Search Results (506)

The development of high-performance flame-retardant (FR) polypropylene (PP) with high mechanical integrity remains a challenge. Herein, we demonstrate a synergistic flame retardancy system for PP achieved via partial substitution of piperazine pyrophosphate (PAPP) with 1 wt.% magnesium borate whiskers (MBW) for improved flame retardancy, and thermal and mechanical properties. The optimized PP/24PAPP/1MBW exhibits exceptional FR performance, driven by the formation of a highly ordered, continuous phosphorus–boron hybrid char in the condensed phase. Cone calorimetry test results reveal an 80% reduction in peak heat release rate, a 54% reduction in total heat release, and a 33% reduction in total smoke production compared to neat PP, while the UL-94 test confirms a V-0 rating with complete suppression of flaming drips. Morphological study of the char residue using Raman spectroscopy and SEM attributes this performance to enhanced char graphitization and structural coherence enabled by boron-mediated cross-linking. More importantly, this transformative flame retardancy performance is achieved without severe compromise to mechanical properties, retaining over 89% of the original tensile strength. This work confirms the PAPP/MBW system as a highly efficient, low-additive approach to creating advanced fire-safe polymer composites for engineering applications. Full article

This study investigates the influence of surface-modified fly ash particles on the fire behavior of polyamide 6 (PA6) composites containing two types of flame retardants: melamine polyphosphate (MPP) and aluminum diethyl phosphinate (AlPi). The objective was to evaluate how interfacial modification of fly ash using amino-silane (APTES), glycidoxy-silane (GPTES), or titanate coupling agents affects dispersion, thermal stability, and combustion performance. A series of 18 formulations containing up to 25 wt% of additives was prepared by melt compounding and characterized by thermogravimetric analysis (TGA) and cone calorimetry. TGA results showed that MPP-based systems favored char formation, with residues up to 21%, whereas AlPi provided higher thermal stability (T₅₀% ≈ 445 °C). The incorporation of untreated or surface-treated fly ash improved both thermal stability and char yield, depending on the nature of the coupling agent. Cone calorimeter results confirmed a strong synergistic effect between flame retardants and fly ash. The peak heat release rate (pHRR) decreased by 65–75% compared to neat PA6, while total heat release (THR) and mass loss were also significantly reduced. Titanate-modified fly ash showed the most homogeneous dispersion and provided the highest residue and lowest pHRR values. Energy-dispersive X-ray (EDX) analyses confirmed enhanced phosphorus retention in the residues (up to 100%), evidencing the formation of stable inorganic species and protective ceramic-like structures. These results demonstrate that surface-modified fly ash can act as an efficient synergistic additive in PA6 flame-retardant formulations, simultaneously improving fire performance and promoting the valorization of industrial by-products for sustainable polymer design. Full article

Biomass, composed of natural polymers such as cellulose, hemicellulose, and lignin, can be converted into circular chemical feedstocks through thermochemical conversion processes like pyrolysis. Char conversion is the rate-limiting step in the thermochemical conversion process, and thus, char reactivity is essential for determining the overall efficiency of pellet-based thermochemical processes. Pyrolysis experiments were conducted on rice straw pellets of different sizes (i.e., 8, 10, and 12 mm) in a vertical quartz tube reactor at 700 °C, and then the chemical structure of chars sampled at different stages and locations within a 10 mm pellet was analyzed using Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results indicate that increasing the pellet size facilitates the growth of polycyclic aromatic structures, as evidenced by the observed variations in the abundance of typical aromatic compounds in bio-oil. This also promotes volatile–char interactions, leading to greater deposition of large aromatic structures on the char surface, thereby enhancing char aromatization. Analogous to the spatial scale effect of pellet size on char structure, the evolution of the char structure within a single pellet exhibits distinct spatial heterogeneity during the initial devolatilization and subsequent char aromatization stages due to the location-dependent coupling of heat/mass transfer limitations and aromatization reactions during pyrolysis. Furthermore, the spatiotemporal evolution of the char structure leads to differences in the specific reactivity: during the devolatilization stage at 75 s, the center exhibits the highest reactivity, whereas the outer surface becomes the most reactive in the subsequent char aromatization stage at 300 s. Full article

Accurate modeling of the burning rate of char particles in particle-laden flows is essential. However, because of the strong inhomogeneity and nonlinearity of the process, accurately resolving the surface burning rate of char particles remains challenging. In this study, an eXtreme Gradient Boosting (XGBoost)-based framework is developed to reformulate the conventional char oxidation rate model, namely the Baum&Street (B&S) model, resulting in a modified model referred to as the XGB-B&S model. In this model, a correction term ${\beta }_{\mathrm{turb}}$ is incorporated and formulated using the particle Reynolds number together with a dimensionless temperature. A turbulent mixing layer with char particle combustion is simulated by means of particle-resolved direct numerical simulation with three-dimensions, generating a high-fidelity dataset for model training and validation. To assess the predictive capability of the XGBoost model, its results are benchmarked against those obtained from an Artificial Neural Network model. The comparison indicates that XGBoost provides better overall accuracy, as reflected by a larger coefficient of determination (${\mathrm{R}}^2$) and smaller values of both the root mean square error and the mean absolute error. Finally, the XGB-B&S model is validated against the test dataset. The ${\mathrm{R}}^2$ between the XGB-B&S predictions and the PR-DNS results is significantly higher than that between the conventional B&S model and the PR-DNS results, confirming the strong predictive capability of XGBoost for modeling char particle oxidation rate. Full article

Epoxy resins (EP) are widely used in aerospace, electronics, and coatings due to their excellent mechanical and thermal properties. However, their inherent flammability and brittleness limit high-end applications. In this work, a novel reactive flame retardant epoxy monomer (EP-DVGA) containing DOPO and triazole units was designed and synthesized via a molecular engineering strategy. The chemical structure was confirmed by FTIR and NMR. A series of modified epoxy thermosets were prepared by co-curing EP-DVGA with bisphenol A epoxy resin (E51) using DDM as curing agent. The results showed that EP-DVGA significantly enhanced flame retardancy: At 16.31 wt% loading, the limiting oxygen index increased from 25.9% to 34.3% with UL-94 V-0 rating, and cone calorimetry revealed 73.2% and 69.2% reductions in peak heat release rate and total heat release, respectively. Mechanistic studies demonstrated a dual flame retardant effect involving phosphorus radical quenching in the gas phase and formation of a dense graphitized char layer in the condensed phase. Remarkably, EP-DVGA also improved mechanical properties—impact strength increased by 47% and tensile strength by 33.1% at optimal loadings—attributed to energy dissipation through reversible hydrogen bonding and π–π interactions. This molecular design successfully overcomes the traditional trade-off between flame retardancy and mechanical performance, offering a promising strategy for developing high-performance intrinsically flame retardant epoxy materials. Full article

The lack of centralized waste management infrastructure in certain regions makes plastic waste an escalating environmental and economic problem. This research investigates how modular portable pyrolysis systems function as sustainable decentralized solutions. A standard shipping container houses a custom-designed pyrolysis unit which demonstrates flexibility and adaptability. The system contains a batch rotary kiln reactor with a processing capacity of 750 kg per batch which is fed with urban plastic waste, to produce pyrolytic oil, syngas and char. The produced pyrolytic oil exhibits an energy content comparable to that of conventional diesel fuel. Additionally, the integration of biomass briquettes and recycled pyrolytic gas can reduce to a big extent the external energy requirements, improving the system’s overall energy autonomy. Therefore, the system becomes economically reliable due to its low operational expenses and the short cycle of approximately 7-h operation. The unit’s mobility enables on-site treatment operations which reduces both transportation emissions and expenses. The analysis includes technical design elements together with performance metrics for different plastics. This conceptual study demonstrates the feasibility of containerized pyrolysis as a practical method to enhance plastic waste chemical recycling rates while presenting a scalable framework for industrial symbiosis and local waste-to-energy conversion. Full article

This study experimentally investigated the movement, combustion, and potassium (K) and chlorine (Cl) migration behaviors of three biomass types: densified wood pellets (heavy), corn straw (lightweight), and wheat straw (lightweight, friable). The experiments were conducted under conditions representative of industrial coal-fired circulating fluidized bed (CFB) boilers, with a temperature range of 850–950 °C and a fluidization velocity of 6–8 m/s. Results show that densified wood pellets sink into the dense-phase zone and release volatiles slowly, in about 50 s. As the volatiles are nearly fully released, the pellets fracture multiple times along their length, eventually forming nearly spherical particles. Their movement and combustion processes closely resemble those of coal, making them suitable for direct co-firing in coal-fired CFB boilers. Conversely, corn straw and wheat straw exhibit low density, high volatile release rates (2 and 10 times that of wood pellets, respectively), rapid char fragmentation and abrasion, and high inherent K and Cl content (with >50% of K and >90% of Cl released). These properties lead to particle segregation, shortened gas-phase combustion time, an upward shift in heat release distribution, and potential risks such as high-temperature KCl corrosion, HCl dew point corrosion, ash slagging, and bed agglomeration. Therefore, untreated corn straw and wheat straw are unsuitable for co-firing in conventional coal-fired CFB boilers. This study provides essential data and engineering guidance: strict quality control is necessary for wood pellets to prevent Cl contamination, while pretreatment is mandatory for straw fuels. These findings offer practical insights for implementing diverse biomass co-firing strategies in coal-fired CFB boilers. Full article

In this study, thermogravimetric analysis was employed to investigate the non-isothermal combustion behavior and kinetic characteristics of poplar biomass under air and oxy-fuel (O₂/CO₂) atmospheres. The effects of heating rate and oxygen concentration on combustion performance, gaseous emissions, and kinetic parameters were systematically analyzed. Results show that poplar biomass combustion consists of four distinct stages: moisture evaporation, devolatilization with volatile oxidation, char and fixed carbon oxidation, and final burnout. Increasing the heating rate intensifies the combustion process, shifting characteristic temperatures to higher values and significantly enhancing the comprehensive combustion index. Compared with air combustion, oxy-fuel conditions reduce ignition temperature and the temperature corresponding to the maximum combustion rate, leading to an earlier ignition and a more concentrated reaction interval. Higher oxygen concentrations further improve overall combustion performance and promote more complete carbon conversion. Gas emission analysis indicates that oxy-fuel combustion effectively suppresses NO₂ and SO₂ formation, demonstrating notable emission-reduction potential. Kinetic analysis using the Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa isoconversional methods shows that the activation energy varies with conversion degree and is generally higher under oxy-fuel atmospheres than in air. Overall, oxy-fuel combustion enhances biomass reactivity while achieving coordinated emission control through increased oxygen partial pressure and improved heat and mass transfer, supporting its practical application in biomass energy systems. Full article

In this study, we developed an eco-friendly intumescent flame-retardant coating for polyester (PET) fabrics. The coating was formulated with aluminum diethylphosphinate-based flame retardant (P-FR), trisilanol isobutyl-POSS (Si-FR), sericin (SC), and poly(vinyl alcohol) (PVA), using citric acid (CA) as a chemical crosslinker. The coatings were applied to alkaline-treated PET fabrics via the knife-coating technique, followed by drying and curing. P-FR acted as the primary flame-retardant component, while SC and Si-FR served as N/Si synergistic agents that enhanced the performance of P-FR, as demonstrated by an improvement in the UL 94 rating from V-1 to V-0. Thermogravimetric analysis indicated that SC and Si-FR improved the oxidative stability of the char. Flame-retardant finishing increased the limiting oxygen index (LOI) from 21.1% for untreated fabric to 31.7% for treated fabric, while tensile strength increased and elongation at break decreased. Notably, after 50 washing cycles, the treated fabrics retained self-extinguishing behavior, although the UL 94 classification decreased to V-2. Overall, this halogen-free coating system effectively enhanced the flame retardancy of PET fabrics while using environmentally friendly components, indicating its potential for sustainable flame-retardant textile applications. 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

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

Polystyrene (PS) is widely used yet highly flammable, and developing halogen-free flame retardants that ensure both high fire safety and mechanical performance remains a challenge. A green intumescent system comprising ammonium dihydrogen phosphate (ADP) and phytic acid–triethylenetetramine (PA–TETA) was incorporated into PS powder via sequential solution grinding and hot pressing. The optimal formulation, PS/10ADP/15PA–TETA, achieved a limiting oxygen index of 28.5% with a UL-94 V-0 rating, and reduced the peak heat release rate and total heat release by 73.8% and 46.2%, respectively, while retaining 78.4% of the tensile strength of neat PS. The ADP/PA–TETA system operates via a cooperative condensed-phase charring and gas-phase dilution mechanism, achieving superior flame retardancy in PS composites. This work provides an effective and eco-friendly strategy for fabricating high-performance PS composites with balanced flame retardancy and mechanical properties. Full article

This study investigates the pyrolysis behavior of loblolly pine through thermogravimetric (TGA) and derivative thermogravimetric (DTG) analysis under varying nitrogen flow rates of 5–40 mL min⁻¹ and heating rates of 5–20 °C min⁻¹. The pyrolysis proceeded through three distinct phases: Phase I: initial moisture release, Phase II: active devolatilization, and Phase III: char formation. Kinetic modeling using both integral and differential forms of the Coats–Redfern method revealed distinct mechanistic interpretations. The integral approach primarily identified diffusion-controlled models (D1, D3) during moisture and char stages and reaction-order or contraction models (F2, R2) during devolatilization, with activation energies ranging from 8.89 to 70.48 kJ mol⁻¹. In contrast, the differential method captured sharper transitions and favored complex nucleation and growth mechanisms (A3, A4) and power laws (P3, P4), yielding higher activation energies up to 111.29 kJ mol⁻¹ in Phase II. These results underscore the influence of both inert gas flow and thermal ramp on pyrolysis reactivity and demonstrate that kinetic model selection significantly affects activation energy interpretation. The findings contribute to a more nuanced understanding of biomass pyrolysis and offer insights into reactor design and process optimization in thermochemical conversion systems. Full article

Plastic waste poses a major environmental issue because it persists in nature for long durations and recycling facilities are not readily available. The conversion of waste materials into hydrogen creates two beneficial effects that help decrease pollution levels and establish hydrogen as a clean energy source for sustainable low-carbon systems. In this study, an integrated process for plastic-to-hydrogen conversion was developed using Aspen HYSYS v14. The system uses pyrolysis, steam reforming, and the water–gas shift (WGS) reaction, through pseudo-components of polyethylene, polypropylene and polystyrene to model decomposition processes. Following optimization, the hydrogen fraction in the syngas rose from 0.664 to 0.733. At this stage, the process produced roughly 651 kg of hydrogen per hour in steady operation. In addition, char and pyrolysis oil were produced as co-products that can be valorized in circular economy applications The implementation of heat integration achieved an 8% reduction in utility demand that proves that internal energy recovery stands as a vital element for sustainable design. The techno-economic analysis showed that the project would achieve a 39% internal rate of return and payback period of 5.95 years, thus proving its financial stability. The research demonstrates how modern process modeling techniques enable the creation of clean technology systems that address plastic pollution problems while producing low-carbon hydrogen. Full article

The growing demand for carbon-based energy materials requires sustainable alternatives to fossil fuels. This study explored the production and characterization of char obtained from refuse-derived fuel (RDF) and biomass blended pellets in varying proportions (0%, 15%, 25%, 50%, and 100% RDF). The objective was to evaluate their potential as high-energy-density solid fuels while addressing operational challenges related to ash behavior. Chars were produced at 400 °C for one hour in a muffle furnace in closed crucibles. A set of analytical techniques (calorimetry, infrared spectroscopy, thermogravimetry, inductively coupled plasma, and X-ray fluorescence) was employed to assess physicochemical properties. RDF content strongly affected mass yield, energy yield, and thermochemical behavior. Among the tested formulations, char with 50 and 25% of RDF (C_RDF50:BW50 and C_RDF25:BW75) ignited at lower temperatures (≈150 °C) and showed high flammability (C) values (1.97–2.03 × 10⁻⁵), indicating greater flammability. They also reached higher combustion temperatures (716–746 °C), suggesting improved thermal stability during the final combustion stage. Both chars presented increased high heating values (18–19 MJ/kg, dry basis) and a few surface functional groups. This supports a lower devolatilization rate, meaning that although ignition is easy, combustion remains stable and controllable. All chars showed very high acid–base indices, indicating a strong tendency for ash melting. However, low slag viscosity and alkalinity values suggest viscous, poorly mobile slag, reducing adhesion and buildup on reactor surfaces. This study combines thermogravimetric combustion analysis with ash chemistry–based slagging and fouling indices to provide an integrated assessment of the operational behavior of RDF–biomass-derived char fuels. The results highlight the technical feasibility of chars produced from RDF and biomass blended pellets, whose thermal properties make them promising candidates for use as solid fuels. Full article