Search Results (160)

We co-modified layered double hydroxide (LDH) in water using phosphocreatine (PC) and dodecylphosphoric acid (DPA) to obtain a highly dispersible LDH. Embedding this LDH in epoxy enabled V-0 at 7 wt% and lowered HRR, THR and TSP, attributed to a dense char and PC-DPA synergy. SEM, WAXS, and TGA characterised the structure and thermal behaviour of the functionalised LDHs. These modified LDHs were then loaded into the epoxy resin (EP) to develop flame-retardant nanocomposites. Compared to unmodified LDH (NO₃-LDH) and PC-modified LDH (PC-LDH), PC-DPA-LDH showed superior dispersion and compatibility within the epoxy matrix. As a result, PC-DPA-LDH/EP achieved a UL-94 V-0 rating at only 7 wt% loading, while NO₃-LDH/EP had no rating, and PC-LDH/EP reached only V-2. Moreover, PC-DPA-LDH/EP demonstrated significant decreases in peak heat release rate (46.4%), total heat release (34.5%), and total smoke production (59.7%) compared with neat EP. These improvements were attributed to the synergistic flame-retardant effects of PC and DPA, as well as to the formation of a compact char layer that effectively insulated the underlying material and suppressed volatile emissions. This work highlights the potential of bio-based, aqueous-synthesised nanohybrids for high-efficiency, eco-friendly flame-retardant epoxy systems. Full article

This review examines how plant polyphenols enable multifunctional textiles, offering a sustainable alternative to synthetic dyes and nanomaterial-based treatments. A literature search (2001–2025) identified 105 peer-reviewed studies across eight functional areas. Abundant in agricultural and industrial byproducts, plant polyphenols act as natural colorants, bio-adhesives, and performance enhancers—providing coloration, antibacterial activity, UV protection, flame retardancy, deodorization, antioxidant capacity, superhydrophobicity, and more. Their catechol and pyrogallol groups bind strongly to natural and synthetic fibers via hydrogen bonding, π–π stacking, and metal chelation, ensuring durable, nontoxic functionality. We analyze structure–function links and scalable methods, including pad-dry-cure and metal–phenolic network (MPN) assembly, which were validated against ISO, ASTM, and AATCC standards. Polyphenol-based textiles match or exceed conventional ones in key metrics, with added benefits: full biodegradability, low ecotoxicity, and skin compatibility. Key advances include enzymatic polymerization for wash-stable color, MPN tuning for customizable functions, and using waste-derived polyphenols. However, major challenges remain: narrow color range (mostly yellow, brown, black) and poor wash/UV resistance, leading to rapid fading and loss of antibacterial/UV protection after laundering. Solving these is a top priority for future work. Overall, this review delivers a practical, science-based roadmap for high-performance, sustainable textiles that align with the Sustainable Development Goals and meet real-world needs in healthcare, sportswear, and smart wearables. Full article

Environmental fires pose a serious threat to energy security, ecosystems and public safety, whilst traditional halogenated flame retardants suffer from limitations such as high environmental residue risks and insufficient flame-retardant efficacy. In this study, sodium alginate (SA) was utilised as the matrix, with the incorporation of ammonium polyphosphate (APP) and phytic acid (PA), in conjunction with SiO₂-APTES surface modification, to prepare nitrogen–phosphorus synergistic bio-based flame-retardant gels. The present study systematically investigated the influence of the N/P molar ratio on the gelation kinetics, rheological behaviour, microstructure and flame-retardant performance of the gel. The study revealed a nitrogen–phosphorus coupled gas–solid two-phase synergistic flame-retardant mechanism. The results indicate that at an N/P ratio of 1/4, the gel forms a stable dual-network structure comprising ionic cross-links and Si–O–P covalent bonds. In the gas phase, the thermal decomposition of APP releases inert NH₃, which dilutes oxygen and quenches gas-phase radicals (·OH, ·H). In the condensed phase, the phosphate groups of PA-catalysed SA form Si–O–P covalent bonds with SiO₂ under the mediation of APTES, creating a dense, insulating char layer. In comparison with the control group (N/P = 0/0), the optimal gel sample (N/P = 1/4) demonstrated a 33% increase in shear stress, a 10% reduction in the peak heat release rate (HRR), a 75% decrease in total smoke production (TSP), and a 150% increase in char layer thickness after combustion, while maintaining adequate mechanical strength, thermal stability, and environmental friendliness. This work provides novel insights and strategies for the development of green, highly efficient flame-retardant materials for environmental fire prevention and control. Full article

Natural fibers are among the most extensively exploited bio-based materials in industry due to their abundance, affordability, and biodegradability. However, their intrinsic properties often require improvement through chemical, mechanical, or enzymatic treatments to expand their applications. Phosphorylation is a highly effective chemical modification that enables the covalent grafting of phosphate groups onto the fiber backbone. These functionalities enhance hydrophilicity, anionic charge density, swelling capacity, and water uptake, while significantly improving flame-retardant performance. In addition, phosphorylation can reduce energy consumption and production costs in the manufacture of functionalized micro- and nanofibrillated fibers, as the increased swelling facilitates fibrillation. Consequently, phosphorylated fibers are suitable for water treatment, biomedical devices, construction materials, and other advanced materials. Dozens of reagents and various synthetic routes have been explored to perform this reaction, each producing materials with distinct properties. Phosphorus content remains the primary parameter used to assess modification efficiency. This literature review examines existing phosphorylation methods, including reagents, substrates, and characterization techniques, and discusses applications such as flame retardancy, thermal insulation, ion exchange, energy storage, electrodes, and battery recycling. It also briefly addresses key challenges, including limited hydroxyl accessibility, control of the degree of substitution, potential cellulose degradation, and scalability constraints. Full article

Background: The transition from fossil-derived polymer additives to renewable alternatives is essential to mitigate environmental persistence and ensure chemical safety within the plastics industry. This review provides a comprehensive overview of recent developments in bio-based functional additives and their integration into circular economy frameworks. Methods: Following PRISMA guidelines, a systematic literature search was conducted using the Scopus database for studies published between 2023 and 2026. Search terms targeted bio-based plasticizers, flame retardants, antioxidants, and compatibilizers. Studies were screened against predefined inclusion criteria, specifically focusing on experimental validation in polymer matrices, while data mining was employed to map emerging research fronts. Results: From an initial 996 records, 54 studies were selected after removing duplicates and ineligible articles. The findings highlight a paradigm shift from passive physical fillers toward active, multifunctional macromolecular agents. Recent literature demonstrates that targeted molecular interventions, such as phosphorylated lignin and biomimetic structures, can resolve trade-offs between ductility and thermal stability at low loadings (<5 wt%). Synthesis routes, performance outcomes, and end-of-life trajectories for each additive class are summarized. Conclusions: Bio-based additives have evolved from simple substitutes into strategic tools for the molecular programming of sustainable polymers. Although challenges regarding scalability and high-temperature processing persist, their integration into circular economy strategies establishes a clear roadmap for next-generation bioplastics. Full article

Scalable halogen-free flame-retardant textile finishes remain challenging, particularly regarding laundering durability and industrially viable processing. Here, two phytate flame retardants, poly(vinylammonium) phytate (PVAmPA, partly bio-based) and chitosan phytate (ChiPA, fully bio-based), were applied to cotton (CO), polyester (PET), and a CO/PET blend by a single-step, binder-assisted coating. Both coatings suppressed surface flaming in ISO 15025 on all substrates. Although laundering at 40 °C caused systematically higher wash-off for ChiPA, surface flame suppression was retained for most coated fabrics, with the exception of ChiPA on CO and PVAmPA on PET. Thermogravimetric analysis showed earlier decomposition and increased residue formation for both systems, with the residue at 700 °C increasing from 4.5% to 18.2% for CO_PVAmPA and from 4.5% to 15.2% for CO_ChiPA. In microscale combustion calorimetry, PVAmPA reduced the heat release capacity (HRC) from 251 to 168 J/(g·K) for CO/PET, whereas ChiPA showed its strongest effect on PET, reducing HRC from 413 to 222 J/(g·K). Gas-phase analyses indicated enhanced water release for both coatings and additional NH₃ evolution for PVAmPA. Overall, binder-assisted, single-step phytate coatings provide a scalable route to halogen-free flame retardancy, with PVAmPA showing the most robust overall durability and ChiPA offering a fully bio-based alternative with strong substrate-dependent performance. Full article

This work focused on the investigation of sulfonated lignin as a novel and sustainable reinforcing filler for polyamide 6 (PA6) composites. Different formulations were thus prepared by melt compounding, varying the lignin content (5, 10, and 20 wt%). The interaction between lignin and PA6 was systematically studied through rheological, structural, morphological, thermo-mechanical, and flammability tests. Rheological measurements showed an increase in the complex viscosity and viscoelastic moduli with increasing lignin content, suggesting restricted polymer chain mobility and the formation of strong physical interactions between the molten PA6 and the lignin particles. Microstructural observations through FESEM highlighted a good dispersion of lignin particles and efficient filler–matrix interfacial adhesion. Moreover, the addition of lignin significantly increased the tensile stiffness of the composites (up to 3.4 GPa), and a lignin content of 10 wt% enhanced the tensile strength up to 58.4 MPa (i.e., +45% compared to neat PA6) without compromising the ductility. Finally, UL-94 tests revealed an improvement in flame retardancy at higher lignin contents due to the intrinsic char-forming ability of this filler. These results demonstrated that lignin could be an effective multifunctional bio-based filler that can improve the thermo-mechanical performance of PA6 without the need for compatibilizing agents. Full article

Phytic acid (myo-inositol hexakisphosphate) and its salts, including iron, aluminum, sodium, and lanthanum phytate, are perhaps the most recent discovery in the field of bio-sourced flame retardants. Phytic acid can be extracted from sustainable resources, such as beans, cereals, and oilseeds. Its high phosphorus content (28 wt.% based on molecular weight) organized into six phosphate groups justifies the growing interest this biomolecule has attracted over the last decade in various sectors (as a corrosion inhibitor, antioxidant, and anticancer additive, among others). In addition, when exposed to a flame or an irradiative heat flux, phytic acid is a highly efficient dehydrating and char-forming agent. It also contributes to excellent flame-retardant properties when combined with other carbon sources, such as chitosan, or nitrogen-containing additives, including melamine, urea, and polyethyleneimine. This paper reviews the most recent advances in using phytic acid and its derivatives to design effective flame-retardant systems for textiles, bulk polymers, and foams. It also provides perspectives on possible future developments and implementations. Full article

The increasing demand for sustainable and environmentally friendly construction materials has spurred interest in biopolymer composites reinforced with agricultural waste. Rice husk (RH), a byproduct of rice milling, is abundant and rich in lignocellulosic fibers and silica, making it excellent for use in fiber-reinforced biopolymers. The novelty of this study lies in its integrated and construction-oriented evaluation of rice husk (RH)-reinforced biopolymers, combining mechanical, thermal, environmental, and economic perspectives within a single framework. The study introduces a novel comparative approach by benchmarking multiple polymer matrices-including PP, recycled HDPE, epoxy, PLA, and bio-binders-under unified quantitative performance criteria. Another key novelty is the identification of the dual functional role of silica-rich RH in simultaneously enhancing structural strength and flame retardancy while contributing to carbon emission reduction. With a high silica content (15–20%) and lignocellulosic structure, RH serves as a natural filler that enhances the performance of polymer matrices such as polypropylene (PP), epoxy, polylactic acid (PLA), and recycled polyethylene. Mechanically, RH-reinforced composites demonstrate significant improvements in tensile, flexural, and impact strength. For example, PP composites with NaOH-treated RH and coffee husks achieved tensile strengths between 27.4 MPa and 37.4 MPa, with corresponding Young’s modulus values ranging from 1656 MPa to 2247.8 MPa. Recycled HDPE-RH blends reached tensile strengths up to 74 MPa and flexural values of 39 MPa, validating their structural applicability. Epoxy matrices embedded with 0.45 wt.% RH nanofibers showed degradation thresholds of 411 °C and 678 °C, reflecting substantial thermal resistance. Flame retardancy is further improved by the presence of RH biochar, which leads to reduced peak heat release rate (PHRR) and enhanced char formation. In building insulation applications, RH-based composites exhibit low thermal conductivity values between 0.08 and 0.14 W/m·K, contributing to energy efficiency. Economically, RH reduces material costs by 30–40%, while environmentally, its integration lowers carbon emissions in PP composites by up to 10%, and promotes biodegradability. Despite challenges such as moisture absorption and interfacial adhesion, these can be mitigated through alkali treatment, compatibilizers (e.g., MAPP), or hybrid reinforcement strategies. Full article

Cotton fabrics are widely used in textiles due to their comfort and breathability, but their high flammability (limiting oxygen index (LOI) ≤ 18%) poses serious safety risks. While conventional flame-retardant treatments often rely on synthetic chemicals or toxic additives, biobased alternatives remain underdeveloped. The flame resistance of cotton fabrics may be enhanced using multilayer biocoatings of chitosan and sodium alginate applied via layer-by-layer (LBL) assembly—a sustainable and scalable approach. Cotton samples were coated with chitosan and sodium alginate bilayers (1, 2, 5, and 10 layers) using the LBL method. Flame resistance was evaluated using vertical flame tests and limiting oxygen index (LOI) testing according to ASTM D2863-09. The sample coated with 10 bilayers significantly outperformed uncoated cotton and lower-layer samples. With a char length of 9.72 cm (68% reduction), no dripping was observed in the vertical flame tests, and the LOI value was 23.47% compared to uncoated cotton (LOI = 18.04%). These improvements were attributed to the formation of a cohesive and protective carbon layer, which is likely capable of inhibiting the formation of flammable gases. Biomaterial multilayer coatings made from biomaterials, such as chitosan and sodium alginate, represent a promising and environmentally friendly alternative to traditional methods in improving cotton’s flame resistance. The development of this technology points to potential applications in protective textiles and industrial safety clothing. Notably, chitosan and sodium alginate coatings are biocompatible. The term “biomaterials” refers to materials intended for interaction with biological systems, particularly for biomedical-related applications. The term “biobased materials” is used exclusively to describe materials derived from renewable biological sources. Full article

This study presents a sustainable strategy for improving the thermal properties of pine wood through the application of calcium carbonate nanopowder (CCNP) chelated with polycarboxylic acids (citric acid (CA) and tartaric acid (TA)) as coatings. The chelation reaction was confirmed by the detection of carbon dioxide (CO₂) gas. CCNP was characterized using microscopy and particle size analysis. The formation of crystalline calcium citrate and calcium tartrate was verified using FTIR and Raman spectroscopies, and XRD analysis. Wood treatment was conducted using different volumetric ratios of CA and TA. The CA-TA-treated (coated) wood blocks achieved the highest mass gain after treatment of around 89%, while the pure TA treatment exhibited enhanced leaching resistance, maintaining around 69% mass gain after leaching test. TGA conducted under oxidative (air) conditions showed that the coatings promoted char formation and produced inorganic residues from 6.4% to 7.8%, with the control resulting in negligible residual mass. Flame retardancy tests showed that the chelated coatings effectively delayed combustion and inhibited heat transfer, with the TA treatment showing improved flame retardancy performance by limiting the surface temperature to ~200 °C after 60 s of exposure, as compared to >550 °C for the control. Full article

Natural-fiber biocomposites are increasingly viewed as promising materials for sustainable engineering. However, their broader adoption remains constrained by coupled challenges related to interfacial compatibility, moisture sensitivity, environmental durability, processing limitations, and end-of-life trade-offs. Rather than treating fiber selection, matrix chemistry, processing routes, durability, and sustainability as independent considerations, this review emphasizes their interdependence through the fiber–matrix interface, which governs stress transfer, moisture transport, and long-term property evolution. It provides a comprehensive and integrative analysis of natural-fiber–reinforced polymer composites, encompassing plant-, animal-, and emerging bio-derived reinforcements combined with bio-based, biodegradable, and selected synthetic matrices. Comparative analysis across the literature demonstrates that interfacial engineering consistently dominates mechanical performance, moisture resistance, and property retention, while mediating trade-offs among stiffness, toughness, recyclability, and biodegradability. Moisture transport and environmental ageing are examined using thermodynamic and diffusion-controlled frameworks that link fiber chemistry, interfacial energetics, swelling, and debonding to performance degradation. Fire behavior and flame-retardant strategies are reviewed with attention to heat-release control and their implications for durability and circularity. Processing routes, including extrusion, injection molding, compression molding, resin transfer molding, and additive manufacturing, are assessed with respect to fiber dispersion, thermal stability, scalability, and compatibility with bio-based systems. By integrating structure–property relationships, processing science, durability mechanisms, and sustainability considerations, this review clarifies how natural-fiber biocomposites can be designed to achieve balanced performance, environmental stability, and circular life-cycle behavior, thereby providing guidance for the development of systems suitable for near-term engineering applications. Full article

Research on tannin-based foams has shown promising results. However, all developments in this field have not been addressed from different perspectives, in a systematic way, and with an emphasis on sustainability. This work discusses different formulations, emphasizing their bio-based components and how modifications influence key properties. It examines life cycle assessment (LCA) studies through a sustainability lens and identifies major commercial phenolic products to highlight the practical use of tannin foams for thermal insulation. The type of tannins, as well as their sources, influences the key properties of these foams. The replacement of formaldehyde, a crosslinking agent known for its health risks, is possible, particularly through more sustainable alternatives that allow for foams with better properties than those obtained with formaldehyde. Substitution of diethyl ether with less hazardous alternatives results in foams with improved thermal and mechanical performance. The elimination of the blowing agent—the green alternative—also leads to foams with good performance. The presence of additives (surfactants, plasticizers, and fillers), some of which are sustainable, improves the mechanical properties of the foams. The performance in fire-related applications, already promising, is also enhanced by the presence of additives. An increase in understanding, combined with the sustainable nature of the various alternatives, makes tannin-based foams promising candidates for next-generation insulation and structural materials in construction. Full article

Bio-based bismaleimide (BMI) resins can reduce environmental impact and impart intrinsic flame retardancy, but achieving a high glass transition temperature (Tg) remains challenging. Here, we replace the conventional petrochemical co-monomer O,O′-diallyl bisphenol A (DABPA) with a synthesized tri-allyl derivative of curcumin (AEC) in 4,4′-bismaleimidodiphenylmethane (BDM)-based resins. The AEC monomer, synthesized via exhaustive O- and C-alkylation of curcumin, acts as a trifunctional crosslinker. By systematically varying the imide:allyl molar ratio, we optimized the network properties. We optimize the network’s thermal and fire-safety properties. The optimized formulation (BDM: AEC = 1:0.87, denoted BA-0.87) yields 43.06% char at 800 °C and reduces the peak heat release rate (PHRR) by 13.2% compared to the conventional BDM/DABPA control (BD-0.87). Meanwhile, BA-0.87 passes UL-94 V-0 with no dripping and attains a Tg above 400 °C—nearly 100 °C higher than BD-0.87. These enhancements arise from curcumin’s rigid conjugated structure, which increases crosslink density and promotes char formation during decomposition. Our work demonstrates a viable, bio-derived pathway to engineer BMI resins that simultaneously improve thermal stability and intrinsic flame retardancy. Such resins are promising for demanding aerospace and high-temperature electronic applications that require both fire safety and stability. Full article

Urban leaf litter represents an underutilized biomass resource with potential applications in sustainable building materials. This study investigates the suitability of dried, comminuted leaves collected from municipal green areas as a loose-fill thermal insulation material. The material was characterized in terms of thermal conductivity, settlement behavior, fire reaction, resistance to mold growth, water vapor diffusion, hygroscopic sorption, and short-term water absorption. Tests were conducted following relevant DIN and ISO standards, with both untreated and flame-retardant-treated samples examined. Results indicate that the thermal conductivity of leaf-based insulation (λ = 0.041–0.046 W/m·K) is comparable to other bio-based loose-fill materials such as cellulose and wood fiber. Optimal performance was achieved for particles sized 2–16 mm, showing settlement below 1%. All variants, including untreated material, fulfilled the fire resistance requirements of class E, while selected treatments further improved fire resistance. The material exhibited moderate vapor permeability (μ ≈ 4–5), low water absorption, and moisture buffering behavior similar to that of other bio-based insulation materials. Resistance to mold growth was satisfactory under standardized conditions. Overall, the results demonstrate that leaf litter can serve as an effective and environmentally favorable loose-fill insulation material, offering an innovative recycling pathway for urban green waste. Full article