Search Results (163)

This study presents a cost-effective, carbon-negative construction material for affordable housing, developed entirely from locally available agricultural wastes: rice husk ash, wood ash, and rice straw—materials often problematic to dispose of in many African regions. Rice husk ash provides high amorphous silica, acting as a strong pozzolanic agent. Wood ash contributes calcium oxide and alkalis to serve as a reactive binder, while rice straw functions as a lightweight organic filler, enhancing thermal insulation and indoor climate comfort. These materials undergo natural pozzolanic reactions with water, eliminating the need for Portland cement—a major global source of anthropogenic CO₂ emissions (~900 kg CO₂/ton cement). This process is inherently carbon-negative, not only avoiding emissions from cement production but also capturing atmospheric CO₂ during lime carbonation in the hardening phase. Field trials in Kenya confirmed the composite’s sufficient structural strength for low-cost housing, with added benefits including termite resistance and suitability for unskilled laborers. In a collaboration between the University of Tartu and Kenyatta University, a semi-automatic mixing and casting system was developed, enabling fast, low-labor construction of full-scale houses. This innovation aligns with Kenya’s Big Four development agenda and supports sustainable rural development, post-disaster reconstruction, and climate mitigation through scalable, eco-friendly building solutions. Full article

This review article focuses on the long-term durability challenges associated with bamboo fiber-reinforced polymer composites when subjected to various environmental aging conditions such as water immersion, hygrothermal fluctuations, ultraviolet (UV) radiation, soil burial, and refrigerated storage. The primary issue addressed is the degradation of mechanical and structural performance of bamboo fiber-reinforced polymer composites due to moisture absorption, fiber swelling, and fiber–matrix interface deterioration. To mitigate these aging effects, the study evaluates and compares multiple strategies, including chemical and physical fiber surface treatments, filler additions, and fiber hybridization, which aim to enhance moisture resistance and mechanical stability. These composites are relevant in automotive interiors, construction panels, building insulation, and consumer goods due to their eco-friendly nature and potential to replace conventional synthetic composites. This review is necessary to consolidate current knowledge, identify effective enhancement approaches, and guide the development of environmentally resilient bamboo fiber-reinforced polymer composites for real-world applications. Full article

In response to the rising demand for sustainable engineering materials and waste valorisation strategies, this study investigates the multi-objective optimisation of eco-friendly hybrid composites reinforced with natural fibres and industrial waste. Sixteen composite specimens were fabricated using compression moulding by varying sisal fibre from 0 to 45 wt.%, banana fibre from 0 to 45 wt.%, NaOH alkali treatment from 0 to 6%, and red mud filler from 1 to 4 wt.%. Mechanical properties were evaluated following ASTM standards D256 for impact strength, D790 for flexural strength, D638 for tensile strength, D5379 for shear strength, and E18 for hardness. The Taguchi method combined with grey relational analysis was employed to identify optimal processing conditions. The best mechanical performance, with an impact strength of 6.57 J, flexural strength of 72.58 MPa, and tensile strength of 65.52 MPa, was achieved with 30 to 45 wt.% sisal fibre, 15 wt.% banana fibre, 6% NaOH, and 3 to 4 wt.% red mud. ANOVA revealed that NaOH treatment had the most significant influence on mechanical properties, with high F values and p values close to 0.05. Grey relational analysis proved more effective for multi-objective optimisation, with the highest grey grade of 0.894 observed in the specimen containing 45 wt.% sisal fibre, 6% NaOH, and 2 wt.% red mud. These findings highlight the critical role of fibre treatment and hybrid reinforcement in enhancing performance. The optimised composites demonstrate strong potential for use in automotive interior panel applications, offering a sustainable alternative with balanced strength and reduced environmental impact. Full article

This study developed sustainable biocomposites composed of polylactic acid (PLA) and surface-treated pineapple core powder (PACP), fabricated via extrusion and fused deposition modelling (FDM). PACP loadings of 1–3 vol% were combined after chemical modification with NaOH and silane to improve interfacial bonding. Particle morphology showed increased porosity and surface roughness following treatment. The melt flow index (MFI) increased from 31.56 to 35.59 g/10 min at 2 vol% PACP, showing improved flowability. Differential scanning calorimetry (DSC) showed the emergence of cold crystallization (T_cc ~121 °C) and an increase in crystallinity from 35.7% (neat PLA) to 47.3% (2 vol% PACP). Thermogravimetric analysis showed only slight decreases in T₅ and T_max, showing the thermal stability. The mechanical testing of extruded filaments showed increased modulus (1463 to 1518 MPa) but a decrease in tensile strength and elongation. For the 3D-printed samples, elongation at break increased slightly at 1–2 vol% PACP, likely because of the improvement in interlayer fusion. Though, at 3 vol% PACP, the mechanical properties declined, consistent with filler agglomeration observed in SEM. Overall, 2 vol% PACP offered the optimal balance between printability, crystallinity, and mechanical performance. These results reveal the possibility of PACP as a value-added biowaste filler for eco-friendly PLA composites suitable for extrusion and 3D printing applications. Full article

This study explores the flame retardancy and structural behavior of silicone foam composites filled with halogen-free flame retardants, aiming to evaluate their feasibility for use in mass transportation applications. Silicone foam specimens incorporating magnesium hydroxide and expandable graphite were prepared and compared with unfilled silicone foam under both static and dynamic loading conditions. Uniaxial compression and simple shear tests were conducted to assess mechanical behavior, and a second-order Ogden model was employed to represent hyperelasticity in the finite element analysis. Fire performance was evaluated using cone calorimeter tests in accordance with ISO 5660-1. The results showed a 53.6% reduction in peak heat release rate (PHRR) and a 48.1% decrease in MARHE upon the addition of flame retardants, satisfying relevant fire safety standards. Although the addition of fillers increased the compressive stiffness and reduced rebound resilience, static comfort indices remained within acceptable ranges. These findings confirm that halogen-free filled silicone foams exhibit significantly enhanced fire retardancy while maintaining sufficient mechanical integrity and seating comfort, demonstrating their potential as eco-friendly alternatives to conventional polyurethane foams in large-scale transportation applications. Full article

This research assessed novel, eco-friendly intumescent coatings utilizing cork and recycled glass as sustainable alternatives to synthetic fire retardants, aiming to reduce environmental impact while maintaining robust fire performance. Coatings underwent up to 600 h of UV light exposure for durability assessment, followed by chemo-physical characterization. Fire exposure tests evaluated in-situ char formation and foaming. All functionalized coatings exhibited suitable intumescent behavior, forming protective char layers even after extensive UV aging. Microscopic analysis showed good additive integration, while FTIR spectroscopy revealed UV-induced chemical changes. Fire resistance tests confirmed the superior performance of functionalized coatings over the commercial reference. The AP-IC system demonstrated the best intumescence, achieving significantly lower maximum temperatures (e.g., 167.3 °C for AP-IC-600) and heating rates. Crucially, the sustainable RG-IC and CK-IC batches showed promising intumescent properties, even improving with UV exposure. Notably, the foamed cross-sectional area of the aged RG-IC samples doubled compared to their unaged counterparts, reaching a maximum temperature of 166.9 °C. These findings highlight the potential of eco-friendly hybrid coatings to enhance fire safety, particularly in critical sectors like naval engineering, aligning with circular economy principles and the growing demand for sustainable, high-performance materials. Full article

Flexible electronics is an applicative field in continuous expansion. This article addresses the requirements of this domain regarding eco-friendly and flexible components from a renewable chitosan polysaccharide that is progressively reinforced with barium titanate nanoparticles. Ultrafine ceramic powder was produced by the coprecipitation method, and the resulting phase composition and morphology were investigated by X-ray diffraction and transmission electron microscopy, together with the perovskite structure of the spherical nanoparticles. FTIR studies were conducted to elucidate the interactions between the two constituting phases of the composites. The filler dispersion in the matrix was checked by scanning electron microscopy. The rheological percolation threshold was compared with that extracted from electrical measurements. The thermal behavior was assessed by thermogravimetry and differential scanning calorimetry. The dielectric properties as a function of frequency and applied electric field were investigated, and the results are discussed in terms of extrinsic contributions. The current results demonstrate a straightforward method for producing tunable flexible structures. Full article

In this study, polyvinyl alcohol (PVA) films were reinforced with lignocellulosic nanofibers (LCNFs) extracted from bamboo shoot shells using a choline chloride-based deep eutectic solvent (DES). A filler loading of 10 wt% was identified as the optimal condition for enhancing film performance. To improve interfacial compatibility between the PVA matrix and LCNFs, three surface modification treatments were applied to the nanofibers: hydrochloric acid (HCl) hydrolysis, citric acid (CA) crosslinking, and a dual modification combining both methods (HCl&CA). Among all formulations, films incorporating dual-modified LCNF at 10 wt% loading exhibited the most significant improvements. Compared to neat PVA, these composites showed a 79.2% increase in tensile strength, a 15.1% increase in elongation at break, and a 33.1% enhancement in Young’s modulus. Additionally, thermal stability and barrier properties were improved, while water swelling and solubility were reduced. Specifically, the modified films achieved a thermal residue of 9.21% and the lowest degradation rate of 10.81%/min. Water vapor transmission rate and oxygen permeability decreased by 18.8% and 18.6%, respectively, and swelling and solubility dropped to 14.26% and 3.21%. These results highlight the synergistic effect of HCl hydrolysis and CA crosslinking in promoting uniform filler dispersion and strong interfacial adhesion, offering an effective approach to valorizing bamboo shoot shell waste into high-performance, eco-friendly packaging materials. Full article

The rapid advancement of sustainable materials has driven the need for high-performance polymer nanocomposites with superior mechanical, thermal, and structural properties. In this study, a novel RPET/PA-11/Joncryl^® nanocomposite reinforced with halloysite nanotubes (HNTs) is developed for the first time, marking a significant breakthrough in polymer engineering. Six different proportions of HNT (0, 1, 2, 3, 4, and 5 phr) are introduced to the blend of rPET/PA-11/Joncryl^® through a twin-screw extruder and injection moulding machine. The incorporation of HNTs into the RPET/PA-11 matrix, coupled with Joncryl^® as a compatibilizer, results in a synergistic enhancement of material properties through improved interfacial adhesion, load transfer efficiency, and nanoscale reinforcement. Comprehensive characterization reveals that the optimal formulation with 2 phr HNT (NCS-H2) achieves remarkable improvements in tensile strength (56.14 MPa), flexural strength (68.34 MPa), and Young’s modulus (895 MPa), far exceeding conventional polymer blends. Impact resistance reaches 243.46 J/m, demonstrating exceptional energy absorption and fracture toughness. Thermal analysis confirms enhanced stability, with an onset degradation temperature of 370 °C, attributing the improvement to effective matrix–filler interactions and restricted chain mobility. Morphological analysis through FESEM validates uniform HNT dispersion at optimal loading, eliminating agglomeration-induced stress concentrators and reinforcing the polymer network. The pioneering integration of HNT into RPET/PA-11/Joncryl^® nanocomposites not only bridges a critical gap in sustainable polymers but also establishes a new benchmark for polymer nanocomposites. This work presents an eco-friendly solution for engineering applications, offering mechanical robustness, thermal stability, and recyclability. The results form the basis for next-generation high-performance materials for industrial use in automotive, aerospace, and high-strength structural applications. Full article

The objective of this study was to explore the potential of creating advanced insulating biocomposites using waste almond and hazelnut shells as particulate fillers, combined with a geopolymer binder, to develop sustainable materials with minimal environmental impact. Optimal conditions for the preparation of biocomposites were determined by measuring the compressive strengths. The aforementioned optimal conditions included a geopolymer to waste nutshell mass ratio of 2, room-temperature curing, and the use of metakaolin geopolymers activated with potassium solutions. Notably, the highest compressive strengths of 4.1 MPa for hazelnut shells biocomposite and 6.4 MPa for almond shells biocomposite were obtained with milk of lime pretreatment at 80 °C for 1 h. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and Fourier transform infrared spectroscopy (FTIR) analyses revealed better adhesion, as well as improved geopolymer gel polymerization. Furthermore, thermal conductivity and diffusivity measurements demonstrated values characteristic of insulating materials, reinforcing their potential for eco-friendly construction applications. Full article

Cellulose nanofibril (CNF) is a sort of novel nanomaterial directly extracted from plant resources, inheriting the advantages of cellulose as a cheap, green and renewable material for the development of new-generation eco-friendly electronics. In recent years, CNF-based triboelectric nanogenerator (TENG) has attracted increasing research interests, as the unique chemical, morphological, and electrical properties of CNF render the device with considerable flexibility, mechanical strength, and triboelectric output. In this study, we explore the use of isoreticular metal-organic frameworks (IRMOF) as functional filler to improve the performance of CNF based TENGs. Two types of IRMOFs that own the same network topology, namely IRMOF-1 and its aminated version IRMOF-3, are embedded with CNF to fabricated TENGs; their contribution to triboelectric output enhancement, including the roughness effect induced by large particles as well as the charge induction effect arisen from -NH₂ groups, are discussed. The performance-enhanced CNF-based TENG with 0.6 wt.% of IRMOF-3 is utilized to harvest mechanical energy from human activities and charge commercial capacitors, from which the electrical energy is sufficient to light up light-emitting diodes (LEDs) and drive low-power electronic devices. In addition, a locomotor analysis system is established by assembling the above TENGs and capacitors into a 3 × 3 sensing array, which allowed signal extraction from each sensing unit to display a motion distribution map. These results demonstrate the great potential of CNF/IRMOF-based TENGs for development of self-powered sensing devices for long-term motion monitoring. Full article

The integration of biopolymers with antimicrobial inorganic materials has emerged as a promising strategy for developing eco-friendly and biocompatible functional materials for food packaging and biomedical applications. However, the impact of biopolymer matrix composition on the antimicrobial efficacy of inorganic fillers remains underexplored. This study addresses this critical gap by investigating the effects of chitin or chitosan oligosaccharides (NACOS or COS) on the antimicrobial properties of sodium alginate (SA)/cuprous oxide (Cu₂O) composite gels. The composite gels were synthesized through a physical blending of the components, followed by calcium-induced crosslinking of SA. Characterization using UV-vis, FTIR, and EDX confirmed the successful incorporation of Cu₂O, while a SEM analysis revealed its uniform dispersion. Antibacterial assays demonstrated that SA-Cu₂O exhibited the highest inhibition rates, with a 67.4 ± 11.9% growth suppression of Staphylococcus aureus (MRSA), 33.7 ± 5.1% against Escherichia coli, and 39.1 ± 14.8% against Pseudomonas aeruginosa. However, incorporating NACOS and COS reduced inhibition, as oligosaccharides served as bacterial carbon sources. Swelling and contact angle measurements indicate that antimicrobial effectiveness was independent of surface hydrophilicity. These findings underscore the importance of rational composite design to balance bioactivity and material stability for antimicrobial applications. Full article

This review explores the evolving landscape of sustainable textile manufacturing, with a focus on rubber-based materials for various industrial applications. The textile and rubber industries are shifting towards eco-friendly practices, driven by environmental concerns and the need to reduce carbon footprints. The integration of sustainable textiles in rubber-based products, such as tires, conveyor belts, and defense products, is becoming increasingly prominent. This review discusses the adoption of natural fibers like flax, jute, and hemp, which offer biodegradability and improved mechanical properties. Additionally, it highlights sustainable elastomer sources, including natural rubber from Hevea brasiliensis and alternative plants like Guayule and Russian dandelion, as well as bio-based synthetic rubbers derived from terpenes and biomass. The review also covers sustainable additives, such as silica fillers, nanoclay, and bio-based plasticizers, which enhance performance while reducing environmental impact. Textile–rubber composites offer a cost-effective alternative to traditional fiber-reinforced polymers when high flexibility and impact resistance are needed. Rubber matrices enhance fatigue life under cyclic loading, and sustainable textiles like jute can reduce environmental impact. The manufacturing process involves rubber preparation, composite assembly, consolidation/curing, and post-processing, with precise control over temperature and pressure during curing being critical. These composites are versatile and robust, finding applications in tires, conveyor belts, insulation, and more. The review also highlights the advantages of textile–rubber composites, innovative recycling and upcycling initiatives, addressing current challenges and outlining future perspectives for achieving a circular economy in the textile and rubber sectors. Full article

Polyurethanes (PUs) are extremely versatile materials used across different industries. Traditionally, they are synthesized by reacting polyols and isocyanates, both of which are petroleum-derived reagents. In response to the demand for more eco-friendly materials, research has increasingly focused on developing new routes for PU synthesis using renewable feedstocks. While substituting isocyanates remains a greater challenge, replacing fossil-based polyols with bio-based alternatives is now a promising strategy. This review explores the main natural sources and their transformations into bio-polyols, the incorporation of bio-fillers into PU formulations, and the production of non-isocyanate polyurethanes (NIPUs). Additionally, the study summarizes the growing body of research that has reported successful outcomes using bio-polyols in PU foams for distinct applications. Full article

Food packaging plays a crucial role in preserving freshness and prolonging shelf life worldwide. However, traditional packaging primarily acts as a passive barrier, providing limited protection against spoilage. Packaged food often deteriorates due to oxidation and microbial growth, reducing its quality over time. Moreover, the majority of commercial packaging relies on petroleum-derived polymers, which add to environmental pollution since they are not biodegradable. Growing concerns over sustainability have driven research into eco-friendly alternatives, particularly natural-based active packaging solutions. Among the various biopolymers, cellulose is the most abundant natural polysaccharide and has gained attention for its biodegradability, non-toxicity, and compatibility with biological systems. These qualities make it a strong candidate for developing sustainable packaging materials. However, pure cellulose films have limitations, as they lack antimicrobial and antioxidant properties, reducing their ability to actively preserve food. To tackle this issue, researchers have created cellulose-based active packaging films by integrating bioactive agents with antimicrobial and antioxidant properties. Recent innovations emphasize improving these films through the incorporation of natural extracts, polyphenols, nanoparticles, and microparticles. These enhancements strengthen their protective functions, leading to more effective food preservation. The films are generally classified into two types: (i) blend films, where soluble antimicrobial and antioxidant substances like plant extracts and polyphenols are incorporated into the cellulose solution, and (ii) composite films, which embed nano- or micro-sized bioactive fillers within the cellulose structure. The addition of these functional components enhances the antimicrobial and antioxidant efficiency of the films while also affecting properties like water resistance, vapor permeability, and mechanical strength. The continuous progress in cellulose-based active packaging highlights its potential as a viable alternative to conventional materials. These innovative films not only extend food shelf life but also contribute to environmental sustainability by reducing reliance on synthetic polymers. This review deals with the development of functional biopolymer films with antimicrobial and antioxidant properties towards sustainable food packaging. Full article