Fire and Materials最新文献

Two types of ceramifiable flame-retardant room temperature vulcanized (RTV) silicone rubber foam containing mica power (MP) were prepared by using glass powder (GP) as fluxing agents and aluminum hydroxide (ATH) as flame-retardant agent, respectively. The flame retardant, combustion behavior, and thermal stability of ceramifiable flame-retardant RTV silicone rubber foams were investigated. The results show that GP is not conducive to the flame retardancy and thermal stability improvement of the foams. On the contrary, MP and ATH can significantly improve the flame retardancy and thermal stability at high temperatures of the foams. The foams with addition of MP and ATH can reach to a high limiting oxygen index value of 35.8 with V-0 rating in the vertical combustion test, and the total heat release and total smoke production of the foams are 21.0% and 61.7% lower than of the pure RTV silicone rubber foam, respectively. Furthermore, the structural and morphological changes of the foams under different pyrolysis conditions were studied, so as to reveal its ceramifiable mechanism under different fire scenarios. The results show that GP does not promote the formation of more char residue during pyrolysis, but it can greatly lower the ceramifiable temperature, resulting in a superior ceramic phase char residue. The foams including MP and ATH have a high char residue content; nevertheless, a comparatively higher temperature is necessary to create ceramic phase char residue.

To investigate the effects of under-clothing airflows on the thermal protection performance (TPP) and thermal aging of flame-retardant fabrics, we constructed an under-clothing air-gap ventilation device based on the TPP tester. This device can generate different levels of airflow velocities such as 0.17, 1.0, and 2.0 m/s. The flame-retardant fabrics were exposed to a heat flux of 30 kW/m² to simulate an indoor fire scene_. The impacts of under-clothing airflows on the heat transfer behaviors of fabrics were analyzed with the temperature rise measured by thermocouples. The thermal aging behavior of the fabric was investigated based on the outer-shell morphology, mass loss, and residual tensile strength. The results of this study indicated that the under-clothing airflow enhanced the TPP of flame-retardant fabric and the best TPP was achieved under the airflow of 1.0 m/s. Under-clothing airflow increased the post-thermal-exposure mass loss of the fabric but did not further decrease the tensile strength. Higher severity thermal aging occurred for 2.0 m/s airflow than for 1.0 m/s airflow. The findings of this study are important for TPP prediction for firefighters' clothing and will help optimize firefighters' clothing design.

Self-heating during storage of biomass in piles causes material losses, leads to emissions to air, and poses a risk of fire. There are different techniques to assess a biomass material's propensity for self-heating, some of these are briefly reviewed. One of these techniques is isothermal calorimetry, which measures thermal power from materials and produces time-resolved curves. A recently developed and published test standard, ISO 20049-1:2020, describes how the self-heating of pelletized biofuels can be determined by means of isothermal calorimetry and how thermal power and the total heat produced during the test should be measured by isothermal calorimetry. This paper supports interpretation of the result obtained by isothermal calorimetry; the mentioned standard provides examples of peak thermal power and total heat but does not provide any assistance on how the result from isothermal measurements should be interpreted or how the result from measurements on different samples could be compared. This paper addresses the impact of different types of reactions, peak thermal power, total heat released (heat of reaction), activation energy, heat conductivity, and pile size on the temperature development in a generic pile of biomass. This paper addresses important parameters when the result from isothermal calorimetry is evaluated. The most important parameter, with respect to temperature development in large piles, was found to be the total heat released. It was also proposed that safe storage times, that is, the time until a run-away of the temperature in the pile, could be ranked based on the time to the peak thermal power.

The overcurrent fault of copper wire is an important cause of electrical fire, and the combustion process of which is relatively complicated. In this study, the rated current of 32A of the wire was taken, and the electrical fault simulation device was used. After the overcurrent I_o was set to 128A, 160A, 192A, and 224A, respectively, to analyze the combustion evolution process of PVC-insulated copper wire, the evolution of pyrolysis gas from the insulating layer, and the change of functional groups. The results show that when the overcurrent fault of PVC-insulated copper wire happened, the core wire was turning red, the wire was deforming, the smoke was releasing, the insulating layer was dripping, the wire was fusing, and the continuous burning occurred. When the current I_o < 160A, there was only one fusing point on the wire. In addition, when an overcurrent fault occurred in the PVC-insulated copper wire, the temperature rise rate increased exponentially, which can be divided into three stages of the initial heat accumulation stage, the wire fusing stage, and the continuous burning stage. Furthermore, CO, HCl, CH₄, olefins, and aliphatic and aromatic compounds were precipitated during the combustion process of the PVC insulating layer. The quality of the insulating layer decreased with the increase in temperature, and the weight loss rate was higher at 300°C. The conclusions of this study have provided experimental basis and technical support for the physical and evidence identification of fire accidents.

In the hope of studying the laws of secondary explosion induced by gas explosion shock waves lifting deposited coal dust (CD) in coal mines, the paper discusses the explosion overpressure, composite flame propagation characteristics and the acceleration mechanism of composite flame with the aid of a self-built gas explosion experiment pipeline. The experimental results demonstrate that under the methane concentrations of 7.5%, 9.5% and 11.5%, the explosion time-overpressure curves present same variation trend at different measuring points. Specifically, they all surge first, then decrease to a negative value and increase in oscillations, ultimately stabilizing at around 0 MPa. The presence of deposited CD in the reaction has an insignificant impact on the explosion overpressure at the measuring points, and the maximum overpressures all appear near the P2 (0.75 m away from the ignition source) measuring point. However, the deposited CD exerts a considerable influence on the flame's instantaneous velocity, especially on the flame structure during flame propagation. In stark contrast, when the methane concentration is 7.5%, the single flame has a larger instantaneous velocity than the composite flame and it exhibits finger flame, flat flame and tulip flame successively. Compared with the blue flame produced by pure methane combustion, the composite flame shows a bright white light strip that is distributed along the pipeline axis, accompanied by more obvious stratified combustion. The high-pressure wave intensity and the flame front temperature jointly promote the overall turbulence intensity in the area where CD is swept up, resulting in continuous acceleration of the composite flame.

The cover image is based on the Research Article External fire plumes from mass timber compartment fires—Comparison to test methods for regulatory compliance of façades by Johan Sjöström et al., https://doi.org/10.1002/fam.3129.

In this paper, ammonium polyphosphate (APP) and casein (CSN) were added to poly (lactic acid) (PLA) to improve flame retardancy and maintain biodegradability. The flame retardancy, mechanical, and thermal properties of PLA/APP/CSN composites were evaluated, and the optimum ratio of APP and CSN was determined. The results showed that with the addition of 9 wt% flame retardant (APP:CSN=5:4), the limiting oxygen index (LOI) of the PLA/APP/CSN composite reached 28.3%, and passed the UL-94 V-0 rating at 3 mm, char residue increased at 800°C and smoke emission was also significantly reduced compared to addition of APP without the addition of CSN. Besides that, the cone calorimeter result showed that the peak heat release rate and total heat release of the PLA/APP/CSN-5 composite were 18.2% and 13.3%, respectively, lower than those of pure PLA. The addition of flame retardants inevitably led to a reduction in tensile and flex strength values, but the impact strength was improved.

Pyrotechnic-based firefighting systems have been found to be effective in a wide variety of firefighting applications. Binders in pyrotechnic mixtures play a significant role as they consolidate the ingredients, provide excellent mechanical strength and increase the storage life. The rise in health and environmental safety concerns in recent years has directed our research towards natural binder systems of biological origins. Therefore, in this work, galactomannan, also called guar gum, was comparatively investigated against four different types of conventional binders, phenol–formaldehyde resin, ethyl cellulose, hydroxyethyl cellulose and carboxymethyl cellulose sodium salt, which are being used in aerosol-forming pyrotechnic mixtures for firefighting application. It was found that the nature of the binder in an amount of 3% by weight significantly influences the combustion behaviour, fire suppression performance, mechanical and thermal characteristics of gallic acid–KNO₃–KClO₃ tertiary aerosol-forming pyrotechnic mixture for fire fighting application. The safety and performance characteristics of these formulations were evaluated by conducting analyses specific to pyrotechnic formulations, that is, burn rate measurement, heat of combustion, TGA/DSC thermal analysis, hygroscopic study, compression test and n-heptane pool fire suppression test. It can be inferred from the values obtained from these analyses that guar gum is a preferred binder to the other four-binder systems for the gallic acid–KNO₃–KClO₃ pyrotechnic mixture.

The toxicity and density of smoke from 10 commonly used commercial polymer types was studied using the European railway standard EN 45545-2. This test method was chosen because it reflects the current state-of-the-art in assessing the hazards of smoke in bench-scale test scenarios (not because of a specific link to railway applications). The study involves 72 commercially relevant formulations provided by 12 industrial companies. Polymers studied include PE, PP, PC, PA6, PA66, u-PVC, p-PVC, PU, PIR, and epoxy resins. Reference samples as well as samples containing halogenated and Phosphorus, Inorganic or Nitrogen based Flame Retardants (PIN FRs) were tested according to the French tubular furnace method (NF X 70-100) to evaluate their smoke toxicity at 600°C and according to ISO 5659-2 at 50 kW m⁻² with Annex C of EN 45545-2 to evaluate their smoke density as well as toxicity at 4 and 8 min. This study highlights that the measured toxicity and calculated Conventional Indexes of Toxicity (CIT_NLP, CIT_{4 min}, CIT_{8 min}), as well as maximum smoke density (Ds_MAX) show generally no significant increase in the presence of PIN FRs in comparison to the neat polymers. The use of intumescent FRs or hydroxide based FRs generally allows considerable smoke reduction with little impact on smoke toxicity. Bromine based-FRs were found to be detrimental to both hazards in most matrices studied here.