Reduction In Heat Release Rate Research Articles

Comparative analysis of ammonia and hydrogen fuel blends in diesel engines on performance, emission, vibration, and acoustic profiles

In the current study two kinds of gaseous fuels, ammonia and hydrogen tested along with the neat diesel. A series of test conducted in the diesel engine for the samples such as diesel, S1, S2, S3 and S4. The samples were varied based on the two different flow rates 5 LPM and 10 LPM. The parameters such as brake thermal efficiency (BTE), brake specific energy consumption (BSEC), combustion parameters, emissions, and noise levels were determined. The research suggests that the typical properties of ammonia and hydrogen blends contribute to engine performance and efficiency. The S4 blend, 10 LPM of NH3 and 10 LPM of H2, with a higher hydrogen content, was found to significantly enhance BTE across all engine brake powers compared to conventional diesel fuel. A notable increase in BTE with a climb on the brake power was observed, suggesting superior fuel energy utilization due to the blend's high-energy content. An inverse relationship was established between BTE and BSEC, where diesel demonstrated higher BSEC, indicative of greater thermal loss and inefficiency. Combustion analysis revealed a reduction in heat release rate for ammonia blends, this eventually compensated by hydrogen addition by optimizing autoignition and accelerating combustion. Emission studies highlighted a uniform increase in nitrogen oxides for all blends; however, the combination of hydrogen with ammonia was shown to mitigate NOx formation by lowering flame temperatures. Additionally, vibrational analysis demonstrated that ammonia and hydrogen blends reduce engine vibration, especially at higher loads, and contribute to decreased combustion and exhaust noise.

Improving flame retardancy in BADGE epoxy via novel phosphorus‐functionalized epoxy integration

AbstractA novel epoxy resin, DPHP, was synthesized from diphenolic acid, which contains biobased levulinic acid, with triethylphosphite, to improve the flame retardancy of bisphenol‐A diglycidyl ether (BADGE) epoxy. Curing experiments were conducted using isophorone diamine as a curing agent for BADGE and DPHP mixtures. Variations in cure kinetics, mechanical properties, and flame retardancy were evaluated across different DPHP contents. The introduction of phosphorus functional groups into DPHP affected the polarization of epoxide CO bonds, resulting in reduced apparent activation energy for epoxy curing reactions. However, the higher epoxy equivalent weight of DPHP compared with that of BADGE led to a decrease in the tensile strength and the glass transition temperature of the cured material with increasing DPHP content. A significant increase in char yield for combustion of the epoxy blend was observed, ranging from 8.3% at 0 wt% DPHP to 20.1% at 50 wt% DPHP. Additionally, cone calorimeter measurements showed significant reductions in heat release rate and total heat release, leading to a decrease in fire spread from 1.07 MJm−2 s−1 at 0 wt% DPHP to 0.43 MJm−2 s−1 at 50 wt% DPHP. These results show that the flame retardancy of the cured material improved significantly as the DPHP content increased.

Optical diagnostics in impact of ammonia energy ratio and diesel split ratio on combustion process and flame propagation in an Ammonia-Diesel Dual-Fuel engine

In the context of ammonia-diesel dual-fuel (ADDF) engines, challenges such as ignition difficulties and misfires emerge prominently at elevated ammonia energy ratios. To alleviate these challenges, this study aims to elucidate the effects of ammonia energy ratios (AER) and diesel split ratios (DSR) on the combustion process and flame propagation in an optical ADDF engine configuration. Utilizing optical diagnostics, including flame luminescence and high-speed photography, the study provided insights into combustion boundary conditions specific to ADDF engine operation. The results highlight that an increase in AER to 60 % results in a marked decrease in peak cylinder pressure, peak apparent heat release rate (AHRR), and the in-cylinder pressure rise rate. This is accompanied by a reduction in IMEP from 4.16 bar to 3.24 bar, indicating a decline in combustion efficiency upon greater ammonia addition. Flame luminosity exhibits a shift from a diesel-like blue hue to an ammonia-tinted pale yellow. This change coincides with a significant reduction in soot formation and restrictions in flame area and propagation speed, largely due to ammonia's intrinsically slower burning velocity and its chemical interplay with diesel. Implementing a dual injection approach further accentuates the peak in-cylinder pressure and AHRR, with the second injection playing a crucial role in ignition. Optimizing the DSR to 40 % improves combustion efficiency, attributed to enhanced fuel-oxygen interactions. Conversely, DSR values of 60 % and 80 % pose challenges. A reduction in diesel content in the subsequent injection leads to a leaner blend, subsequently affecting combustion efficiency, as indicated by reduced heat release rate and diminished IMEP. This study emphasizes understanding the ammonia-diesel interaction and the importance of choosing the appropriate DSR to exploit the advantages of ADDF engines.

A Low‐Temperature Carbonization Strategy for Efficient Viscous Crude Oil Spill Disposal without Hydrophobic Coating: CoFe‐PBA‐Catalyzed Carbonization of Superhydrophobic Flame Retardant Melamine Sponge

AbstractDue to the difficulty of absorbing viscous crude oil, there is an urgent need for carbon sponges with excellent photothermal properties and oil‐water separation capabilities to reduce viscosity and facilitate oil absorption. However, the preparation of high‐temperature carbonization leads to poor mechanical properties, low absorption capacity, and stringent preparation conditions. To solve these challenges, a highly hydrophobic flame‐retardant melamine sponge (CPBA@CMS) is designed by assembling sponge at the interface of cobalt–iron Prussian blue (CoFe‐PBA) derived from metal–organic frameworks (MOFs) and conducting low‐temperature catalytic carbonization under nitrogen. The results demonstrate that CPBA@CMS exhibits excellent superhydrophobic properties (water contact angle = 169.7°) and oil absorption capacity (80.7–219.5 g g−1). Furthermore, CPBA@CMS displays remarkable photothermal effects and thermal conductivity, making it adaptable to various environmental conditions. It can rapidly rise to 141 °C under 1 kW m−2 solar irradiation, with the maximum oil absorption rate reaching 98% and the highest oil absorption capacity at 105.5 g g−1. Additionally, CPBA@CMS shows significant fire safety performance, reducing heat release rate by 84.2%, smoke factor by 97.5%, and CO release rate by 81.4%, respectively. It provides an efficient, safe, and sustainable practical solution for effectively addressing spills of crude oil.

Fire performance, toxicity, and thermal diffusivity of wastepaper mixed with magnesium hydroxide, depending on the particle size of expandable graphite

As the construction of high-rise buildings increases to solve residential spaces caused by high density population concentration, the occurrence of fire accidents in high-rise buildings is also increasing. The primary cause of fire damage in high-rise buildings is the spread of fire caused by exterior wall finishes. Therefore, it is essential to develop semi-non-combustible finishes that can be applied to high-rise buildings to prevent the spread of fire due to exterior wall finishes. To address this issue, numerous studies are being conducted to develop flame retardant finishing materials that reduce heat release rate and total heat release. A double flame retardant mixed waste paper with expandable graphite and magnesium hydroxide was manufactured to improve the fire performance of cellulose building finishing materials. Total heat release (THR), CO, and CO2 Generation changes were measured using a cone calorimeter, and thermal diffusion rate was measured through the LFA 1000 experiment. The correlation of total heat release, CO generation, CO2 generation, and mass reduction rate by variation of expandable graphite's mesh size at double flame-retardant waste paper were secured through a cone calorimeter test. The thermal diffusion rate data of the specimen were secured through the LFA 1000 experiment. Through experiments, it has been confirmed that specimens using specific expandable graphite particles can be utilized as fire-resistant finishing materials in construction, ensuring fire resistance performance.

Improvement of heat release methodologies using mass loss calorimeter and oxygen consumption hood to assess flammability of wood plastic composites

The mass loss calorimeter provides a robust method for evaluating flammability of very sooty materials such as wood plastic composites as a lower cost and rugged alternative to the reliable and effective cone calorimeter. The high amounts of smoke and carbon monoxide associated with these materials resulted in a much-reduced heat release rate, resulting in incomplete combustion of the diffusion flame, which required modifications to the standards in measuring heat release rate via oxygen consumption or carbon dioxide production or thermopiles. In addition to liquid fuels of ethylene glycol and methanol, the solids polystyrene and polymethyl methacrylate were used as calibration materials for the mass loss calorimeter and the instrumented heat release rate hood. Because of concerns about the flue gas thermopile methodology for heat release rate measurements, a second thermopile was attached to the exterior of the metal pipe chimney typically used for heat release rate calculations in the mass loss calorimeter. A heat balance analysis indicated that this is an effective design compared with alternative designs. Estimates of flaming heat release rate are reported using both signals from the thermopiles for calculation of heat release rates and confirmed with the updated oxygen consumption analysis under an instrumented hood. This special fire test arrangement was used to assess the flammability of four different wood plastic composites, some with fire-retardant treatments, such as ammonium polyphosphate and brominated, all of which tended to have high smoke production leading to high-radiant energy losses. The reduction of heat release rate with 10% by content of fire-retardant treatment was confirmed by both heat release rate measures. The average heat release rate decreased 19% to 39% when fire retardants were added, relative to this wood flour–polyethylene composite.

Hexaphenoxy cyclotriphosphazene/boron nitride high-efficiency charring system enhancing the flame retardancy and thermal conductivity of polycarbonate

Polycarbonate (PC), as an engineering plastic, has excellent mechanical properties and electrical insulation properties. Nevertheless, with the rapid spread of 5 G applications, there is an increasing demand for functional PC materials with both thermal conductivity and flame retardant properties. In this study, the flame retardant thermal conductivity composite system of boron nitride (BN) and hexaphenoxy cyclotriphosphazene (HPCP) was constructed to study the simultaneous improvement of the flame retardant and thermal conductivity of PC. The results reveal that the inclusion of HPCP and BN in PC can significantly enhance its flame retardancy. This enhancement is evidenced by prolonged ignition time, reduced heat release rate and decreased total smoke production. In particular, 20BN/3HPCP/PC composite shows the best flame retardant effect. Through the investigation of flame retardant mechanisms, it has been found that the network structure formed by the BN sheets with phosphorus-containing products of HPCP decomposition can effectively filter and adsorb pyrolysis debris and increase the residence time of burning fragments in the pyrolysis zone promoting the pyrolysis products further fully burned to reduce the smoke caused by incomplete combustion. The phosphoric acid substances after the decomposing of HPCP can promote PC matrix to dehydration and carbonization to form the phosphorus-containing residues, which adheres on the BN network structure to form hardness char layers in the condensed phase to play an excellent role in blocking heat and combustible flue gas, which has a positive effect on reducing heat release rate and improving flame suppression. In terms of improving thermal conductivity, the infrared thermal imaging experiment further confirmed that BN sheets can increase the thermal conductivity of PC composites by more than 4 times, and the layer and layer stacks structure of BN sheets can endow an efficient thermal conductivity path for PC matrix to improve the thermal conductivity. Therefore, this study is meaningful practical exploration for developing the PC composites with excellent thermal conductivity and flame retardancy.

Effect of nanoparticles (Al2O3 and CeO2) blended with biodiesel on combustion, performance, and emissions of a diesel engine

The increase in the utilization of fossil fuels in almost all the energy production sector badly impacts the environment because of incomplete combustion. The incomplete combustion of fuels releases soot, unburned hydrocarbon, and greenhouse gas emissions, contributing significantly to climate change. In the current experimental work, the evaluation of the effect of the addition of aluminium oxide (Al2O3) and cerium oxide (CeO2) nanoparticles in Jatropha biodiesel (B20) has been performed on the combustion, performance, and emission characteristics of compression ignition engine. These nanoparticles have been added because they have a large surface area-to-volume ratio. The air-fuel mixture and the evaporation rate are enhanced, leading to improved burning. The increase in brake thermal efficiency has been observed with nanoparticles blended fuel, i.e. (B20 + 30 ppm Al2O3 + 30 ppm CeO2) by 9.354%. In contrast, drop-in oxides of nitrogen, carbon monoxide, HC, and smoke opacity emissions were observed by 24.67%, 33.33%, 23.08%, and 34.01%, respectively, compared with pure biodiesel. Using nanoparticles in Jatropha methyl ester reduces ignition delay, increases combustion duration, and starts earlier combustion, reducing heat release rate, cylinder pressure, and pressure rise rate by 10.53, 1.994, and 3.687%, respectively, as compared to the B20 blend.

Improvement of thermal stability and flame retardancy of beech wood fibers using steam explosion and phosphorylation reaction

An environmentally friendly approach was studied for improving the fire retardancy of beech wood using a steam explosion process coupled with a phosphorylation reaction. Raw beech, steam-exploded, or bleached wood was subjected to phosphorylation employing etidronic acid (HEDP) and urea, and the resulting chemical composition and thermal behavior were analyzed using techniques such as elemental analysis, Fourier transform infrared spectroscopy, ionic chromatography, and pyrolysis combustion flow calorimetry. The thermal performance of beech wood underwent significant enhancements after the steam explosion treatment combined with soda impregnation. It resulted in a striking reduction in heat release rates (HRR), especially its peak (pHRR) and time-to-pHRR (TpHRR) values (from 139.5 W/g and 365 °C to 40 W/g and 247 °C) and an increase in residue from 10.5% to 41.3%. The results demonstrate that the process created a self-extinguishing and non-flammable material that exhibited noteworthy flame retardancy improvement.

Hydrophobicity, transparency, mechanically excellent and fire safety multifunctional epoxy resin based on a novel DOPO derivative with cyano group

A novel derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) bearing cyano groups, referred to as PDPO, was successfully synthesized and applied as an additive for epoxy resin (E-44, with epoxide equivalent weights ranging from 201 to 240 g/epoxide), along with the curing agent 4,4′-diaminodiphenylmethane (DDM). Comprehensive characterization techniques, including Fourier transform infrared (FTIR) spectroscopy, 1H and 31P nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis (EA), were employed to confirm the chemical structure of PDPO. Thermogravimetric analysis (TGA) revealed remarkable thermal stability for PDPO, with a substantial char residue of 43.1 wt% at 800 °C. Introducing 5 wt% PDPO into the EP formulation resulted in a notable enhancement of fire retardancy, as evident from the increased Limiting Oxygen Index (LOI) value of 32.2 % and the attainment of UL-94 V-0 rating for the EP/PDPO-5. The efficacy of fire retardancy was further underscored by cone calorimeter (CC) testing, which showcased a reduction in heat release rate and smoke production. An in-depth analysis of pyrolysis behavior and char formation demonstrated that PDPO exhibited multifaceted roles in both the gas and condensed phases, contributing to the fire retardant properties of the material. Additionally, the incorporation of PDPO at a concentration of 1 wt% led to notable enhancements in the tensile and flexural strength of EP/PDPO-1 by 15.2 % and 10.4 %, respectively, compared to neat EP. Remarkably, the transparency of EP/PDPO-1 was preserved at 95.6 %, while the water contact angle was elevated to 115.5°, indicating improved hydrophobicity. These results collectively highlight the potential of PDPO as a fire-retardant additive, demonstrating its ability to simultaneously stay transparency and enhance mechanical properties and hydrophobic characteristics in the EP/PDPO systems.

Effect of Plasma-Enhanced Low-Temperature Chemistry on Deflagration-to-Detonation Transition in a Microchannel

This study examines low-temperature chemistry (LTC) enhancement by nanosecond dielectric barrier discharge (ns-DBD) plasma on a dimethyl ether (DME)/oxygen (Ar) premixture for deflagration-to-detonation transition (DDT) in a microchannel. It is found that non-equilibrium plasma generates active species and kinetically accelerates LTC of DME and DDT. In situ laser diagnostics and computational modeling examine the influence of the ns-DBDs on the LTC of DME and DDT using formaldehyde () laser-induced fluorescence (LIF) and high-speed imaging. Firstly, high-speed imaging in combination with LIF is used to trace the presence of LTC throughout the flame front propagation and DDT. Then, competition between plasma-enhanced LTC of ignition and reduced heat release rate of combustion due to plasma-assisted partial fuel oxidation is studied with LIF. Observations of plasma-enhanced LTC effects on DDT are interpreted with the aid of detailed kinetic simulations. The results show that an appropriate number of ns-DBDs enhances LTC of DME and increases formation and low-temperature ignition, accelerating DDT. Moreover, it is found that, with many ns-DBDs, concentration decreases, indicating that excessive discharges may accelerate fuel oxidation in the premixture, reducing heat release and weakening shock–ignition coupling, inhibiting DDT.

Coating Composites Based on Polyurea Elastomers with Increased Fire Resistance and Their Use as Roofing Systems

This paper presents the results of tests on elastomer coatings based on polyurea–polyurethane formulation with increased fire parameters. Coatings modified with flame retardants: bis(phenylphosphate) resorcinol (RDP), trischloropropyl phosphate (TCPP), and aluminum hydroxide (ATH) were tested. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA/DTG) were used to investigate the structure and thermal stability. The effectiveness of resorcinol bis(phenylphosphate) (RDP), tris chloropropyl phosphate (TCPP), and aluminum hydroxide (ATH) on heat release rate (HRR), smoke release rate (RSR), and oxygen consumption was evaluated using cone calorimetry. The cone calorimetry results were correlated with the mechanical properties of the coatings. The cone calorimetry analysis showed suitable organophosphorus flame retardant (FR) performance, significantly decreasing HRR and oxygen consumption. Additionally, 15% TCPP caused a reduction of HRR by over 50%, obtaining 211.4 kW/m2 and pHRR by over 55%, reaching 538.3 kW/m2. However, organophosphorus flame retardants caused a significant deterioration of mechanical properties simultaneously. Introducing a mixture of two FRs (RDP/TCPP) resulted in obtaining a coating with improved fire resistance and maintained good mechanical strength. The polyurea–polyurethane coating, modified with a mixture of two RDP/TCPP retardants (10:5), was simulated for the burning of roof systems. The result of the simulation was assessed positively. Thus, finally, it was confirmed that the proposed polyurea–polyurethane coating achieved the assumed flame retardant level.

Facile preparation of inherently flame-retardant polyamide 6 filaments with enhanced anti-dripping enabled by the synergistic charring effect

The absence of inherently flame-retardant polyamide 6 (FR-PA6) with enhanced anti-dripping and melt spinnability has significantly limited its further application in textiles. In this work, a binary reactive flame retardant composed of commercial 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phosphaphenanthrene-10-oxide (DDP) and synthesized polydiphenylsiloxane (PDPS) was employed to fabricate FR-PA6 through a facile synthetic route. The prepared FR-PA6 containing 5 wt% DDP and 5 wt% PDPS (FR-PA6-5-5) exhibited a UL94 V-0 rating with no melt-droplets during combustion, a 31.0% reduction in heat release rate and a 18.8% decrease in total heat release compared to pure PA6 in cone calorimetric tests. The improved fire safety of FR-PA6-5-5 was contributed to the gas-phase quenching and dilution effect and the condensed-phase barrier effect, which was enhanced by the synergistic charring effect achieved through the formation of P(=O)-O-Si. Additionally, FR-PA6-5-5 exhibited excellent melt spinnability as demonstrated by the successful preparation of filaments with a tensile strength of approximately 2.27 cN/dtex.

Phytic Acid-Silica System for Imparting Fire Retardancy in Wood Composites

Fire-retardant (FR) treated wood-based panels, used commonly in furniture and construction, need to meet stringent fire safety regulations. This study presents a novel treatment for imparting fire resistance to wood composites by applying separate solutions of phytic acid and sodium silicate onto wood particles before the hot pressing at 160 °C. A scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) analysis revealed that phytic acid and sodium silicate were uniformly distributed throughout the wood particles, and the formation of silica gel resulted in the aggregation of elemental silicon. Fourier-transform infrared spectroscopy (FTIR) displayed that phytic acid caused the thermal degradation of hemicelluloses, which led to a brownish outer appearance of the FR-treated composites. Fire performance was assessed using both limiting oxygen index (LOI) and a cone calorimeter. These techniques showed a higher LOI value and a significant reduction in heat-release rate (HRR), total heat release (THR), smoke-production rate (SPR), and total smoke production (TSP). In addition, cone calorimeter and thermogravimetric (TGA) analyses consistently showed increased char residue in treated wood composites. Moreover, internal bond strength (IB) and modulus of elasticity (MOE) of the wood composite were not significantly changed compared with those of the untreated composite. Surprisingly, in the FR-treated composite, the 24 h-thickness swelling, and the water uptake were slightly decreased. Consequently, this new treatment has the potential to increase the fire retardancy of wood composites, such as particleboard, without deteriorating the key mechanical properties.

The effect of hybridization of fire retarded epoxy/flax-cotton fiber laminates by expanded vermiculite: Structure-property relationship study

The study describes the hybridization of epoxy/flax-cotton (EP/FF) composites containing ammonium polyphosphate (APP) with micrometric expanded vermiculite (VMT) (1–10 wt%). The efficiency of hybridization of flame retarded epoxy/flax-cotton composites was assessed by performing static tensile and flexural strength evaluation, supplemented by impact strength measurements of the composites. Moreover, thermal and thermomechanical analyses (DMA, DSC, and TGA) were performed. Epoxy composites were subjected to flammability using a PCFC microcalorimeter and cone calorimeter measurement to assess the burning behavior of composites. The introduction of the low-cost plate-shaped filler resulted in several favorable thermal effects while deteriorating the structure of the composite. The addition of small amounts of vermiculite (1–2 wt%) into the matrix modified with APP enabled the reduction of heat release rate (HRR) and total heat release (THR) by 60% and 20%, respectively. The comprehensive structure-properties analysis determined the critical filler contents, yielding synergistic flame-retardant effects with a limited negative impact on the composites' performance.

Expanding Chitosan Reticular Chemistry Using Multifunctional and Thermally Stable Phosphorus-Containing Dendrimers

Chitosan is an astonishing building block that is extracted from marine crustacean waste, features randomly distributed amino and acetamido groups in its backbone, and can be handled in different forms, giving rise to an impressive diversity of functional nanomaterials. Hitherto, its reticular chemistry, although mandatory to circumvent its main drawback of instability, has been dominated by the use of glutaraldehyde. Unfortunately, the toxicity and inherent chemistry of the latter narrow further development of such cross-linked materials and constitute an impediment for their massive spreading and real implementation, especially in nanomedicine and related healthcare applications. Prompted by the well-established advantages of dendrimers, more distinctively those containing phosphorus in their skeleton, we herein explore the use of second- and third-generation phosphorus-containing dendrimers as cross-linkers to provide an extended covalent dendritic framework grown inside of the carbohydrate network. The presence of residual amine and aldehyde defects was explored to conjugate other chemicals (viologen-based ionic liquid and aminopropyltriethoxysilane) thereby adding more functional diversity to the assembled framework. We also leveraged on the film-forming ability of chitosan to shape the reticular network as flexible films. Despite the bulkiness of the used phosphorus dendrimers, the film-forming memory of chitosan was preserved, allowing successful preparation of highly functional, transparent, and flexible micrometer-thick bioplastics. The cross-linking seems to delay the half-weight degradation temperature of the plastics, with a significant increase in the char residue and a reduced heat release rate. Ternary objects (Congo red dye and gold nanoparticles) could also be entrapped within the transparent films without leaching or degradation, thereby expanding the usefulness of these transparent coatings as multifunctional sensors, flame retardants, biofoulants, etc.

New Polymer Composites with Aluminum Phosphates as Hybrid Flame Retardants.

Polymeric aluminum organophosphates are a class of nanostructured aluminum-based compounds that can be considered organic and inorganic hybrid materials. Aluminum phosphates have attracted considerable interest due to their ability to enhance composite materials' mechanical characteristics, lightweight, and thermal properties. Extensive studies have shown the potential of aluminum organophosphates as a component in the development of fire-retardant materials. Aluminum-organophosphorus hybrid (APH) materials have been prepared by reacting aluminum oxide hydroxide (boehmite) with alkyl and aryl phosphoric acids and used to prepare composites with epoxy resin. Boehmite is an aluminum oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminum ore bauxite. In this work, the composites based on epoxy resin Epidian 601 and commercial curing agent IDA were obtained. Pure boehmite and APH hybrids were added as flame retardants. FTIR and TGA analysis showed that obtained APH possesses a hybrid structure, high thermostability, and various morphologies. These new APH were incorporated into epoxy resin. The infrared spectroscopy confirmed the structure of hybrids and composites. Pyrolysis combustion flow calorimetry (PCFC) and cone calorimeter analyses were performed to assess the flame retardant properties of the composites. The results showed that the incorporation of 17 wt% APH allows a reduction of heat release rate but to a limited extent in comparison to pure boehmite, which is due to the different decomposition mechanisms of both boehmite and hybrids. The cone calorimetry test showed that residue contents correspond quite well to the mineral fraction from boehmite only. The hybrid APHs appear no more efficient than pure boehmite because the mineral fraction in APH is reduced while phosphate fraction cannot promote significant charring.

Synergistic effects of molybdenum disulfide on a novel intumescent flame retardant polyformaldehyde system

AbstractA novel intumescent flame retardant (IFR) composed of ammonium polyphosphate (APP), benzoxazine containing trialkoxysilane (BA‐a‐Si) and melamine (ME), is compounded with different specifications of MoS2 as synergist to flame retard polyformaldehyde (POM). The flame retardancy and mechanism of the composites are analyzed by limiting oxygen index (LOI), vertical combustion (UL‐94) and cone calorimeter. At the same time, the mechanical properties and lubricating properties are tested by electromechanical testing machine and wear testing machine. The experimental results show that MoS2 has a good synergistic effect with IFR, and the smaller the average particle size of MoS2 is, it seems to be more beneficial to improve the flame retardancy of POM composites. Only a small amount of MoS2 (0.8 wt%) is needed to synergize with IFR, the flame retardant POM composite (FR‐POM) can achieve UL‐94 (3.2 mm) V‐0 rating, LOI of 62.5%, and heat release rate reduction of 25.3%, total smoke release decreased by 29.5%. In addition, from the mechanical properties analysis, it is found that the microscale MoS2(M2) can better improve the bending and tensile properties of the FR‐POM composites, while the nanoscale MoS2(N80) is more helpful to improve the lubricating properties.

Bioinspired multilayer multiscale architectures into PDMS for simultaneously enhancing the thermal conductivity and flame retardancy

Combing high thermal conductivity and excellent flame retardancy is crucial for the development of thermal management composites. Herein, we report a bioinspired multilayer multiscale architecture comprising nanoscale MXene as the protective layer 1, atomic Cu2+ coordination molecular scale dendritic PEI as the protective layer 2 and encapsulated flammable PDMS as a matrix. Upon exposure to flame, the two layers can hinder polymer combustion, wherein MXene nanosheets and PEI-Cu serve as a barrier and thermally conductive layers, as well as catalytic and adsorption layers, respectively. As a result, the as-prepared PDMS composites exhibit a high out-of-plane thermal conductivity of ∼0.60 W m−1k−1, a reduced heat release rate and extremely low smoke (CO and CO2) generation at low filler loadings, suggesting excellent smoke suppression and toxicity reduction. This study provides a new strategy for the development of polymer composites with high thermal management capabilities and excellent flame retardancy.

Restricted assembly of ultralow loading of graphene oxide for lightweight, mechanically flexible and flame retardant polydimethylsiloxane foam composites

Lightweight, mechanically flexible and flame retardant polydimethylsiloxane (PDMS) foam materials modified with low content of nano-fillers are highly needed for versatile applications. Instead of the direct mechanical mixing technique that induced the embedment of nanofillers inside the matrix, herein, a facile, rapid and green restricted assembly strategy was established to prepare PDMS foam composites coated with an extremely low content of restricted graphene oxide (GO) sheets. A GO/water mixture in silicone oil emulsion was prepared to produce the restricted assembly of GO layers precisely and solely on the foam surface with no GO sheets inside the skeleton. Based on such restricted assembly induced by the amphiphilic surfactant molecules, the presence of only ∼0.04 wt% GO greatly improved the flame resistance (e.g., 40.6% reduction in heat release rate and 27.1% of limit oxygen index) of PDMS foams without affecting the low density (∼0.23 g/cm3) and mechanical flexibility (unchanged stress at strain 70% after 100 cycles under 200 °C). Observations and analysis of the burnt zones demonstrated that the restricted ultralow content GO sheets formed a compact protective layer facilitated by the pyrolysis of the PDMS molecules, thus protecting the inside of the PDMS material from the heat and oxygen attacks. These results confirmed that the restricted self-assembly of 2D nano-fillers approach is effective for the fabrication of flame-retardant PDMS foams and retention of other important properties.