Search Results (1,653)

The aviation industry requires a series of actions that will transform its current status, aiming for sustainable operations. Aviation’s end-of-life stream is a pivotal lever for circularity, yet current dismantling and recycling practices leave significant value unrealized. Circular Economy could be considered as a transformational approach to the aviation industry and address its environmental and economic challenges, meeting sustainability principles. This study conducts a PRISMA-guided qualitative systematic review across academic and industry sources to synthesize regulations, technologies, and economics of aircraft decommissioning. It aims to quantify material recovery potential and environmental gains at the aircraft level and assess technology readiness and cost drivers for metals, polymers, and composites. Findings indicate that optimized decommissioning enables high-value part reuse and substantial material recovery (notably aluminum), with associated lifecycle greenhouse-gas avoidance at the aircraft scale. However, high costs, weak regulations, and limited recycling technologies hinder adoption. Results show that optimized dismantling and certified part-reuse pathways can recover up to 85–90% of total aircraft mass, with potential CO₂-emission avoidance of 25–35 t per narrow-body aircraft compared with landfill disposal. Metal recycling technologies (TRL 8–9) already achieve high yields, whereas polymer and composite recycling remain limited (TRL 5–6) by purity and certification barriers. A comparative assessment of EU, US, and Asia–Pacific regulations identifies enforcement and infrastructure gaps hindering implementation. The study introduces an integrated CE roadmap for aviation comprising (i) standards-aligned design-for-disassembly and digital traceability, (ii) accredited MRO-to-reuse networks, and (iii) performance-based policy incentives. Full article

Graphene-based materials have been the subject of extensive scientific investigations owing to their distinctive properties and versatile functionalities. However, their applications are hindered due to limited material performance, difficulties in recycling, and high costs during manufacturing. Considering this, studies have developed graphene or its derivatives by combining it with other components, while some of these composites revealed significantly improved performance with lesser consumption of raw materials; the underlying mechanisms remain inadequately elucidated. Therefore, the aspiration for novel applications of graphene-based materials could be significantly improved with the full utilization of the synergistic effects of these materials. In this review, we intend to discuss the synergistic activities and their inherent mechanisms between graphene or its derivatives and metals, metal oxides, polymers, and bioactive compounds, among others. The effectiveness of synergisms in enhancing the performance of graphene-based composites is corroborated by studies in a variety of application areas such as antimicrobial materials, cancer therapy, sensors, electronic devices, catalysts, and more. The content presented will be useful to guide the future development of graphene-based materials that are highly efficient and environmentally friendly. Full article

End-of-life tires (ELTs) are an important source of energy and materials, with ELT powder (ELTp) being a secondary raw material of increasing industrial interest. However, the complex structure and composition of ELTp rubber pose technological difficulties and scientific challenges in some high-performance applications in the rubber industry. The mechanical recycling of ELTp produces ground tire rubber (GTR) powder, which is used, among other applications in the rubber field, to prepare thermoplastic vulcanizates (TPVs) due to the interest in these materials in the automotive and construction sectors. Over the last few decades, different approaches have been explored to minimize the limitations of these TPVs, including their large particle size and poor compatibility with GTR powder in other polymer matrices. This study applies different recycling procedures to GTR powder, based on thermal, chemical and mechanical methods, and combinations thereof, to minimize interfacial issues with other matrices used in TPV preparation. The effect of the different rubber recycling processes on the performance of the resulting TPVs was evaluated, optimizing the fraction of recycled rubber from ELTp and the vulcanization system to enhance the mechanical properties and obtain industrially competitive products. Full article

Large-format additive manufacturing (LFAM) is an enabling manufacturing technology capable of producing large parts with highly complex geometries for a wide variety of applications, including automotive, infrastructure/construction, and aerospace mold and tooling. In the past decade, the LFAM industry has seen widespread use of bio-based, glass, and/or carbon fiber reinforced thermoplastic composites which, when printed, serve as a lower-cost alternative to metallic parts. One of the highest-volume materials utilized by the industry is carbon fiber (CF)-filled polycarbonate (PC), which in out-of-autoclave applications can achieve comparable mechanical performance to metal at a significantly lower cost. Previous work has shown that if this material is recovered at various points throughout the manufacturing process for both the lab and pilot scale, it can be mechanically recycled with minimal impacts on the functional performance and printability of the material while significantly reducing the feedstock costs. End-of-life (EOL) CF-PC components were processed through industrial shredding, melt compounding, and LFAM equipment, followed by evaluation of the second-life material properties. Experimental assessments included quantitative analysis of fiber length attrition, polymer molecular weight degradation using gel permeation chromatography (GPC), density changes via pycnometry, thermal performance using dynamic mechanical analysis (DMA), and mechanical performance (tensile properties) in both the X- and Z-directions. Results demonstrated a 24.6% reduction in average fiber length compared to virgin prints, accompanied by a 21% decrease in X-direction tensile strength and a 39% reduction in tensile modulus. Despite these reductions, Z-direction tensile modulus improved by 4%, density increased by 6.8%, and heat deflection temperature (HDT) under high stress retained over 97% of its original value. These findings underscore the potential for integrating mechanically recycled CF-PC into industrial LFAM applications while highlighting the need for technological innovations to mitigate fiber degradation and enhance material performance for broader adoption. This critical step toward circular material practices in LFAM offers a pathway to reducing feedstock costs and environmental impact while maintaining functional performance in industrial applications. Full article

This study explores the mechanical behavior of concrete reinforced with recycled carbon fiber (RCF) and incorporating modified basic oxygen furnace slag (MBOF) as a sustainable aggregate. The RCF was recovered from waste carbon fiber-reinforced polymer (CFRP) bicycle rims via microwave-assisted pyrolysis (MAP), while MBOF was produced by water-based treatment of hot BOF slag. The experimental program included compressive, splitting tensile, and flexural strength tests, as well as impact resistance and stress-reversal Split Hopkinson Pressure Bar (SRSHPB) tests. The effects of RCF length (6 mm and 12 mm) on the mechanical performance of MBOF-based concrete were systematically examined. The results demonstrated that incorporating MBOF as aggregate, combined with the addition of RCF, significantly enhanced both static strength and dynamic impact resistance. Compared with fiber-free MBOF concrete, the incorporation of 6 mm and 12 mm RCF increased compressive strength by 3.03% and 13.77%, flexural strength by 14.50% and 19.74%, and splitting tensile strength by 2.60% and 25.84%, respectively. Similarly, the impact number increased by approximately 6.81 and 12.67 times for the 6 mm and 12 mm RCF specimens, respectively, relative to the fiber-free specimen. Furthermore, the SRSHPB test results indicated that MBOF concrete reinforced with 12 mm RCF exhibited greater dynamic compressive strength than that reinforced with 6 mm RCF. Overall, MBOF concrete incorporating 12 mm RCF demonstrated superior performance to its 6 mm counterpart across all evaluated strength parameters. These findings highlight the potential of utilizing metallurgical and composite waste to develop high-performance, sustainable concrete materials. Full article

This paper presents the investigation of the effect of electron radiation or the combined action of this radiation and triallyl isocyanurate (TAIC) on the structural, thermal, and mechanical properties of epoxy resin filled with a fraction of dust fibers (DFs) from recycled wind turbine blades. The resin containing 20 wt% of DF was irradiated with doses of 40, 80, 120, and 160 kGy. The results showed that electron radiation had only a slight effect on the properties of the studied composite, mainly on its glass transition temperature. More significant changes were observed with the combined action of radiation and TAIC. The main effect that occurred after the TAIC addition was the plasticization of the polymer matrix. With its participation, the glass transition temperature, thermal stability, and the hardness of the material and its flexural modulus were significantly reduced. The degree of change in these properties was regulated by the radiation dose. Furthermore, no significant changes in the composite structure were observed after radiation treatment, while the introduction of TAIC into the polymer matrix caused the formation of gas cells, probably due to the partial decomposition of TAIC. Full article

The basis of the construction industry is building materials with high-quality indicators in terms of physical, mechanical, and thermophysical characteristics, however, there are a number of issues affecting the quality of manufactured products. The development of the construction industry provides new opportunities for designing efficient construction facilities. To obtain enhanced design capabilities, it is very important to relieve the load on the structure, and this can be achieved by reducing the mass of materials without losing strength. This study investigates the enhancement of foam concrete through the combined incorporation of mineral fibers recycled from basalt insulation waste and complex polymer modifiers. The aim was to improve the material’s mechanical performance, durability, and pore structure stability while promoting sustainable use of industrial by-products. The experimental program included tests on density, compressive strength, water absorption, and thermal conductivity for mixtures of different densities (400–1100 kg/m³). Results demonstrated that the inclusion of mineral fibers and polymer modifiers significantly enhanced structural uniformity and pore wall integrity. Compressive strength increased by up to 35%, water absorption decreased by 25%, and thermal conductivity was reduced by 18% compared with the control mixture. Full article

This work investigates the effect of a bio-based plasticizer derived from used sunflower oil on the crystallization behavior of poly (lactic acid) (PLA), comparing it with that of the conventional plasticizer tributyrin. This study aims to explore biodegradable alternatives to petroleum-based materials and to evaluate their potential in modulating PLA crystallization kinetics without altering the crystalline structure of the resulting sustainable material solutions with tailored performance. PLA-based films containing 5%, 10%, and 15% plasticizer were prepared and characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X-Ray diffraction (XRD). DSC analysis showed a decrease in the glass transition temperatures upon plasticization, with tributyrin producing a more pronounced effect than the recycled sunflower oil plasticizer. XRD patterns confirmed that the crystalline form of PLA remained unchanged regardless of plasticizer type or content. POM revealed that both plasticizers influenced crystallization kinetics, with the bio-plasticizer promoting larger and more sparsely distributed spherulites than tributyrin, indicating differences in nucleation efficiency and crystal growth. Crystallization kinetics were further analyzed using the Avrami model, the Lauritzen-Hoffman theory, and the isoconversional method. Avrami analysis indicated that nucleation mechanisms were largely unaffected, although the overall crystallization rate increased upon plasticization. Lauritzen-Hoffman analysis confirmed crystallization in Regime III, controlled by nucleation, while isoconversional analysis showed reduced activation energy in plasticized PLA. These findings highlight the ability of bio-derived plasticizers to modulate PLA crystallization, promoting the valorization of a food industry residue as a sustainable plasticizer. This study hopes to contribute relevant knowledge to emerging areas of polymer processing, such as 3D printing, to develop sustainable and high-performance PLA-based materials. Full article

The oil and gas industry generates substantial amounts of polymeric waste each year, including sucker rod guides manufactured from premium thermoplastics such as Polyphenylene Sulphide (PPS), Polyacrylamide (PAA), Polyamide (PA), and Polyether ether ketone (PEEK). It is estimated that, annually, approximately 18,600 metric tonnes of polymeric sucker rod guides are discarded worldwide, contributing significantly to landfill accumulation. This paper critically reviews the behaviour of polymeric rod guides when exposed to downhole environments where high temperature, pressure, contamination, and severe mechanical stresses act simultaneously. These components are essential in maintaining system reliability, yet research and development on polymeric rod guides remain limited, and investigations into their degradation and failure mechanisms are non-existent. In addition, there are currently no established approaches for recycling or reusing worn polymeric guides, which restricts progress toward sustainability and contributes to the increased accumulation of polymer waste in landfills. This review highlights these gaps and discusses future research directions that could improve the performance and service life of glass-fibre-reinforced polymeric components, while also creating opportunities for recycling and circular economy. Full article

Thermoplastic composites are growing in popularity in the aerospace and automotive industries; they enable weldable and recyclable structures. Resistance welded hybrid thermoplastic and metal joints are attractive for rapid assembly, but the thermal mismatch between metals and polymers introduces residual stresses, which can drive edge debonding and compromise durability. This study presents fabricated single-lap PC/CF–Al7075 coupons with measured mid-span bow resulting from welding, evaluated bond quality by step-heating thermography, and an evaluated framework for residual stress prediction using Ansys complemented by a bimetal analytical check. Three thermal cycles were examined with different temperature gradients (200, 220, 240 °C): the measured bow was 16.5 mm and remained constant, whereas analytical calculation increased with ΔT similarly to the FEM prediction. The current FEM under predicted the bow (Mean Absolute Percentage Error is 21%), showing stress contours that decay with distance from the bond and revealing pronounced peaks in both σ_xx and σ_zz components at weld edges, consistent with shear-lag theory. FEM returned edge-peaked peel rising from 43 to −64 MPa and σ_xx was up to 12% more compressive than analytical calculation; an effective CF/PC CTE of 1.5 × 10⁻⁶ K⁻¹ reconciled curvature with test better than catalogue values. The temperature insensitive bow is attributed to polycarbonate flow/viscoelastic relaxation above Tg and hot relaxation in aluminum, with effects not represented in the elastic models. Edge peel and shear govern initiation risk. Full article

Analysis of the impact of aging processes induced by environmental conditions, particularly aggressive ones, on the properties of polymeric materials and products made from them has been the subject of intensive research for many years. Developing materials characterized by high resistance to the specific external factors in which these materials are used is a key issue in the context of developing a sustainable economy aimed at minimizing waste and extending the service life of polymeric components. The main objective of this research was to assess and quantify the degradation mechanisms of polymeric materials manufactured using additive Fused Deposition Modeling (FDM) technology when exposed to aggressive marine environments. To achieve this, the study analyzed the influence of seawater corrosion conditions on the changes in mechanical and rheological properties of two polymeric materials: recycled polylactide (rPLA) and a wood–polymer composite (WPC) based on PLA reinforced with wood flour (MD). The results revealed that rPLA exhibited an approximately 16% decrease in average molecular weight after 9 months of seawater exposure, accompanied by a 37% reduction in tensile strength and a 24% decrease in elastic modulus. In the case of the WPC, the molecular weight decreased by about 20%, while tensile strength and elastic modulus dropped by 30% and 51%, respectively. The findings provide quantitative evidence of the susceptibility of additively manufactured biodegradable polymers to marine-induced degradation, highlighting the necessity of further optimization for maritime and coastal applications. Full article

Rubberized concrete is a novel green building material that enhances many features when rubber particles are incorporated into cement mortar, simultaneously yielding economic benefits through the recycling of waste tires. This study applies styrene–butadiene latex (SBL) for toughening treatment. The investigation delves into the mechanism by which SBL improves the interface between rubber and cement, encompassing macroscopic mechanical properties, microscopic structural characteristics, and nano-scale interfacial interactions. Macroscopic mechanical tests reveal a significant increase in flexural strength, shear strength, and compressive strength of the composite concrete upon the introduction of SBL and rubber. Specifically, the compressive strength improved by 8.8%, shear strength by 13.7%, and flexural strength by 18.9% at 28 days. Through electron microscopy observation of corresponding polymer cement concrete sections, observations reveal that SBL reinforces both interfaces and elucidates its bonding impact at the micro-level interface. Molecular dynamics (MD) modeling of SBL/rubber/CSH is employed at the nanoscale to compute and examine the local structure, dynamic behavior, and binding energy of the interface. The findings indicate that SBL mitigates interface impacts, enhances interface hydrogen bonds, van der Waals interactions, $\mathrm{C}\mathrm{a}-\mathrm{H}$ coordination bonds, and stability, consequently improving interfacial adhesion and fortifying the feeble interface bonding between organic polymers (rubber) and inorganic silicates (CSH). Full article

The traditional chemical vapor deposition (CVD)graphene transfer process generates a large amount of solvent waste, posing a significant sustainability challenge. To address this, we designed a Cyclic Cleaning Multi-Chamber (CCMC) system. Inspired by Soxhlet extraction, the CCMC enables closed-loop solvent recycling through integrated distillation, condensation, and reflux mechanisms. Experimental results show that the system effectively removes poly(methyl methacrylate) (PMMA) residues from transferred graphene without damaging its structural integrity, a finding confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The CCMC system achieves a solvent recovery efficiency of over 98% across 25 cycles using acetone, significantly reducing solvent consumption compared to conventional methods. While providing this substantial environmental benefit, the energy demand remains moderate, increasing by only about 15 kWh. These results position the CCMC as a scalable, eco-friendly solution for the semiconductor and nanomaterial industries, promoting the broader adoption of sustainable manufacturing practices. Full article

The growing demand for sustainable solutions in the plastics industry has highlighted the need to reintroduce post-industrial polymer waste into high-performance applications. This study focuses on the mechanical recycling of automotive scraps containing variable proportions of polycarbonate (PC), acrylonitrile–butadiene–styrene (ABS), and a commercial PC/ABS blend. After determining the composition of two representative batches, a screening of seven commercial compatibilizers and impact modifiers was performed to improve impact strength. Among them, an ethylene–methyl acrylate–glycidyl methacrylate (E-MA-GMA) terpolymer was identified as the most effective additive. Its influence was further investigated through a mixture design approach, varying the composition of the three polymer phases and the additive content (0–10 wt.%). The resulting response surface model revealed a significant increase in impact resistance in PC-rich formulations with increasing E-MA-GMA content, while ABS and PC/ABS showed more complex trends. Rheological, mechanical, and thermal analyses supported the observed behavior, suggesting improved matrix compatibility and reduced degradation during processing. The proposed model enables the prediction of impact performance across a wide range of compositions, offering a practical tool for the optimization of recycled blends. These findings support the potential of targeted compatibilization strategies for closed-loop recycling in the automotive sector. Full article

Plastic recycling has been a challenge worldwide due to various reasons, including limited profit margins, the demand for high-quality plastic reprocessing techniques to make products comparable to those from virgin materials, and challenges in sorting and processing. This problem became particularly urgent in the small towns in the U.S., where plastic waste was shipped overseas for treatment, but now it is not accepted in some countries. This study aims to understand the plastic value chain and find the necessary factors for a circular economy model of both environmental and economic settings. In this study, an educational plastics reprocessing workspace was developed with manufacturing processes such as shredding, filament extruding, 3D printing, and injection molding. A series of products was developed to increase the value of the recycled polymers. In addition, quality control of recycled polymers such as polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET), and polyethylene terephthalate glycol (PETG) was examined. By collaborating with a university manufacturing lab, this work illustrates how plastics can be collected, prepared, and reprocessed, serving as a platform for student learning and community outreach. This study contributes to the body of knowledge by presenting a case-based educational model for community-level plastic recycling and reprocessing in a college town context. Full article