Search Results (363)

In this work, poly(acrylic acid)-based layers were injected to form a sandwich layer between the cationic and anionic species for a compact and effective fire-retardant coating on cotton fabric using the layer-by-layer coating technique. From the SEM analysis, as the number of tri-layers increases, the attachment intensity increases, as can be seen for poly(acrylic acid) chitosan and bentonite clay PCB-5TL (the highest tri-layers), while in the case of halloysite-based coatings, as the number of tri-layers increases, instead of attachment, the agglomeration increases due to the high surface area of halloysite nanoclay tubes. FTIR and UV confirmed the finding from the new peak entry and an increase in thickness. The highest thermal residue, ~18%, was obtained for poly(acrylic acid) chitosan and halloysite nanoclay PCH-5TL with a maximum degradation peak intensity at ~389 °C. From the flammability and after-burning SEM investigation test, it was observed that the halloysite-based coating with a higher number of layers offered higher resistance against the flame spread and ignition and, thus, produced a higher amount of char. Full article

The valorization of agro-industrial byproducts through pyrolysis represents a sustainable route for generating multifunctional raw materials within the framework of a circular bioeconomy. In this study, rice husk (RH) and sugarcane bagasse (SCB) were pyrolyzed in a semi-continuous reactor at 500 °C in order to compare product yields and to characterize resulting gas, aqueous and tar fractions. SCB produced the highest bio-oil yield (44.2 wt%), whereas RH generated the highest char yield (42.9 wt%), consistent with its higher ash and lignin contents. In both cases, tar represented about 12 wt% of the bio-oil. Detailed characterization revealed that the liquid products contained oxygenated compounds of interest, mainly carboxylic acids, ketones, and phenols. Acetic acid was the predominant compound in the aqueous phases, while tars were composed mainly of phenols, ketones, furans, and acids. Particularly, phenols accounted for 52.6% and 37.8% of the total chromatographic area in RH and SCB tars, respectively, whereas ketones represented about 10% in both cases. These results show that pyrolysis of agro-industrial residues not only enables energy recovery but also provides liquid fractions enriched in value-added chemicals. Full article

Mass timber elements such as glued laminated timber (Glulam) and cross-laminated timber (CLT) have become increasingly prominent in sustainable construction due to their structural efficiency and reduced environmental impact. However, fire performance remains a critical consideration for structural safety. This paper presents a comparative assessment of experimentally measured and code-predicted fire performance parameters for Glulam and CLT, including charring rate, effective charring depth, zero-strength layer (ZSL) thickness, and residual mechanical properties. The evaluation covers major international fire design standards: Eurocode 5 (EC5), the Australian Standard (AS/NZS 1720.4), the Swedish Handbook (Swedish), American Wood Council (AWC TR10), and the Canadian Standard (CSA O86). Across all Glulam datasets, charring rate predictions agreed with tests within approximately ±20%, while AS/NZS 1720.4 consistently over predicted charring and effective char depth by around 40%. In contrast, CLT demonstrates greater variability, primarily due to adhesive degradation, delamination, and lamella orientation, which influence heat transfer and post-fire capacity. CLT data exhibited higher scatter, with effective charring depth showing standard deviations of approximately 30 to 40%, ZSL thickness averaging about 2.5 times the typical 7 mm assumption, and residual stiffness commonly reducing to around 20 to 25% of initial values after standard fire exposure. Overall, findings suggest that current standards adequately address Glulam performance but require refinement to capture the complex fire response of CLT. Continued experimental research and targeted code development, particularly within the Australian Standard, are essential to improve reliability and confidence in performance-based fire design for mass timber structures. Full article

Waste biomass represents both an environmental pollutant and a potential renewable energy source. This study examines the feasibility of hydrogen production from tea residue biomass and solid waste, focusing on pyrolysis-based hydrogen generation. Compared to atmospheric pyrolysis, vacuum conditions reduce the saturated vapor pressure of biomass volatiles, thereby promoting char gasification, gas-phase interactions, and secondary tar cracking. Utilizing a self-designed vacuum-pyrolysis-catalysis system, we investigated the effects of key parameters—vacuum level, temperature, catalyst-to-feedstock ratio, and retention time on pyrolysis product distribution and formation mechanisms. Results indicate that Ni was successfully and uniformly loaded onto waste calcium oxide desiccant (DC) support via impregnation, thereby significantly increasing the specific surface area of the catalyst. Optimization using response surface methodology identified the following optimal conditions: pressure of 5 kPa, temperature of 835.89 °C, catalyst/feedstock ratio of 110.02%, and retention time of 2.35 h. Under these conditions, a hydrogen yield of 256.39 mL·g⁻¹ was achieved, corresponding to 95.3% of the simulated value. The process not only enabled efficient hydrogen production but also simultaneously yielded bio-oil and biochar, thereby facilitating carbon capture and recycling. These findings provide valuable insights into the resource-oriented application of vacuum pyrolysis-catalysis technology to waste biomass. 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

Silica-rich rice husk ash (RHA) was upcycled as an inorganic filler to engineer cellulose acetate (CA) films with tunable properties for higher-value sustainable packaging. Composite films were produced by solvent casting, varying RHA loading with and without glycerol plasticization. FTIRconfirmed the chemical integrity of CA and indicated an increase in hydroxyl interactions in glycerol-plasticized films. Optical microscopy showed that RHA progressively induces particle domains and aggregation, while glycerol improves dispersion and surface uniformity. These microstructural effects translated into controllable optical–mechanical trade-offs: neat CA remained highly transparent, whereas RHA reduced transmittance. Glycerol had a minor effect effect on transmittance, indicating that shielding is primarily governed by the ash-derived inorganic domains and tensile testing highlighted an optimal low-filler regime. A small RHA addition maximized strength and stiffness in non-plasticized films. Contact-angle measurements in neutral and alkaline media indicated pH-sensitive wetting, with faster deterioration under alkaline conditions. Thermogravimetric analysis confirmed increased char residue with RHA addition and that glycerol introduces an early mass-loss stage. Overall, the CA/RHA platform offers a simple and potentially scalable route to upcycled, silica-reinforced films, and the formulation of CA and 1.33 wt% RHA (without glycerol) stands out as a robust secondary layer with low transmittance in the UV-Vis range, making it suitable for high-value light-sensitive flexible healthcare packaging, such as protective overwraps or translucent pouches. Full article

To overcome the typical limitations of conventional polyurethanes, including insufficient thermal stability, mechanical strength, and recyclability, this study presents a high-performance and reprocessable poly(urethane–urea) nanocomposite reinforced with Ti₃C₂T_x MXene (MX-AHPU). The formation of strong hydrogen bonds between the urea groups of the polymer and the oxygen-functionalized MXene surface was confirmed by FTIR, XRD, and XPS, which also verified the complete reaction of –NCO groups. MXene incorporation substantially improved thermal stability, as evidenced by TGA showing a higher onset decomposition temperature and increased char residue. DSC analysis indicated a raised glass transition temperature, reflecting restricted chain mobility. The composite demonstrated remarkable mechanical enhancement, with tensile strength increasing by 70% to 26.7 MPa and toughness rising by 28% to 311.8 MJ·m⁻³, while maintaining exceptional elongation (>3600%). Dynamic mechanical analysis revealed a lower activation energy for stress relaxation (26.6 kJ/mol for MX-AHPU, 30.9 kJ/mol for neat AHPU), indicating enhanced molecular mobility and energy dissipation. Importantly, the material exhibited excellent recyclability, retaining most of its mechanical performance after three reprocessing cycles due to the reversible nature of the interfacial hydrogen bonds. This work provides an effective strategy for designing sustainable, high-performance polyurethane–urea composites suitable for demanding applications such as flexible electronics and advanced coatings. Full article

Biomass chemical looping gasification coupled with CO₂ splitting (BCLGCS) presents a promising carbon-negative route for simultaneous syngas production and CO₂ utilization, where the selection of oxygen carriers (OCs) is critical. Compared to single-metal oxides, composite metal OCs offer thermodynamic advantages. This study aims to evaluate the thermodynamic performance of composite metal OCs (LaFeO₃, BaFeO₃, CaFe₂O₄, and Ca₂Fe₂O₅) in BCLGCS to overcome the thermodynamic limitations of conventional biomass-CO₂ gasification. Gibbs free energy minimization calculations were performed to predict gas compositions and oxygen carrier phase transformations under varying operating conditions. Results show that steam addition promotes gasification by increasing H₂ content and lowering required temperatures, but substantially reduces CO₂ conversion in the splitting reactor by consuming residual char. Ca₂Fe₂O₅ demonstrates superior adaptability with tunable H₂/CO ratios, while LaFeO₃ requires high OC loading and BaFeO₃ undergoes deactivation via BaCO₃ formation. This work reveals inherent thermodynamic conflicts between gasification and CO₂ splitting steps, indicating that the optima for syngas production and CO₂ utilization are mutually exclusive, an insight not previously quantified in BCLGCS literature. The findings provide theoretical guidance for designing carbon-tolerant OCs and optimizing process parameters, advancing BCLGCS toward practical carbon-negative applications. Full article

Textile waste management remains a critical environmental challenge. Valorization through thermochemical routes such as pyrolysis offers a sustainable pathway within the circular economy. In this study, carbonaceous materials were obtained from the pyrolysis of 100% cotton textile residues and subsequently activated with sodium thiosulfate (Na₂S₂O₃). The physicochemical and leaching behaviors of the activated (CA) and non-activated (C) chars were assessed in aqueous solution under controlled pH conditions (3, 7, and 11). Activation significantly increased the specific surface area (from 90 to 975 m² g⁻¹). Leaching tests revealed that acidic conditions (pH = 3) enhanced the release of major elements following the order Na > Ca > K for C and S > Ca > Na for CA. Despite this, all concentrations of major and trace metals remained well below regulatory discharge limits. Anionic species (Cl⁻, SO₄²⁻) increased slightly after activation but also stayed within safe thresholds, and chemical oxygen demand (COD) values were low (0–9 mg O₂ L⁻¹), indicating negligible organic leaching. Overall, the findings show that the structural quality of textile-derived chars was improved by Na₂S₂O₃ activation without compromising their environmental stability, validating their applicability as effective and safe adsorbents for wastewater treatment applications. Full article

EPDM is widely used as the polymer matrix for solid rocket motor (SRM) internal thermal protection because of its low density, chemical inertness, and ability to form carbonaceous residue. Practical performance is frequently limited by weak char integrity and barrier properties, char oxidation, mechanical stripping in gas-dynamic flow, and by the poor comparability of published results due to non-uniform test conditions and reporting. This review systematizes studies on 0D nanofillers in EPDM ablatives and harmonizes the key metrics, including linear and mass ablation rates (LAR, MAR), back-face temperature (T_back), and solid residue yield. The major 0D additives-nSiO₂, nTiO₂, nZnO, and carbon black (CB) are compared, and their dominant mechanisms are summarized: degradation-layer structuring, reduced gas permeability, thermo-oxidative stabilization, and effects on vulcanization. Several studies report larger improvements for hybrid systems, where CB enhances char cohesion and retention, while oxide nanoparticles improve barrier performance and resistance to oxidation. Finally, an application-oriented selection matrix is proposed that accounts for thermal protection efficiency, processability, agglomeration limits, and density penalties to support EPDM coating design and improve comparability. Full article

Flame-retardant microcapsules were prepared using a urea–melamine–formaldehyde (UMF) shell and boric acid-crosslinked ammonium polyphosphate (APP) as the core to improve the dispersion stability and processing compatibility of phosphorus-based flame retardants. Thermal analysis showed that the microcapsules exhibited initial mass loss near 80 °C due to moisture evaporation and shell relaxation, while APP-related degradation occurred at higher temperatures, indicating delayed release of the core and enhanced thermal resistance through encapsulation. Scanning electron microscopy confirmed the formation of microcapsules, and morphological changes before and after combustion suggested the development of protective char layers. Boron-containing residues are expected to contribute to char stabilization through the formation of B–O–P structures during heating. The flame-retardant properties were evaluated using limiting oxygen index, smoke density, and vertical burning tests. Although the limiting oxygen index slightly decreased due to reduced accessible APP content, stable burning behavior was maintained, and characteristic char formation was observed after combustion. These results indicate that the UMF/APP microcapsules can improve thermal stability and handling of phosphorus-based flame retardants. The microencapsulation approach presented here may provide practical advantages for polymer processing and surface-coating applications. Full article

This manuscript reports the preparation, surface characterization, and modeling of chars and activated carbons obtained from avocado biomass for hydrogen storage. Activated carbons were prepared from avocado biomass via the following stages: (a) pyrolysis of avocado biomass, (b) impregnation of the avocado-based char using an aqueous lithium solution, and (c) thermal activation of lithium-loaded avocado char. The synthesis conditions of char and activated carbon samples were tailored to maximize their hydrogen adsorption properties at 77 K, where the impact of both pyrolysis and activation conditions was assessed. The hydrogen storage mechanism was discussed based on computational chemistry calculations and multilayer adsorption simulation. The modelling focuses on the analysis of the saturation of activated carbon active sites via the adsorption of multiple hydrogen molecules. The results showed that the activated carbon samples displayed adsorption capacities higher than their char counterparts by 71–91% because of the proposed activation protocol. The best activated carbon obtained from avocado residues showed a maximum hydrogen adsorption capacity of 142 cm³/g, and its storage performance can compete with other carbonaceous adsorbents reported in the literature. The hydrogen adsorption mechanism implied the formation of 2–4 layers on activated carbon surface, where physical interactions via oxygenated functionalities played a relevant role in the binding of hydrogen dimers and trimers. The results of this study contribute to the application of low-cost activated carbons from residual biomass as a storage medium in the green hydrogen supply chain. Full article

The objective of this study was to establish the kinetic of gasification reactions involved in chemical looping gasification (CLG) using pelletized biomass as solid fuel. However, significant limitations have been found in obtaining such kinetics using a traditional methodology from a large number of tests in a thermogravimetric analyzer (TGA) for pelleted biomass. A novel methodology is presented in this article, namely: (i) the determination of the intrinsic gasification rate for several biomasses; (ii) the determination of the gasification rate of pelletized biomass under selected operating conditions; (iii) the development and validation of a reaction model for pelletized biomass considering the determined intrinsic kinetics and gas diffusion in the biomass particles; and (iv) obtaining an apparent kinetics from data calculated with the developed model, which will be easy to implement in the modeling of gasifiers. To evaluate the applicability of this methodology, it was demonstrated with three different types of biomasses: pine forest residue (PFR), industrial wood pellets (IWP), and wheat straw pellets (WSP). The intrinsic kinetics was derived from tests with powdered char under several operating conditions: reacting temperature (1073–1223 K), concentration of gasifying agent (10–40 vol.% H₂O or CO₂), and concentration of gasification product (0–40 vol.% H₂ or CO). The evolution of the char conversion with the reacting time was predicted using a model involving three different regimes: (I) deactivation at the beginning; (II) uniform progress in the main middle part following a n-order model; and (III) catalytic activation as complete conversion is approached. The second regime was included for all biomasses, being 1, 0.4, and zero-order for WSP, IWP, and PFR, respectively. However, the third regime was observed for PFR and IWP, and the first regime only for IWP. The intrinsic kinetics was successfully used in a theoretical model to properly predict the gasification rate of pelletized biomass, and, eventually, to determine an apparent gasification kinetics as simple as possible in order to be easily implemented in future gasifier modeling works. Full article

This work aimed to investigate the thermal properties of phosphorus-modified epoxy resin obtained from eugenol derivatives and cured with different amines: aliphatic—triethylenetetramine (TETA); aromatic—diaminodiphenylmethane (DDM); and cycloaliphatic—isophoronediamine (IDA). The thermal stability was investigated through both thermogravimetric analysis (TGA) coupled to a Fourier transform infrared spectrometer (TGA/FTIR) and pyrolysis–combustion flow calorimetry (PCFC). The structures of the cured castings and the char residues were assessed by scanning electron microscopy (SEM). Eugenol-based resin during thermal degradation is covered with a significant amount of char residue and is characterized by a reduced value of heat release rate (HRR) and heat release capacity (HRC) compared with the resin based on petrochemicals. Full article

Phosphorus-modified poly(vinyl alcohol) (PVA) has recently gained increasing attention as a functional polymeric matrix suitable for gel-based systems, owing to its biocompatibility, film-forming ability, and capacity to develop semi-interpenetrating networks. In this work, PVA was chemically modified through the nucleophilic substitution of its hydroxyl groups with the chloride groups of phenyl dichlorophosphate, following a literature-reported method carried out in N,N-dimethylformamide (DMF) as reaction medium, resulting in phosphorus-containing PVA networks (PVA-OP3). Hybrid gel-like films were then prepared by incorporating titanium dioxide nanoparticles (TiO₂ NPs), known for their antimicrobial activity, low toxicity, and high stability. The resulting composites were structurally, morphologically, and thermally characterized using FTIR, SEM, and thermogravimetric analysis. The incorporation of TiO₂ NPs significantly improved the thermal stability, with T₅% increasing from 240 °C for neat PVA-OP3 to 288 °C for the optimal composite, increased the char residue from 4.5% for the neat polymer to 30.1% for PVA-OP3/TiO₂-4, and enhanced antimicrobial activity against both Gram-positive and Gram-negative bacteria. These findings demonstrate that PVA-OP3/TiO₂ hybrid films possess promising potential as advanced biomaterials for biomedical, protective, and environmental applications. Full article