Fire and Materials最新文献

A new reactive flame-retardant N′-(1-(4-hydroxyphenyl)-1-(6-oxido-6H-dibenzo[c,e][1,2]oxaphosphinin-6-yl)ethyl) benzohydrazide (DOPO-BD) was synthesized via a two-step reaction involving the Schiff base reaction between benzohydrazide and 4-hydroxy acetophenone, followed by a reaction between the imine-based condensation product and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). The chemical structure of DOPO-BD was well characterized by Fourier transform infrared spectra (FTIR), ¹H, ¹³C, ³¹P NMR, and high-resolution mass spectrometry (HRMS). The DOPO-BD was utilized as a reactive flame retardant and co-hardener in DGEBA/DDS. The epoxy composites of varying phosphorus weight percentages were synthesized. UL-94 and LOI tests were used to investigate the flammability of composites. The epoxy composites retained good transparency, which was measured by UV–vis spectroscopy. Thermogravimetric analysis (TGA) observed an increase in the thermal stability of epoxy composites in a higher temperature range with increased char yield. In the UL-94 and LOI tests, EP/DOPO-BD(1.5%P) sample gave a V-0 rating and 30% LOI value. The cone calorimeter test indicated a decrease in total heat released (THR), peak of heat release rate (pHRR), and total smoke production (TSP) for EP/DOPO-BD(1.5%P) in comparison with epoxy (EP). The mechanical properties and glass transition temperature (T_g) of the epoxy composites were determined by Dynamic mechanical analysis (DMA), which showed an increase in storage modulus and a decrease in T_g.

After a highway tunnel fire, the rapid change of the internal ambient temperature directly affects the personal safety of pedestrians. Based mainly on the lateral possibility of fire location and considering the coupling effect of multiple factors in a two-lane highway tunnel, this study systematically carried out 63 full-size tunnel fire simulation studies relying on Fluent software. The smoke temperature distribution patterns in the transverse and longitudinal spaces of the tunnel after the fire were revealed. This study shows that the smoke temperature below the tunnel vault is susceptible to the effect of sidewall restraint, making the maximum temperature of the tunnel vault of the offset fire source large; considering the lateral location of the fire source, the maximum temperature prediction formula of the tunnel vault is modified to expose the change law of the longitudinal temperature decay of the vault. This paper reveals for the first time the law of temperature distribution changes at the characteristic height of the human eye on the evacuation platform in the tunnel; the systematic study of the fire source cross-sectional temperature distribution changes at the key lining structure points, and it is found that a low-temperature space conducive to personnel escape exists in the lower part of the tunnel away from the fire source side. The results of the study are beneficial to the design of safe evacuation paths in the tunnel and the active emergency evacuation of personnel in the near-fire source area.

The increasing threat of forest fires on a global scale is not only a matter of concern due to the potential harm they may cause to both human and animal life but also due to their significant role in exacerbating climate change. In light of these circumstances, one might inquire as to whether forest soil can self-ignite and, if so, under what conditions and at what temperatures this phenomenon may occur. This question is being addressed in the German pilot “Fire science of wildfires and safety measures” of the EU project TREEADS, and the first results are presented below. The importance of basic research into the self-ignition of forest soil cannot be underestimated, as it provides crucial knowledge to prevent forest fires and protect human and animal health. Furthermore, mitigating the occurrence of forest fires can also play a role in reducing greenhouse gas emissions, contributing to global efforts to combat climate change. The procedure of the hot storage test is an effective means of determining whether a material can self-ignite. During the investigation of six soil samples, it was found that five of them were indeed capable of self-ignition. In addition to determining whether the material ignites, the modified hot storage test also analyzed the resulting smoke gases and measured their concentration. The research question of whether regional forest soil is capable of self-ignition can be answered with yes based on these initial tests. Further experiments are needed to determine if self-ignition causes forest fires.

Flame retardant barium phytate (PABA) was prepared by phytic acid and barium carbonate. PABA was used to modify flexible polyurethane foam (FPUF) by “one-step method” to obtain composite FPUF-PABA. The effects of PABA on the thermal stability and combustion properties of FPUFs were studied by smoke density (Ds), cone calorimeter (CONE), thermogravimetric analysis (TGA), and pyrolysis kinetic analysis. The results indicated that the addition of PABA improved the flame-retardant properties of the modified FPUFs. The CONE results showed that PABA significantly reduced the PHRR and total heat release (THR) of FPUF, and FPUF-PABA15 had the lowest PHRR (44.69 kW/m²) and THR (2.49 MJ/m²). TGA showed that FPUF-PABA15 had maximum residual masses of 27.14%, 26.99%, 28.61%, and 27.25% at four heating rates, respectively. Integral programmed decomposition temperature analysis found that FPUF-PABA15 also had the highest decomposition temperature, 225.56, 210.54, 148.83, and 162.13°C at four different heating rates. At the same time, the computational activation energy of FPUF-PABA15 was also the highest, at 133.30, 140.46, and 129.46 kJ/mol, respectively. Ds indicated that FPUF-PABA15 had the best smoke suppression performance, Ds decreased by 2.47 and light transmittance increased by 2.33%. The current results provide a better formulation for bio-based flame retardant-modified FPUF.

Lithium-ion batteries (LIBs) are connected in series during use. State of charge (SOC) difference between two batteries will exist after charging/discharging owing to the capacity or resistance difference between them. This is also seen as SOC inconsistency. SOC inconsistency may cause battery electrical abuse. In this manuscript, a battery testing system, scanning electron microscope, heat furnace, and so on were employed to investigate the influence of SOC inconsistency on electrical performance and thermal runaway (TR) characteristics in 2 serials 1 parallel (2S1P) LIB pack after cycling. The results indicated that the cell with higher SOC in an inconsistent 2S1P pack was overcharged to 4.63 V during first charging, and the cell with lower SOC was over-discharged to 1.90 V during first discharging. The cell with higher SOC became both overcharged and over-discharged gradually with cycles. The cell with lower SOC became neither overcharged nor over-discharged gradually. The electrical performance and TR characteristics of the cell with higher SOC became worse, while that of the cell with lower SOC did not change obviously. The state of health for cells with higher SOC decreased from 100% to 58% after 80 cycles. The time interval between current interrupt device activation and onset temperature of TR for cells with higher SOC was reduced by 183 s, and the maximum surface temperature increased by 34°C.

The full-scale façade standard test is widely employed as a comprehensive method to assess the façade fire spread. Within this approach, the calibration test without combustible façade decouples the intricate interaction between gas-phase combustion and material pyrolysis, which simplifies diagnostics and provides an ideal scenario for model validation. This paper presents large eddy simulations (LES) accompanied by comparisons of calibration tests in accordance with JIS A 1310. The calibration tests were conducted to obtain the flame morphologies, gas-phase temperature, and heat flux of over-ventilated façade fires, and the LES modeling is complemented by the modified eddy dissipation model for combustion, the one-equation model for the sub-grid scale turbulence, and the discrete ordinate method with the gray mean absorption-emission approach for thermal radiation. The accuracy of LES data is discussed by comparing with measurements, and the mesh resolution is optimized as 2.5 cm for achieving mesh independency with good qualitative agreement. Furthermore, simulations are conducted to investigate the impact of sidewall distances on façade flame spread. The results highlight that the enhancement of sidewall in façade flame spread occurs under external heat release rate, and the 0.2 m sidewall distance for the designated JIS test is identified as a critical threshold increasing façade thermal load.

The ongoing cladding crisis within the United Kingdom has elevated the need for designers and risk assessors to have the knowledge and tools to evaluate the fire safety of proposed and existing cladding systems. This paper documents efforts to develop a test that could be used to evaluate the fire safety hazards of cladding products that were either proposed for use in design or that were found on existing buildings. Specifically, the products of interest were composite products (i.e., those comprised of multiple layers). The conceptual approach of the European harmonised system was used as a basis for investigating whether a small-scale test could be used to evaluate product fire hazards. A relevant fire scenario was identified, this was linked to candidate large-scale reference tests, and this was linked to performance in a candidate small-scale test. The candidate test showed remarkable agreement with the reference large-scale test, however, many issues were also identified. It was found that, even when specifically intended to accommodate composite products, the small-scale test was unable to always evaluate hazards. Thus the authors were left with the conclusion—regardless of the testing system, there are always products that will not fit the testing system, however hard one tries.

This paper has analyzed the longitudinal ventilation on the effect of the efficiency of the smoke evolution mechanism in a metro tunnel of multi-window carriage fires. These were simulated by Large Eddy Simulation (LES) with Fire Dynamics Simulator (FDS). In the past, analyses of smoke temperature under the tunnel ceiling and smoke overflow characteristics have been conducted. However, longitudinal ventilation has a different impact on temperature than natural ventilation, especially in a subway tunnel with a multi-door carriage fire. Consequently, several simulations were run in a subway tunnel (360-m long, 6.0-m wide, and 4.8-m high). The longitudinal ventilation velocity is set by 0–10 m/s with the heat release rate of 1–10 MW. The results show that there is a linear relationship between the maximum temperature and the longitudinal ventilation velocity. An empirical model considering various longitudinal ventilation velocities was developed to predict the maximum smoke temperature underneath the subway tunnel ceiling. The effects of the longitudinal ventilation velocity, the heat release rate, and the distance of the fire source on the characteristics of longitudinal temperature distribution were analyzed. What's more, smoke overflow characteristics under different longitudinal ventilation velocities have been described. The findings and results can also provide a reference for the fire risk assessment of a metro tunnel of multi-window carriage fires.

Currently, rural fire protection issues in China loom large, resulting in frequent fire incidents due to an inadequate rural fire infrastructure and insufficient firefighting resources. Consequently, prompt fire suppression becomes challenging, leading to significant casualties and economic losses. To address these challenges and align with the national rural revitalization strategy, our research team dedicated 5 years to meticulously scrutinizing fire incident data in China spanning from 2012 to 2022, alongside an extensive review of international documents. We conducted on-site investigations in rural areas across 63 cities in 11 provinces, including Anhui and Jiangsu. By analyzing fire data and field investigation results, we identified the causes and percentages of 11 types of rural fires, as well as summarized five types of rural fire hazards and six types of rural fires. Drawing from insights gleaned from the experiences of countries such as the United States, Australia, Canada, and South America, we have formulated eight policy recommendations for rural fire protection, encompassing aspects like organization, responsibility, planning, construction, operation, and maintenance, as well as public awareness. Therefore, we anticipate that this study will catalyze enhancing rural fire protection efforts in China and other developing nations.

This paper reports an experimental campaign to evaluate the residual mechanical resistance after high temperatures of two structural masonry components: block and mortar. Residual compressive strength and deformation modulus of four different hollow concrete blocks and two different mortar mixes after heating at high temperatures are investigated. The test method used was the one recommended by RILEM TC 200 for mortars and an adaptation of the same method proposed by Medeiros et al. suitable for the geometry of hollow blocks. Despite the sharp drop in the deformation modulus after heating blocks and mortar, no different behaviours are observed in the deformability of the materials caused by the variables studied. The same cannot be said in relation to the variation of the residual compressive strength of the blocks, which is affected by the variables: initial nominal compressive strength and width of the concrete block. Regarding laying mortars, the results confirmed the small influence of compressive strength on the evolution of residual mechanical strength. The data and analyses reported here on the residual mechanical properties of hollow concrete blocks produced from a concrete mixture of very dry consistency, vibro-pressed and with normal weight aggregates are relevant, since the data found in the literature generally refer to the wet cast concrete material and in cylindrical bodies.