs through solvothermal methods that allow the recovery of the carbon fiber fabrics with a relatively low environmental impact. In the present paper, for the first time, the effect of the presence of flame retardants is discussed. A carbon fiber-reinforced epoxy polymer (CFREP) charged with P-, Zn-, B- and Al-based flame retardants, supplied by the aerospace industry, was subjected to a double-step solvothermal treatment. The epoxy matrix was successfully dissolved in monoethanolammine after a preswelling step in acetic acid. The experimental results show that the proposed process allows the full recovery of the carbon fabric with its original sizing layer without injury to the fiber. As confirmation, CFREP laminates produced with the recycled carbon fiber fabrics exhibited mechanical properties close to that of laminates obtained from the virgin epoxy/carbon prepreg. Contrary to what is reported in the literature, the present paper also shows that, in the studied case, whilst acetic acid treatment promotes swelling, it also causes the formation of a degraded surface layer that would impede complete removal of the polymeric matrix and full recovery of the carbon fabric if only acetic acid was used. On the basis of the known mechanism of flame retardancy of phosphates and borates, the degraded layer formation is attributed to the acidic character of the acetic acid. It is worth pointing out that the paper suggests, therefore, that the presence of flame retardants may strongly affect the solvothermal processes. Full article

The rapid growth of synthetic textile production has intensified the release of micro- and nanoplastics (MPs/NPs) into aquatic environments, primarily through industrial effluents and domestic laundering. Textile-derived microplastics, especially polyester fibers and polymeric coating fragments, constitute a significant fraction of plastic contamination in wastewater systems. Although wastewater treatment plants (WWTPs) can remove a large proportion of MPs, substantial quantities accumulate in sewage sludge, raising concerns about long-term environmental persistence and secondary release pathways. This review critically examines the sources, classification, and release mechanisms of textile-based micro- and nanoplastics, including fibrous debris and coating-derived fragments. Then it focuses on current identification and removal technologies, such as sedimentation, coagulation/flocculation, electrocoagulation, flotation, membrane filtration, adsorption, and biodegradation, and on the emerging strategy of converting recovered microplastics into value-added porous carbon materials via hydrothermal treatment and pyrolysis. Carbonized microplastics exhibit high surface area and adsorption capacity for dyes, heavy metals, and organic pollutants, offering a circular approach that simultaneously mitigates plastic pollution and enhances wastewater treatment efficiency. By integrating source control, optimized removal technologies, and carbonization-based valorization, this review proposes a dual-benefit framework that transforms textile-derived microplastic waste from an environmental liability into a functional resource for sustainable water purification. Full article

The sustainable conversion of agricultural waste biomass, particularly crop residues such as corn stover, into high-value products is vital for reducing their open-field burning and mitigating environmental hazards. The hydrothermal carbonization (HTC) process integrated with natural deep eutectic solvents (NADES) presents an alternative approach for valorizing biomass into lignin-rich solid fuels and fermentable sugars for bioethanol production. In this study, corn stover was subjected to HTC using deionized (DI) water, a xylose-based NADES (ChCl:Xy:W), and an oxalic acid-based NADES (ChCl:OA:W) in a 150–300 °C temperature range to optimize both solid fuel and sugar stream yields. Characterization, including fiber analysis, SEM, FTIR, EDS, and bomb calorimetry, was conducted to evaluate structural, compositional, and energetic transformations. The results explored the HTC process, restructuring the biomass, promoting extensive hemicellulose solubilization and cellulose depolymerization, as well as substantially enriching lignin and polymerized compounds with increasing temperature. In addition, the DI water at 300 °C generated a lignin-rich residue, the Xy-based NADES effectively removed ash and extractives, and the OA-based NADES produced the most carbon-dense hydrochar with the highest calorific value. Collectively, these findings demonstrate that solvent-assisted HTC may be employed as a possible strategy for the valorization of agricultural residues into high-energy solid fuels. Full article

Fused Deposition Modeling (FDM) is a widely used additive manufacturing technique that enables the fabrication of components using polymeric and composite materials; however, the mechanical performance of printed parts is jointly influenced by multiple printing parameters, which complicates the control and prediction of their mechanical properties. In this study, an attention-enhanced multi-modal convolutional neural network (ATT-MM-CNN) is developed to predict the tensile performance of carbon fiber reinforced polylactic acid (PLA-CF) composites manufactured by FDM. Four key printing parameters, layer thickness, nozzle temperature, material flow rate, and printing speed, are systematically investigated, resulting in 256 parameter combinations and corresponding tensile test data for constructing a multi-modal dataset. By integrating multi-modal feature representations and incorporating an attention mechanism, the proposed model effectively learns the nonlinear relationships between printing parameters and mechanical performance under multi-parameter conditions. The results show that all evaluation metrics, including accuracy, precision, recall, and F1-score, exceed 0.95, and the prediction accuracy is improved by at least 17.3% compared with baseline models. These findings demonstrate that the proposed ATT-MM-CNN provides an effective and reliable framework for tensile property prediction and process-parameter optimization of FDM-printed composite structures. Full article

Conventional particleboards often exhibit limited mechanical strength, which restricts their use in load-bearing and high-performance applications; reinforcing these boards with carbon fibers offers a potential solution to overcome these limitations. This study investigated the effect of carbon fiber (CF) content on the mechanical performance of single-layer particleboards bonded with polymeric methylene diphenyl diisocyanate (pMDI) adhesive. Carbon fibers were examined as a reinforcement to improve the mechanical properties of particleboards. Experimental boards were produced with 0, 10, 20, 30, 40, and 50% CF (based on the oven-dry mass of wood particles). The analysis included density profile distribution, modulus of rupture (MOR), modulus of elasticity (MOE), and screw withdrawal resistance (SWR). The results showed that mechanical performance improved only at lower CF contents. The most pronounced effect was observed at 10% CF, where MOR increased from 15.2 MPa (control) to 19.2 MPa, and MOE increased from 2.45 GPa to 2.91 GPa. Higher CF additions (≥20%) did not yield further improvements, and at elevated levels (≥30%), bending performance decreased (MOR dropped to 14.1–13.5 MPa) due to poor fiber dispersion and weakened interfacial bonding between fibers and wood particles. Screw withdrawal resistance increased gradually with CF content, from 156 N in the control boards to 182 N at 50% CF, although the improvement was limited by adhesion quality and mat heterogeneity. Overall, the study demonstrates that small CF additions can enhance selected mechanical properties of particleboards, whereas higher loadings negatively affect performance due to microstructural incompatibilities. Full article

This study presents a new ternary copolymer synthesized via aqueous free-radical polymerization from sodium humate, sodium 2-methylprop-2-ene-1-sulfonate (SMAS), and 2-acrylamido-2-methylpropane sulfonic acid (AMPS). The resulting highly water-soluble, three-dimensional porous copolymer is complexed with aluminum sulfate to form a composite admixture containing AlO(OH), which acts as a highly effective accelerator for cement hydration. This system significantly shortens the initial and final setting times to averages of 2.62 min and 4.53 min, respectively, and enhances early-age mechanical strength (1.7 MPa compressive, 1.4 MPa flexural at 6 h). These improvements are correlated with the formation of key crystalline phases, including Al₂Si₂O₅(OH)₄ and Ca₃Al₂O₆·xH₂O gel. Incorporation of 50-mesh carbon fibers further reduces setting times (2.21 min initial, 3.93 min final) and increases 24 h strength (5.2 MPa compressive, 2.7 MPa flexural), despite a slight reduction in early strength (at 6 h). In contrast, 200-mesh carbon fibers extend the initial setting time and diminish early strength, associated with the formation of less effective gel phases such as Ca₃Al₂O₆·xH₂O, (CaO)_x(Al₂O₃)₁₁, and Ca₄Al₂O₇·xH₂O. Among these, the Al₂Si₂O₅(OH)₄ phase demonstrates superior performance, while finer carbon fibers show limited effectiveness in bridging hydration products. Conventionally employed as retarders or reinforcing agents, humate-based polymers and carbon fibers are shown here to function as dual-functional admixtures—serving as efficient setting accelerators while enhancing mechanical properties through tailored material design. This strategy offers a promising pathway for developing advanced multifunctional cement admixtures. Full article