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The goal of this work was to develop acrylonitrile-butadiene (NBR) elastomer composites filled with hydroxyapatite (HAP) characterized by improved cure characteristics and resistance to burning. Silane, i.e., (3-aminopropyl)-triethoxysilane, ionic liquid, i.e., 1-decyl-3-methylimidazolium bromide and surfactant, i.e., cetyltrimethylammonium bromide, were used to improve the filler's dispersibility in the elastomer matrix and to reduce the time and temperature of vulcanization. The effects of HAP and dispersants on the cure characteristics, crosslink density and physico-chemical properties of NBR composites were explored. The additives used, especially the ionic liquid and surfactant, effectively improved the dispersion of HAP in the NBR matrix. The amount of HAP and the dispersant used strongly affected the cure characteristics and crosslink density of NBR. The optimal vulcanization time significantly increased with HAP content and was pronouncedly reduced when ionic liquid and surfactant were applied. In addition, ionic liquid and surfactant significantly lowered the onset vulcanization temperature and improved the crosslink density and hardness of the vulcanizates while impairing their elasticity. HAP and dispersants did not significantly affect the damping properties or chemical resistance of NBR vulcanizates. Above all, application of HAP considerably enhanced the resistance of vulcanizates to thermo-oxidative aging and reduced their flammability compared with the unfilled NBR.

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The article presents the results of research on the impact of the use of an original, innovative method of deposition of Parylene C on the functional properties of fabrics with various potential applications (e.g., thermal and chemical protective clothing, packaging, covers and others). Verification of the effects of the method used was based on interdisciplinary research taking into account the impact of coating fabrics on changes in their structure (micro-CT), surface properties (contact angle), barrier properties (water and chemical liquid wetting), electrostatic properties (charge decay), biophysical properties describing heat and mass transfer (by the Alambeta system and thermal imaging) and flammable properties. Four fabrics made of synthetic organic fibres (meta-aramid, para-aramid) and natural inorganic fibres (basalt) were selected for testing. Given the complex structure of textile substrates, the results confirmed that the two assumed thicknesses of the Parylene C coating were consistent with the actual measurements. The findings indicated that the coatings significantly reduced water and acid absorption in the fabrics compared to unmodified ones. Thermal insulation property tests revealed that coated fabrics exhibited higher thermal conductivity than unmodified fabrics. Additionally, the presence of Parylene C on aramid fabrics resulted in a modest increase in their ignition resistance.

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This paper presents a study of the flammability and thermal decomposition products of glass fiber-reinforced epoxy resin (GFRER) with the addition of cardanol-based phosphorus-containing benzoxazine monomer (CBz) and graphene and their combinations in different proportions (up to 20 wt.%). The addition of CBz alone or in combination with graphene resulted in an increase in the limiting oxygen index (LOI) and self-extinguishing in the UL-94 HB test. The flame-retardant samples had better tensile mechanical properties than the sample without additives. The differential mass-spectrometric thermal analysis (DMSTA) of the thermal decomposition products of GFRER without additives and with the addition of CBz and graphene was carried out. CBz addition promoted the thermal decomposition of high-molecular-weight products of epoxy resin decomposition in the condensed phase and at the same time decreased the time of release of low-molecular-weight thermal decomposition products into the gas phase. Graphene addition resulted in an increase in the relative intensities of high-molecular-mass peaks compared to GFRER without additives.

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After the period of halogenated compounds, the period of nano-structured systems, and that of phosphorus (and nitrogen)-based additives (still in progress), following the increasingly demanding circular economy concept, about ten years ago the textile flame retardant world started experiencing the design and exploitation of bio-sourced products. Indeed, since the demonstration of the potential of such bio(macro)molecules as whey proteins, milk proteins (i.e., caseins), and nucleic acids as effective flame retardants, both natural and synthetic fibers and fabrics can take advantage of the availability of several low-environmental impact/"green" compounds, often recovered from wastes or by-products, which contain all the elements that typically compose standard flame-retardant recipes. The so-treated textiles often exhibit flame-retardant features that are similar to those provided by conventional fireproof treatments. Further, the possibility of using the same deposition techniques already available in the textile industry makes these products very appealing, considering that the application methods usually do not require hazardous or toxic chemicals. This review aims to present an overview of the development of bio-sourced flame retardants, focusing attention on the latest research outcomes, and finally discussing some current challenging issues related to their efficient application, paving the way toward further future implementations.

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The growing requirements regarding the safety of using polymers and their composites are related to the emergence of more effective, sustainable, and hazardous-limited fire retardants (FRs). Significant amounts of FRs are usually required to effectively affect a polymer's burning behavior, while the knowledge of their recycling potential is still insufficient. At the same time, concerns are related not only to the reduced effectiveness of flame retardancy but also, above all, to the potential deterioration of mechanical properties caused by the degradation of temperature-affected additives under processing conditions. This study describes the impact of the four-time reprocessing of bio-based polyamide 11 (PA11) modified with an intumescent flame-retardant (IFR) system composed of ammonium polyphosphate (APP), melamine cyanurate (MC), and pentaerythritol (PER) and its composites containing additional short basalt fibers (BFs). Composites manufactured via twin-screw extrusion were subjected to four reprocessing cycles using injection molding. A comprehensive analysis of their structural, mechanical, and fire behavior changes in each cycle was conducted. The obtained results confirmed the safety of using the proposed fire-retarded polyamide and its composites while reprocessing under the recommended process parameters without the risk of significant changes in the structure. The partial increase in flammability of reprocessed PA-based materials caused mainly by polymer degradation has been described.

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This research studies natural rubber (NR) composite blends prepared with recycled polyethylene (PE), polyurethane waste (PU), silica (SiO2), and aluminum trihydroxide (ATH) under the proper mixing conditions using an internal mixer and a two-roll mill. The mechanical, impact, dynamic mechanical, and thermal properties, together with flammability, were investigated. NR/PU composites filled with a specific SiO2/ATH concentration resulted in excellent flame-retardant properties without using PE. Adding PE causes poor flammability, while using PU and SiO2 prevents flame extensibility of the composites. In addition, SiO2 and ATH synergistically improved both mechanical and dynamical mechanical properties. This is attributed to the reinforcement of SiO2 particles inside the matrix, whereas the ATH releases water as a flame retardant. The V-0 composites tested with UL-94 showed acceptable heat resistance, strength, and durability, making them suitable for interior and exterior applications in buildings without the lightweight requirement.

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BACKGROUND: Conducted electrical weapons (CEWs) are nonlethal weapons used in tactical environments. Tactical EMS (TEMS) operators provide patient care in environments where CEWs are present. CEWs may produce a spark that can be a source of ignition. When supplemental oxygen is in use by a TEMS operator, the flammability risk from the CEW is unknown. METHODS: We measured oxygen levels over 20 minutes in an enclosed space with a supplemental oxygen source maximally flowing. Measurements were taken at various distances from the oxygen source to establish baseline concentrations. These concentrations were replicated within a plexiglass box where a CEW was activated to create a sparking arc between probes embedded in a fresh swine shoulder (with skin intact). Various flammable materials, typically found in a patient care setting were used as potential fuel sources. RESULTS: The highest oxygen levels were achieved directly at the source. At 15cm from the source, the maximum oxygen concentration was 31.5%. Within the box, ignition was only achieved at oxygen concentrations greater than 45% and only when human hair was present as fuel. No ignition was achieved at oxygen levels below this regardless of the tested fuel present. CONCLUSION: Ignition from a CEW is possible at supplemental oxygen levels greater than 45% when human hair is present. In an enclosed space, oxygen concentration levels of 45% are only present within 15cm of a flush rate oxygen source. The likelihood of CEW-caused ignition in such settings with supplemental oxygen in use is extremely low.

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Flame retardants (FRs) are added to vehicles to meet flammability standards, such as US Federal Motor Vehicle Safety Standard FMVSS 302. However, an understanding of which FRs are being used, sources in the vehicle, and implications for human exposure is lacking. US participants (n = 101) owning a vehicle of model year 2015 or newer hung a silicone passive sampler on their rearview mirror for 7 days. Fifty-one of 101 participants collected a foam sample from a vehicle seat. Organophosphate esters (OPEs) were the most frequently detected FR class in the passive samplers. Among these, tris(1-chloro-isopropyl) phosphate (TCIPP) had a 99% detection frequency and was measured at levels ranging from 0.2 to 11,600 ng/g of sampler. TCIPP was also the dominant FR detected in the vehicle seat foam. Sampler FR concentrations were significantly correlated with average ambient temperature and were 2-5 times higher in the summer compared to winter. The presence of TCIPP in foam resulted in ∼4 times higher median air sampler concentrations in winter and ∼9 times higher in summer. These results suggest that FRs used in vehicle interiors, such as in seat foam, are a source of OPE exposure, which is increased in warmer temperatures.

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Nowadays, nanotechnology represents a well-established approach, suitable for designing, producing, and applying materials to a broad range of advanced sectors. In this context, the use of well-suited "nano" approaches accounted for a big step forward in conferring optimized flame-retardant features to such a cellulosic textile material as cotton, considering its high ease of flammability, yearly production, and extended use. Being a surface-localized phenomenon, the flammability of cotton can be quite simply and effectively controlled by tailoring its surface through the deposition of nano-objects, capable of slowing down the heat and mass transfer from and to the textile surroundings, which accounts for flame fueling and possibly interacting with the propagating radicals in the gas phase. In this context, the layer-by-layer (LbL) approach has definitively demonstrated its reliability and effectiveness in providing cotton with enhanced flame-retardant features, through the formation of fully inorganic or hybrid organic/inorganic nanostructured assemblies on the fabric surface. Therefore, the present work aims to summarize the current state of the art related to the use of nanostructured LbL architectures for cotton flame retardancy, offering an overview of the latest research outcomes that often highlight the multifunctional character of the deposited assemblies and discussing the current limitations and some perspectives.

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Lithium-ion batteries (LIBs) generate substantial gas during the thermal runaway (TR) process, presenting serious risks to electrochemical energy storage systems in case of ignition or explosions. Previous studies were mainly focused on investigating the TR characteristics of Li(NixCoyMnz)O2 batteries with different cathode materials, but they were conducted in isolation. In this study, the thermal runaway characteristics of prismatic cells that use Li(NixCoyMnz)O2 (with x ranging from 0.33 to 0.9) cathode materials in an inert environment, which are commonly used or proposed for energy storage applications, are examined. The findings of this research show that the normalized gas generation rate remains consistent, regardless of the battery capacity or experimental chamber volume, with a value of 0.1 ± 0.03 mol∙Ah⁻1. High-capacity cells have short jetting durations, and a high nickel content leads to increased mass loss rates. The flammability limits of the gases expelled during thermal runaway, represented by the lower flammability limit (LFL), remain stable at 8 ± 1.8 % with minimal variations. However, the upper flammability limit (UFL) varies significantly, ranging from 30 % to 60 %. Increasing the battery capacity or reducing the experimental chamber volume increases the explosion index. The explosive, combustibility, and jetting duration characteristics of the emitted gases from five different battery chemical compositions provide valuable insights for risk assessment in future electrochemical energy storage systems.

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Current potassium-ion batteries (PIBs) are limited in safety and lifetime owing to the lack of suitable electrolyte solutions. To address these issues, herein, we report an innovative non-flammable electrolyte design strategy that leverages an optimal moderate solvation phosphate-based solvent which strikes a balance between solvation capability and salt dissociation ability, leading to superior electrochemical performance. The formulated electrolyte simultaneously exhibits the advantages of low salt concentration (only 0.6 M), low viscosity, high ionic conductivity, high oxidative stability, and safety. Our electrolyte also promotes the formation of self-limiting inorganic-rich interphases at the anode surface, alongside robust cathode-electrolyte interphase on iron-based Prussian blue analogues, mitigating electrode/electrolyte side reactions and preventing Fe dissolution. Notably, the PIBs employing our electrolyte exhibit exceptional durability, with 80 % capacity retention after 2,000 cycles at high-voltage of 4.2 V in a coin cell. Impressively, in a larger scale pouch cell, it maintains over 81 % of its initial capacity after 1,400 cycles at 1 C-rate with high average Coulombic efficiency of 99.6 %. This work represents a significant advancement toward the realization of safe, sustainable, and high-performance PIBs.

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This research study focused on the effect of adding boric acid to epoxy resin in order to obtain a composite material with improved properties and performance. To this end, a fine powder of boric acid (H3BO3) was introduced into epoxy resin in different amounts, i.e., 0.5 g, 1.0 g, and 1.5 g. As the matrix of the epoxy composites, styrene-modified epoxy resin based on bisphenol A (BPA) (Epidian 53) was used. It was cross-linked with two types of curing agents, i.e., an amine (ET) and a polyamide (PAC). The mechanical properties of the obtained epoxy composites (in terms of compressive strength, compressive modulus, and compressive strain) were determined at room temperature in order to assess the effect of the addition of boron acid and of the type of curing agent employed to cure the epoxy on these characteristics. Calorimetric measurements were made to highlight any changes in the glass transition temperature (Tg) as a result of the addition of boric acid to epoxy resin. Finally, flammability tests were performed on both Epidian 53/PAC and Epidian 53/ET epoxy composites to analyze their fire behavior and consequently establish the effectiveness of the selected additive as a flame retardant.

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The present work proposes to investigate the effect of an ultrahigh molecular weight silicone rubber (UHMW-SR) and two ethylene methyl acrylate copolymers (EMA) with different methyl acrylate (MA) content on the mechanical and fire performance of a fireproof acrylonitrile butadiene styrene copolymer (ABS) composite, with an optimum amount of ammonium polyphosphate (APP) and aluminum diethyl phosphinate (AlPi). ABS formulations with a global flame retardant weight content of 20 wt.% (ABS P) were melt-compounded, with and without EMA and UHMW-SR, in a Brabender mixer. During this batch process, ABS P formulations with UHMW-SR and/or EMA registered lower torque values than those of ABS P. By means of scanning electron microscopy (SEM), it was possible to observe that all ABS composites exhibited a homogenous structure without phase separation or particle agglomeration. Slightly improved interfacial interaction between the well-dispersed flame-retardant particles in the presence of EMA and/or UHMW-SR was also noticed. Furthermore, synergies in mechanical properties by adding both EMA and UHMW-SR into ABS P were ascertained. An enhancement of molecular mobility that contributed to the softening of ABS P was observed under dynamic mechanical thermal analysis (DMTA). An improvement of its flexibility, ductility and toughness were also registered under three-point-bending trials, and even more remarkable synergies were noticed in Charpy notched impact strength. Particularly, a 212% increase was achieved when 5 wt.% of EMA with 29 wt.% of MA and 2 wt.% of UHMW-SR in ABS P (ABS E29 S P) were added. Thermogravimetric analysis (TGA) showed that the presence of EMA copolymers in ABS P formulations did not interfere with its thermal decomposition, whereas UHMW-SR presence decreased its thermal stability at the beginning of the decomposition. Although the addition of EMA or UHMW-SR, as well as the combination of both in ABS P increased the pHRR in cone calorimetry, UL 94 V-0 classification was maintained for all flame-retarded ABS composites. In addition, through SEM analysis of cone calorimetry sample residue, a more cohesive surface char layer, with Si-O-C network formation confirmed by Fourier transform infrared (FTIR), was shown in ABS P formulations with UHMW-SR.

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Inadequate fire resistance of polymers raises questions about their advanced applications. Flexible polyurethane (PU) foams have myriad applications but inherently suffer from very high flammability. Because of the dependency of the ultimate properties (mechanical and damping performance) of PU foams on their cellular structure, reinforcement of PU with additives brings about further concerns. Though they are highly flammable and known for their environmental consequences, rubber wastes are desired from a circularity standpoint, which can also improve the mechanical properties of PU foams. In this work, melamine cyanurate (MC), melamine polyphosphate (MPP), and ammonium polyphosphate (APP) are used as well-known flame retardants (FRs) to develop highly fire-retardant ground tire rubber (GTR) particles for flexible PU foams. Analysis of the burning behavior of the resulting PU/GTR composites revealed that the armed GTR particles endowed PU with reduced flammability expressed by over 30% increase in limiting oxygen index, 50% drop in peak heat release rate, as well as reduced smoke generation. The Flame Retardancy Index (FRI) was used to classify and label PU/GTR composites such that the amount of GTR was found to be more important than that of FR type. The wide range of FRI (0.94-7.56), taking Poor to Good performance labels, was indicative of the sensitivity of flame retardancy to the hybridization of FR with GTR components, a feature of practicality. The results are promising for fire protection requirements in buildings; however, the flammability reduction was achieved at the expense of mechanical and thermal insulation performance.

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This study focuses on examining the influence of bast fibers on the flammability and thermal properties of the polylactide matrix (PLA). For this purpose, Urtica dioica and Vitis vinifera fibers were subjected to two types of modifications: mercerization in NaOH solution (M1 route) and encapsulation in an organic PLA solution (M2 route). In a further step, PLA composites containing 5, 10, and 15 wt% of unmodified and chemically treated fibers were obtained. The results of the tests show that only biocomposites containing mercerized fibers had a nearly 20% reduced flammability compared to that of PLA. Moreover, the biofiller obtained in this way belongs to the group of flame retardants that generate char residue during combustion, which was also confirmed by TGA tests. The M2 modification route allowed to achieve higher mass viscosity than the addition of unmodified and M1-modified fibers. The reason is that fibers additionally encapsulated in a polymer layer impede the mobility of the chain segments. The inferior homogenization of the M2-modified fibers in the PLA matrix translated into a longer combustion time and only a 15% reduction in flammability.

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Cellulose fabric testing for flame-retardant studies is frequently necessary in various textile applications. Natural cellulose material from ramie (Boehmeria nivea) is being promoted as an alternative raw material for the development of fire-resistant fabrics. This research aims to optimize the coating process of ramie fabric using a phosphorus-based flame retardant (FR) to enhance its flame-retardant characteristics. The FR treatment involves bleaching the fabric with H2O2; followed by fabric finishing using a formula comprising 3% (v/v) hydroxymethyl resin; phosphoric acid (2%); and two formulations of the flammable agent Flamatic DM-3072N: 40% (v/v) and 50% (v/v), applied using the pad-dry-cure method. The flame-retardant properties of the treated fabric are evaluated through flammability testing based on the ASTM D6413-08 standard, limiting oxygen index (LOI) analysis, and micrograph surface structure analysis with SEM. The results indicate that ramie fabric treated with the FR-50% material exhibits superior fire resistance, preventing fire spread on the fabric with a char length of 15-30 mm and a LOI value of 29. These findings highlight the potential of FR-treated ramie fabrics for various industries, including the automotive and protective clothing industries.

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The influence of air humidity on flame propagation in mixtures of hydrofluorocarbons (HFCs) with air was studied through numerical simulations and comparison with measurements from the literature. Water vapor added to the air in mixtures of fluorine rich hydrofluorocarbons (F/H≥1) can be considered as a fuel additive that increases the production of radicals (H, O, OH) and increases the overall reaction rate. The hydrofluorocarbon flame is typically a two-stage reaction proceeding with a relatively fast reaction in the first stage transitioning to a very slow reaction in the second stage which leads to the combustion equilibrium products. The transition to the second stage is determined by the consumption of hydrogen-containing species and formation of HF. Despite a relatively small effect of water on the adiabatic combustion temperature, its influence is significant on the reaction rate and on the temperature increase in the first stage of the combustion leading to the increase in burning velocity. The main reaction for converting H2O to hydrogen-containing radicals and promoting combustion is H2O+F=HF+OH, as demonstrated by reaction path analyses for the fluorine rich hydrofluorocarbons R-1234yf, R-1234ze(E), and R-134a (F/H = 2). The calculated burning velocity dependence on the equivalence ratio ϕ agrees reasonably well with available experimental measurements for R1234yf and R-1234ze(E) with and without the addition of water vapor. In agreement with experimental data, with water vapor, the maximum of burning velocity over ϕ is shifted to the lean mixtures (near ϕ = 0.8).

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Ozone, widely recognized as an environmentally friendly gas, is extensively used in various textile industry applications. These include pre-treatment processes like bleaching and desizing, as well as creating pattern and vintage effects, wastewater clarification, and surface modification. This study focuses on ozone as a novel solution to a specific challenge: addressing the reduction in flame retardancy properties experienced by flame-retardant (FR) polyester fabrics during post-treatment processes in the production line. Experimentation involved subjecting the fabrics to ozonation and exploring different combinations of ozone flow rates and treatment durations. Mechanical and functional properties of the fabrics were examined, with flammability tested according to International Maritime Organization (IMO) standards. Notably, treatment with a 5 L/min ozone flow rate, a 7.01 g/h ozone concentration ratio, and a duration of 10 min showed significant improvements in IMO values, ensuring compliance with required standards. Furthermore, treated samples underwent comprehensive tests for fastness and strength, yielding results within acceptable ranges. Fourier-transform infrared (FT-IR) and thermogravimetric analysis (TGA) measurements were conducted to evaluate the impact of ozonation. FT-IR results indicated that the presence of C-H groups associated with dyestuff contributed to decreased flame retardancy in the original fabric post-dyeing. However, these groups were effectively eliminated through ozonation, thereby enhancing the fabric's flame retardancy.

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For many years, efforts have been made to reduce the flammability of unsaturated polyester resins (UPRs), which are often used in the rail, shipbuilding, and construction industries. Without modification, they often fail to meet fire safety standards. Despite a rich history of flame retardants (FRs) applied to UPRs, researchers seek new solutions that will provide lower flammability and smoke density, as well as attaining a lower environmental impact from the composites. The objective of the study is to highlight the most important recent research on promising nano FRs in order to promote their further development. Mechanisms of action of several groups of nano FRs, such as clay-based, carbon-based, transition metal compounds, layered double hydroxides, polyhedral oligomeric silsesquioxanes, and others, including bio-based, have been studied. Particular emphasis has been laid on nano FRs applied to UPRs, and their influences on thermal stability, flammability, and mechanical properties. Moreover, the environmental impact and toxicity of nano FRs have been discussed. Results have proved that nano FRs applied at low loadings may significantly improve thermal stability, with a simultaneous increase or only a slight decrease in mechanical properties. However, attention on related environmental issues has highlighted the necessity of carefully selecting novel nano FRs.

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Limited by flammability, wood and wood-based materials face challenges in distinguishing themselves as structural materials or finishing materials. Once burning, they can produce toxic gases detrimental to humans and the environment. Therefore, it is critical to make clear whether fire-retardant wood construction materials are insusceptible to fire and not the sources of toxic gases. This study aimed to evaluate flame-retardant plywood from the aspects of flammability and the toxic gas and smoke generation during combustion. The flame-retardant plywood was manufactured by impregnating a flame-retardant resin in line with International Maritime Organization (IMO) standards. The research results indicate that seven out of the eight kinds of toxic gases listed by the IMO, other than CO, were not detected during the combustion of the flame-retardant plywood. While CO was detected, its quantities under three test conditions are below the corresponding thresholds. Therefore, unlike synthetic resin products, flame-retardant plywood is a promising finishing material that can reduce the damage from toxic gases in the event of a fire. In the smoke generation tests, the mass reduction rate of flame-retardant plywood increased from 13% to 18% and then to 20% as the test condition became more severe. Under the same circumstances, the average maximum specific optical density also followed an upward trend, whose values (75.70, 81.00, and 191.20), however, still met the IMO standard of below 200. This reflects that the flame-retardant plywood is competent as a finishing material. Further, flammability was evaluated, and the critical flux at extinguishment (CFE), total heat release (Qt), and peak heat release rate (Qp) were determined to be 49.5 kW/m2, 0.21 MJ, and 0.66 kW, respectively, which all did not reach the corresponding thresholds given by the IMO. To sum up, flame-retardant plywood has satisfactory flame-retardant performance and meets fire safety standards, showing the potential to be an attractive finishing material for building and construction.