Flammability Characteristics Research Articles

Effect of Silicon-Based Surfactant on Compression Strength, Morphology, and Flammability of the Aluminium Hydroxide-Filled Rigid Polyurethane Foam

This study investigates the impact of NiaxTM Silicone L-5440, a silicon-based surfactant, on the foaming behaviors of rigid polyurethane foam (RPUF) filled with aluminium hydroxide (ATH). The aim is to understand the effect of the surfactant on the compression strength, morphology, and flammability of the foam. Various concentrations of the surfactant, ranging from 0.5 to 3 pphp, were incorporated into the RPUF/ATH blend. Five key parameters were examined, including density, closed-cell content, structural characterization using scanning electron microscopy (SEM), compressive strength, and UL-94 rating. The results revealed that adding the silicon surfactant significantly influenced the foam properties. Foam formulations with lower surfactant concentrations resulted in denser foam with a higher percentage of closed cells (86.24%). The morphology of the foams exhibited variation in average pore sizes, initially decreasing and subsequently increasing with increasing surfactant concentration. Notably, the compressive strength of the foam increased when the surfactant concentration reached 1 pphp. Moreover, the inclusion of the surfactant improved the flammability characteristics, as evidenced by a UL-94 rating of V-1 without dripping.

Using flammable gas characteristics to evaluate spontaneous flame instability in gas explosions

Using flammable gas characteristics to evaluate spontaneous flame instability in gas explosions

Effect of Flame Retardant R134a on the Flammability Characteristics of R1234yf

The potential alternative 2,3,3,3-tetrafluoropropene (R1234yf) has excellent environmental property but carries a risk of combustion. Therefore, 1,1,1,2-tetrafluoroethane (R134a) was chosen as the matching flame retardant. In this research, the oxidation process of R134a/R1234yf was studied by synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). the oxidation products were identified for the first time, which included CO, CO2, H2O, C2H2, CH2F2 and CH2O. Then, a new kinetic model for the inhibition of R134a on R1234yf combustion was built, which well reproduced the experimental results. The inhibitory effect of R134a on the flammability of R1234yf was evidenced from the microscopic (the molar distributions of typical species and reactions) and macroscopic (adiabatic combustion temperature and laminar burning velocity) properties between pure R1234yf and R134a/R1234yf mixture. The comparative Rates of Production (ROP) analysis for key species (H2O, CO2, C2H2 and CH2F2) and radicals (H, O, OH and F), alongside sensitivity analysis were performed, which elucidated the underlying microscopic mechanism in the flame retarding process. The results also showed that the laminar burning velocity and adiabatic temperature of pure R1234yf were larger than R134a/R1234yf mixture. This paper can provide a new research idea for the safe application of environmentally friendly refrigerants.

Experimental Research on the Ignition Characteristics and Inhibition Strategy for Venting Emissions Mixture of Failure LiFePO4 Battery

When the concentration of a gas is below its lower flammable limit and the content of a liquid is below its minimum explosible concentration, their combined fuel mixture can be ignitable. The flammability characteristics and inhibition strategies for battery emission mixtures deserve further in-depth research attention. This article presents experimental research on the ignition characteristics and inhibition strategy for a venting emission mixture of a failure LiFePO4 battery. By identifying the components of venting emissions, ignition experiments for gases, electrolyte mist, their combination fuels, and mixtures with additives are performed to determine the flammable parameters, including ignition sensitivity and severity. The hybrid combination of non-flammable venting gases and electrolyte mist has the potential to induce ignition. However, there still exists a non-ignition region, where the gas concentration ratio (mg) is below 0.15 and the liquid concentration ratio (ml) is below 0.1. A safety design principle can be proposed: increasing ignition temperature, prolonging ignition time, and reducing maximum pressure. Adhering to this principle, a non-flammable electrolyte consisting of 1 mol LiPF6 in EC:DEC = 1:1 vol%, with FEC at 10% and VC at 1%, can be considered as an optimization strategy. In comparison to the original gas–liquid mixtures, the region where no ignition occurs becomes wider when both the mg is below 0.45 and the ml is below 0.3. The new two-phase mixture has an ignition temperature of 835 °C, which is, respectively, 50% higher than that of the original mixture. Overall, this experimental research demonstrates an innovative methodology for assessing the battery venting emission mixture safety while proposing a design principle for modifying non-flammable electrolyte functional materials. Consequently, these findings can contribute to formulating more suitable preventive and protective measures for commercial electric vehicles and battery energy storage systems’ thermal safety designs.

Emission of Fire-Promoting Volatiles from Picea omorika (Pančić) Purk Needles in Different Forest Communities

The importance of studying the role of volatiles in flammability is well recognized, but the relationship between specific compounds and components of flammability is underestimated. In this study, volatiles emitted from Picea omorika (Pančić) Purk. Needles were identified and quantified, and the relationship between volatile emission and moisture content, flammability characteristics and bioclimatic coefficients was investigated. Fresh needles from four different forest communities were analyzed for specific volatile organic compounds (using a gas chromatography-surface acoustic wave analyzer, GC-SAW), moisture content (based on fresh and oven-dried mass), and flammability components (using an epiradiator). Five monoterpenes, one sesquiterpene, and one alcohol were identified and their amounts, moisture content, and flammability components differed between the populations. The amounts of myrcene and β-pinene correlated significantly with moisture content and time to ignition. Myrcene content also correlated with flame duration, site altitude, mean annual temperature, variation in mean annual temperature, and the Ellenberg quotient. The emission of myrcene correlates with ecophysiological, flammability, topographic, and climatic variables. This suggests that myrcene-rich plant species may be of particular interest for research into flammability, especially from the point of view of rapid ignition.

Controlled Sensor Derived from COF Materials for the Effective Detection of N-Methylpyrrolidone.

N-methylpyrrolidone (NMP) is an excellent advanced solvent that can be easily absorbed by the human body and has the characteristics of flammability and explosion. To reduce the risk, the environmental concentrations of NMP need to be measured. A series of covalent organic frameworks (COF) connected by an imine bond have been successfully prepared at room temperature by changing the synthesis time catalyzed by scandium(III) trifluoromethanesulfonate (Sc(OTf)3). The effect of the synthesis time on the sample properties was compared by XRD, FT-IR, XPS, SEM, TEM, and BET. The results showed that synthesis time had almost no effect on the morphology, specific surface area, and functional groups of the COF samples but had a significant impact on the pore size distribution, residual bonds, and other defects, which in turn affected the gas sensing performance. The sensor results showed that all samples had good sensing performance for NMP, among which the sample synthesized for 48 h had the best sensing performance, with a limit of detection of 692 ppb and good stability and repeatability. The excellent performance of the COF samples benefits from the large specific surface area, hydrogen bonding interactions, electrostatic attraction, and high defects. This study provides an effective method for NMP detection and expands the application range of the COF materials.

Study of quaternary hydrogen and biogas mixtures: An industrial safety approach

Hydrogen and biogas mixtures offer a promising solution to meet industrial heat demands that renewable electricity cannot fully supply. This study investigates the flammability characteristics of quaternary gas mixtures composed of methane (CH4), hydrogen (H2), carbon dioxide (CO2), and air, which are relevant for industrial safety in explosive atmospheres. A novel three-dimensional “flammability tetrahedron” is introduced to represent the flammable regions, limiting oxygen concentration (LOC), and ignition boundaries of these mixtures. Using the Spark Test Apparatus (STA), we experimentally determined the flammability limits for three biogas compositions (BG50, BG60, BG70) blended with varying hydrogen percentages (10–50%). The results demonstrate that hydrogen addition significantly alters the flammability limits and LOC, reducing the required inert gas for safety and extending the flammable range in hydrogen-enriched mixtures. The proposed flammability tetrahedron serves as an innovative tool for the real-time evaluation of gas mixtures, addressing gaps in current safety protocols. This research has substantial industrial applications, particularly in sectors handling methane-hydrogen mixtures, enabling safer operations under the European Union’s ATEX Directives. The findings provide critical insights into explosion prevention and leak detection in industrial processes, supporting the safe integration of hydrogen-enriched biogas into energy systems.

Research on evaluation technology for fuel tank inerting system based on task profile

Abstract The flammable and explosive characteristics of aviation fuel have always made the safety of aircraft fuel tanks a focus of attention in the aviation industry. At present, all aircraft test flights in our country require the completion of the evaluation of the fuel tank inerting subsystem, which has put forward clear requirements for the measurement of oxygen concentration in aircraft fuel tanks, and corresponding technical indicators have been developed based on the usage of civil and military aircraft. This article establishes a digital model of the aircraft fuel tank inerting system based on AMEsim software, verifies the accuracy of the model through literature data, and uses the digital model to study the variation law of oxygen concentration in the fuel tank. The temporal variation of oxygen concentration in the gas-phase space of aircraft fuel tanks is analyzed under different nitrogen-rich gas concentrations, nitrogen-rich gas flow rates, fuel tank loading rates, and aircraft descent rates. Based on the temporal variation of oxygen concentration, a reference is provided for formulating flight test methods.

Constructing a multifunctional reactive MXene-based additive for micro-crosslinking polyurea elastomer to achieve superior mechanical properties and enhanced fire safety

The widespread application of polyurea (PUA) in protective coatings typically requires excellent flame retardancy due to real-world usage scenarios. However, the addition of flame retardant additives often compromises the material’s mechanical properties. In this study, a multifunctional reactive additive, MX-SP-NH2, was creatively prepared by covalently grafting spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) onto MXene (Ti3C2Tx) surfaces, followed by the introduction of 1,3-propanediamine (PDA) by the reaction with SPDPC. MX-SP-NH2 was then incorporated into PUA, participating in its crosslinking process and significantly enhancing both its mechanical strength and flame retardancy. Compared to the control PUA sample, the micro-crosslinked PUA sample with just 1.0 wt% MX-SP-NH2 demonstrated a 184.3% increase in tensile strength, a 126.1% increase in elongation at break, and a 436.3% increase in toughness. The flammability characterization revealed that the peak heat release rate, peak smoke production rate, and peak CO production rate were reduced by 31.7%, 28.9%, and 61.5%, respectively, indicating a substantial improvement in fire safety. Additionally, the flame retardant PUA-based flexible strain sensors demonstrated stable electrical signal responsiveness. This work has opened up new potential applications of PUA in flexible electronics.

Revealing the flame inhibition effect of phytic acid (PA) by PIV measurements and detailed chemical kinetic modeling of counterflow CH4/PA/air flames

As industrialization continues to deepen, polymers have become ubiquitous in daily life. However, their flammable characteristics pose significant safety risks. Therefore, supporting the global goal of sustainable development necessitates the development of high-performance, environmentally friendly flame retardants. Biomass phytic acid (PA) has emerged as a promising option because of its high phosphorus content and excellent biocompatibility. However, its combustion behaviors and chemical kinetic mechanisms remain unclear. In this study, quantum chemical calculation methods were used to construct a detailed PA chemical reaction kinetic model. A series of experiments were conducted to validate the model and evaluate PA's flame suppression effect. Utilizing a counterflow flame burner and particle image velocimetry (PIV), the inhibitory effect of various PA concentrations was examined based on the laminar flame speed of CH4/PA/Air mixture. The results revealed that a merely 0.2 % addition of PA could reduce the laminar flame speed by 38.9 %, demonstrating its significant flame suppression effect. Building on the foundational GRI-Mech 3.0 and integrating PA's pyrolysis and reaction mechanism, this study developed for the first time a detailed chemical model of CH4/PA/Air combustion. This model integrated PA's thermal decomposition module and thermodynamic data via ab-initio quantum chemical calculations, thereby accurately predicting global kinetic indicators such as laminar flame speed. Results suggested that the key reactions, such as PO2+H + M→HOPO + M, HOPO2+H→PO2+H2O, and HOPO + OH→PO2+H2O primarily influenced the laminar flame speed. Moreover, the CFD simulation elucidated the complex interaction between PA and flame structures. A detailed analysis of the spatial distribution of key parameters such as temperature, combustion radicals, and effective inhibition radicals unveiled the PA's flame suppression mechanism in support of the practical application of this eco-friendly flame retardant.

Application of STPA for Comprehensive Risk Analysis of Naphtha Explosion Hazards

Chemical accidents always result in significant losses due to the flammable, explosive, and toxic characteristics of hazardous chemicals. Analysis of process safety parameters is an effective way to prevent hazardous chemical accidents and reduce losses. System-theoretic process analysis (STPA) is a newer hazard analysis technique that is based on systems theory. It has been shown to be effective in identifying hazards in other industries, but its application in oil and gas plants is still rare and limited due to systems complexities and other challenges. This paper aims to apply the STPA method to a complex system “column C-63” at the Skikda RA1K refinery to prevent the explosion scenario of naphtha. The results show that STPA was able to identify the root causes of the explosion scenario, which is important for preventing chemical risks.

Flame Retarded Adhesive Tapes and Their Influence on the Fire Behavior of Bonded Parts

AbstractPressure-sensitive adhesive tapes are used in automotives, railway vehicles and construction, where flame retardancy is of major importance. This is why industrial applicants often buy, and industrial tape manufacturers often produce, flame-retardant adhesive tapes, advertised for their good flammability characteristics. Yet, how flame-retardant tapes influence the fire behavior of bonded materials is a rather open question. To investigate this issue, three different substrates were bonded, using eight double-sided adhesive tapes containing two different carriers and two different flame retardants. The bonded substrates were compared to their monolithic counterparts in terms of flammability, fire behavior and fire stability. The fire behavior of adhesive tape bonded materials differed significantly from the monolithic substrates. The usage of different adhesive tapes let to different burning behavior of the bonded materials mainly due to different carrier systems. In contrast, the implementation of flame retardant into the adhesive had rather minor or no effect on the burning behavior of the bonded substrates despite their positive effect on the flammability of the free-standing tape. The carrier changed the HRR curve in the cone calorimeter and was able to both, reduce and increase fire hazards. Using the carrier with the better fire performance can lower the fire growth rate by 20%, the peak of heat release rate by 27%, and the maximum average rate of heat emission by 30% in cone calorimeter tests. Overall, the fire behavior of bonded materials is a complex interaction between substrate, adhesive, and carrier, and depends on the fire scenario the materials are exposed to.

Effect of flameholding cavity geometry on the flowfield of a solid fuel scramjet

An optically accessible solid fuel scramjet was used to investigate the supersonic combustion of varying polymethyl methacrylate solid fuel grain geometries. The rear wall angle of the flameholding cavity was varied (30, 60, 75, and 90°) and an alternative geometry (flush fuel grain) containing the addition of a backwards facing step to the front of a conventional fuel grain was explored. Optical diagnostics including high-speed shadowgraph, CH* chemiluminescence, and HD video were used to analyze flammability characteristics and determine quantitative regression rates for each geometry. The optical results were supplemented by static pressure traces along the length of the combustor for the duration of a test firing. All tests were conducted with Mach 2 inlet flow into the combustor at nominal inlet conditions of 12.9 atm and 900 °C. Shadowgraph imaging for both cold flow and combusting flow was used to characterize the varying flow fields associated with their respective geometries and their core flow oscillatory frequencies were preliminarily inspected. Chemiluminescence data reveals increased heat release in the downstream constant area and expansion sections of the flush fuel grains compared to conventional geometries. This heat release appears to correlate with increased time-averaged regression rates in these regions while the varying cavity angle fuel grains demonstrate differing magnitudes of maximum regression along the rear cavity wall and onset of the constant area section. In addition to increased overall regression rates, flush geometries increase the flameholding capabilities and demonstrate self-sustained burning at lower inlet temperatures than similar geometries designed without a flush section.

A LITERATURE REVIEW OF KEY FINDINGS IN FUNDAMENTAL FOREST FIRE RESEARCH

The purpose of this review is to examine key findings in the fundamental research of wildfire flammability characteristics. The review begins with a brief introduction, highlighting the growing need for more detailed research into the development of forest fires due to increasingly pronounced climate changes. This is followed by an overview of the application of devices operating on the principle of calorimetry, emphasizing additional possibilities for setting and adjusting these devices. Upon reviewing the literature, it becomes evident that the majority of research on the flammability of forest vegetation is primarily focused on the moisture content levels in fuels. For this reason, the third part of this paper is dedicated to exploring the influence of moisture content on the flammability of forest vegetation. Towards the end, an overview of the types and possibilities of igniting forest fuel is provided, with a particular emphasis on the creation of firebrands as a source of ignition for vegetative fuel.

Environmentally friendly fire retardant natural fibre composites: A review

There is a growing drive in replacing conventional non-renewable fibres such as glass and carbon reinforced composites with more sustainable and renewable reinforcements such as flax, hemp, jute in biobased composites in key industry sectors such as automotive, marine, building and construction motivated by lower carbon footprint and sustainability. Despite this drive, flammability characteristics of these sustainable biobased composites are not fully understood. Through an up-to-date review, this article meticulously discusses the theme of bio-based and eco-friendly flame retardants (FRs), delving into their intricate mechanisms, flammability testing methodologies, and emerging research trends. It underscores the pivotal necessity of developing tailor-made eco-friendly FRs customised for a diverse range of materials to bolster fire safety in sustainable material applications. Furthermore, it illuminates the limitations associated with prevalent methods for assessing flammability and advocates for advancements in dynamic testing and multi-scale analyses to more accurately simulate real-world fire scenarios. This review also highlights the key characteristics of natural plant fibres and their composites critical for the development of sustainable and fire safe materials for key applications areas. Additionally, it highlights the diverse spectrum of strategies employed in the realm of flame-retardant materials research, emphasizing a pronounced shift towards eco-friendly alternatives, innovative coatings, and the ongoing exploration of synthetic biopolymers, nanocomposites, and fibres in the pursuit of heightened fire safety. Amidst the inherent challenges, this comprehensive review unequivocally underscores the pivotal role of interdisciplinary research collaboration in driving forward fire safety within the domain of sustainable materials.

Research on the lubricating oil leakage characteristics in the vapor compression heat pump system under refrigerant leaking

Refrigerant leakage is a situation that often occurs in refrigeration equipment such as heat pumps. However, certain alternative refrigerants, while exhibiting superior environmental performance, possess varying levels of flammability. The leakage of flammable refrigerants into confined spaces can pose a significant risk of explosion. The amount of lubricant in the leaking refrigerant will undoubtedly affect the flammability characteristics of the refrigerant. In this paper, the content of PVE32 oil in the leaking refrigerant during the operation of a heat pump was investigated. The results showed that, under the five leakage rate scenarios set up in the experiment, the oil concentration was highest when the leakage occurred at the condenser inlet and lowest when the leakage was at the evaporator outlet. During the leakage process of the experiment, as the mass flow rate of the leakage increased, the oil content in the early stage of the leakage increased, but the oil content in the late stage of the leakage decreased. The reasons for the change in oil content were analyzed by the oil circulation rate and the degree of phase separation. The decrease of the oil circulation rate and the change of the degree of phase separation were the key factors affecting the magnitude of the oil content as the leakage proceeded. The results of the study reveal the leakage characteristics of lubricating oil with refrigerant leakage.

Comprehensive risk assessment of flammable refrigerants in HVAC systems based on Bayesian networks and consequence modeling

Promoting environmentally friendly refrigerants is a global imperative. However, their excellent thermal properties often come with flammability risks, raising concerns about HVAC safety. Existing studies focus on basic flammable characteristics and concentration distribution, neglecting comprehensive risk assessment for refrigerant leakage, diffusion, and fire. This paper fills this gap by constructing a comprehensive risk assessment model. The model integrates Bayesian networks to analyze causes of refrigerant leakage and employs CFD to evaluate distribution and residence time of flammable clouds, ignition sources, and consequences of ignition. Validation using real incident events quantitatively assesses risks associated with leaks, flammable cloud migration, ignition probability, and fire hazard. Critical failure points like improper welding and compressor exhaust are identified. Increasing ventilation speed from 0 to 1 m/s and 2 m/s reduces fire probability from 1.65 × 10−9 to 1.0 × 10−9 and 2.5 × 10−10, respectively. Effective measures to reduce leakage and fire risk are proposed based on accident experience and risk acceptability. The model is applicable not only to R290 chillers but also to other vapor compression cycles, aiding safety measures and emergency response plans for accidents involving flammable refrigerants in HVAC systems.

Study on flammability limit and combustion reactions behaviors of R744/R152a environmentally friendly mixed working fluid by experiments and molecular dynamic simulation

R744/R152a mixture has broader application prospects. However, its thermodynamic and safety characteristics need to be fully considered. This paper presents the flammability characteristics and reaction mechanism of R744/R152a mixture by experimental and ReaxFF MD. Firstly, the flammable zones of the mixture with different ratios were tested on a high-precision experimental setup. Using a high-speed camera and an infrared thermographic record flame evolution characteristics and relative flame temperature of the mixture both lean and rich limits. The flammable zones of R152a are 0.386–0.685 (Φ) at y = 0. R744 was able to narrow the flammability zones of R152a. As the inert gas increases, the lean and rich limits merge, is 0.542 (Φ). Based on experimental studies, the inhibitory effect of R744 on the oxidation mechanism of R152a was investigated from the atomic level using ReaxFF MD. The results showed that the R744 increased the activation energy of the system from 52.08 kcal/mol to 55.73 kcal/mol, 52.18 kcal/mol, 57.04 kcal/mol, 52.93 kcal/mol, 52.98 kcal/mol, respectively. Reaction pathways and the rates of elementary reaction are significantly suppressed. The simplified mechanism of the oxidation can reveal the macroscopic phenomenon that R744 inhibits flame propagation. The results of this study provide safety guidance for R744/R152a applications.

Straightforward synthesis of novel chitosan bio-based flame retardants and their application to epoxy resin flame retardancy

Epoxy resin (EP) is widely used in various industries. However, its inherent flammability characteristics limit its application, so there is an urgent need to develop bio-based flame retardants for efficient flame retardant EP. Chitosan (CS) is one of the most commonly used bio-based raw materials, but most chitosan-based flame retardants are synthesised using large amounts of organic solvents, with low yields and not in line with the theme of green and sustainable development. In this paper, we report a facile, eco-friendly, and solvent-free approach to chitosan-based flame retardants. A novel full biomass flame retardant, chitosan-based ammonium phytate (PUCS), was synthesised without the organic solvent by using chitosan and phytanic acid as raw materials and the electrostatic adsorption interaction between them and urea, and it was used as a flame retardant additive for EP. The results showed that the EP samples with 7.5 wt% PUCS added increased the limiting oxygen index from 22.2 % to 32.2 % and the vertical burning rating from no rating to V-0. Moreover, the cone calorimeter test results showed that the EP/PUCS composites with adding PUCS showed a significant decrease in the peak heat release rate, and it has excellent flame retardancy. It is worth mentioning that the mechanical property test results showed that the mechanical properties of EP/PUCS composites with adding PUCS could still reach the scope of the needs for engineering applications. This work provides an economical, convenient, and eco-friendly feasible route for bio-based flame retardants.

Synthesis of cerium-based flame retardant containing phosphorus and its impact on the flammability of polylactic acid

The synthesis and characterization of [Ce2(PPPA)4(OH)2]·4H2O, wherein PPPA denotes 3-(hydroxy(phenyl)phosphoryl)propanoate, were conducted. Its potential as a flame-retardant additive for poly(L-lactic acid) (PLA) in conjunction with ammonium polyphosphate (APP) was investigated. Remarkably, with just incorporation of the 1 % Ce-complex and 4 % APP, the resulting PLA composite (PLA-8) meets the V-0 standard, exhibiting an impressive limiting oxygen index (LOI) of 29.4 %. Moreover, the introduction of the Ce-complex leads to a significant extension of ignition time (TTI), a significant 24.1 % decrease in total heat release (THR) compared to pure PLA, and a notable increase in residual carbon rate from 0.3 % to 3.51 %. Although PLA-8 exhibits a minor decline of 8.7 % in tensile strength and 3.4 % in elongation at break, respectively, compared to pure PLA, there is a substantial improvement of 32.2 % in Young's modulus and 29.9 % in impact resistance. These results emphasise the potential of cerium-based phosphorus-containing flame retardants, with cerium playing a key role in enhancing the flammability characteristics of PLA. This study contributes to the development of sustainable and fire-resistant materials in polymer chemistry.