Fire and Materials最新文献

The present work deals with the thermal degradation, the physical characterization, and kinetic mechanisms of green epoxy resin-based biocomposites (BC) reinforced by banana leaf fiber (BLF). The two main samples have been manufactured using the vacuum bag resin transfer molding method. The first, BLF-based BC, is used as a control sample, while the second sample is coated with 6% wt. of intumescent fire retardant (IFR), which contains APP and boric acid. The effect of IFR coating has been investigated using thermogravimetric analysis (TGA) under inert and oxidative atmospheres and kinetic studies of model-free and model-based approaches have been applied for predicting the kinetic parameters of thermal degradation reactions. The TGA results show that the IFR coating delays the thermal degradation around 13–20 K of BLF-based BC materials, which leads to an increase of 8% in the char residue under inert atmosphere. In addition, the sample has been characterized by SEM, EDS, and FTIR analysis (before and after the TGA test). The effectiveness of the IFR protective role is displayed on the SEM micrographs by showing the hole of the char enclosed and built the foam layer. The kinetic parameters from model-free and model-based curve fitting of BLF-based BC and BLF-based BC-coated IFR are obtained, while the effect of IFR on the kinetic parameter increased the activation energy (model-free and model-based) under inert atmosphere. The fitting methods and optimization procedure gave excellent results for kinetic parameters, showing a particularly good correspondence with the TGA experimental data.

DL-malic acid (DMA), as a recognized antioxidant inhibitor and chelating agent in the food and chemical industries, has good application prospects in coal fire prevention and control. This paper investigates the impact of a DMA solution on the surface properties and phase structure of coal through a range of analytical techniques, including electron microscope scanning, particle size analysis, and x-ray diffraction. The thermal behavior characteristics of DMA-treated coal were analyzed using thermogravimetric experiments. The results show that after adding malic acid, the particle size of coal sample is reduced, the sphericity and roundness are reduced, and the pore size is increased. The hydroxyapatite and calcite components in coal were dissolved and consumed, and the calcite components were gradually depleted with the increase of DMA concentration. The flocculent structure produced by the condensation of the crushing residue and broken small particles are attached to the internal pores of coal, which reduced the coal oxygen contact sites and increases the content of the sealed solution, resulting in the increase of the thermal characteristic temperature of the coal and the inhibition of the oxidation heat generation process. DMA has obvious inhibitory effect on fresh coal and oxidized coal, and the inhibitory effect is stronger on high-temperature oxidized coal. Therefore, DMA can be effectively applied to the prevention and control of spontaneous combustion of residual coal in goaf. The research results provide a reference for the research of coal fire prevention technology and the preparation of environmentally friendly flame retardant materials.

This paper provides an experimental investigation of a kerosene/air burner (the NexGen burner designed on the FAA's proposed ISO 2685 standard), which is used to generate flame/burnt gases impinging on material samples in the field of fire safety. The purpose of this study is to characterize this burner, and experimental means are implemented to better understand the effects of the equivalence ratio on the spatial distribution of the gas temperature (thermocouples), the heat flux (heat flux gauge), and gas emission species. Hence, the measured flame temperature, heat flux, and heat release rate increase up to a critical value of equivalence ratio equal to 1.03. Furthermore, a pyrolysis test was carried out on composite materials and the results of the comparative analysis of carbon-phenolic, carbon-BMI, and carbon-PEKK materials show that carbon-PEKK had the lowest mass loss, highest back-face temperature without significant material delamination, and the lowest concentration of gas emission species.

Analysis of the Fire Brigade's database of fires in London between 2009 and 2020 provided insight into the level of fire safety in the city and how it varies across different types of dwellings and different levels of protection. Regarding the number of fires, fatalities, and injuries, fire safety in London has significantly improved on average over these years. However, average trends cannot analyze catastrophic fires with multiple fatalities, like at Grenfell Tower in 2017, as these events are too rare to form a suitable sample size. Dwelling fires are the most lethal in London: despite accounting for only 28% of fires, they lead to 87% of fatalities and 83% of injuries. The odds of a dwelling fire becoming fatal in London fell from 1 in 174 in 2009 to 1 in 208 in 2019, a decrease of 16%. The total number of fires has decreased over this period, and the number of fires where an alarm was raised has increased, suggesting that the prevention and detection layers of fire safety have improved, while our analysis suggests that the level of protection from the compartmentation and evacuation layers has remained constant over time. An analysis of the different layers of fire protection suggests that compartmentation was the most impactful layer, with a failure in compartmentation increasing the odds of a fire being fatal by 1.5 to 5 times. Overall, this analysis shows that the fire hazard to Londoners in general is low and the lowest since 2009; however, there is still a threat that should not be understated.

This paper presents the fire load data in educational, office and library buildings, obtained through an extensive inventory survey. This data collection effort is prompted by a growing need to simulate compartment fires, wherein estimating realistic fire scenarios is essential to assess the level of fire severity in a structure, and consequently the strength of the various structural members at elevated temperatures. The attributes of compartment fires primarily depend upon the fuel load and its composition, compartment dimensions, ventilation characteristics, and construction materials. Despite an acute need, fire load data across the world is scarce and outdated, and does not reflect the change in the type of materials in-use today. The survey data presented in this paper is collected from 108 rooms in 10 educational buildings, 51 rooms in three office buildings, and 13 rooms in a library building. This paper also presents the composition of fire loads and the levels of ventilation in these buildings. The studies show that fire loads can vary significantly depending on the room-use; thereby basing fire load values solely on the overall category of a building may result in either conservative or unsafe design. This study also finds that certain room types (e.g., computer labs) have significant plastic-based fuels, indicating that typical modelling recommendations based on cellulosic fuels for heat release rate, combustion heat, etc. may not always be appropriate. The paper finally examines the statistical distribution that best describes the measured values of the fire load densities.

To investigate the fire danger of mattresses, combustion experiments were conducted with a mattress installed at different heights above the floor to better understand their combustion behavior. The installation height was varied because the height of a mattress varies depending on the bed frame, and the combustion behavior is expected to change with the installation height. Experiments with a mattress installed at 0–515 mm above the floor revealed that the fire growth was faster, and the maximum heat release rate (HRR) increased with installation height. In contrast, in a series of experiments where a mattress was installed above a water pool, the flame spread rates and HRR histories were comparable for all installation heights. This demonstrate that the combustion behavior of the mattress was affected by the combustion of the molten mattress material that dropped to the floor, and this effect was influenced by the mattress installation height. Furthermore, we analyzed the HRR per unit area of mattress construction material using cone calorimeter tests to mimic the combustion taking place on the floor. Combining these results with the relation between the length of the burning part of a mattress at the front of flame spread and the HRR, we proposed a model for predicting the HRR history of mattress for a flame ignition at the center of its longitudinal side. The derived predictive model for the HRR history of mattress combustion emphasize that it is necessary to understand factors such as the intense radiant heat from the pool fire.

The ability to accurately identify fire patterns is the fundamental requirement for fire investigations. The corrosion layers of steel in fire scenes exhibit three distinct characteristics. First, due to steel's nonflammable nature, steel patterns can be preserved better at the fire site than patterns formed on other combustible materials; second, both the high temperature and the smoke during the fire affect the high-temperature oxidation process; and third, the corrosion layer of steels inevitably undergoes further evolution after the fire because of the subsequent room-temperature corrosion. This study focuses on investigating Q235 steel because of its extensive use in construction and vehicles. The pattern evolution processes of high-temperature oxidation at elevated temperatures in air, polyethylene (PE), and polyvinyl-chloride (PVC) combustion smoke and the corresponding subsequent corrosion at room temperature were systematically investigated from the perspective of macroscopic and microscopic morphology. The results showed that the smoke atmosphere played an important role in the formation of the corrosion layer of Q235 steel. Compared with samples oxidized in air, samples oxidized in PE combustion smoke exhibited a uniform and dense oxide layer on the surface, which inhibited the corrosion at room temperature further. The PVC combustion smoke accelerated the high-temperature oxidation of the sample, and its influence on the subsequent room-temperature oxidation process was closely correlated with the temperature of the high-temperature oxidation. The results of this study provide important references for understanding the formation of the corrosion layer of Q235 steel for fire investigations.

High fire-resistance polypropylene (PP) composites were prepared by using environment-friendly flame retardants including expandable graphite (EG), red phosphorus (RP), and magnesium hydroxide (MH). Synergism between EG, RP, and MH on the thermo-oxidation behavior and flame resistance of PP was found. The incorporation of MH and RP formed highly thermally stable mixtures of magnesium phosphates consisting of Mg₃(PO₄)₂, Mg(PO₃)₂, and α-Mg₂P₂O₇ at both amorphous and crystalline phases in the burning process. The mixture not only covered the surface of burning materials but also could reinforce the char structure of the PP/EG composites, thereby significantly enhancing the condensed phase flame retardant mechanism of the composites. Mass ratios of the flame retardants were also optimized to obtain the composite with the highest flame retardant efficiency. The result revealed that the combination of EG, RP, and MH in PP at MH/RP mass ratio of 3/2 with only a total additive content of 18 wt.% could make its limiting oxygen index (LOI) increase from 16.8% to 27.2% and the UL-94 rating was improved from none to V-0. In addition, the mechanical properties of the composites were improved via the surface treatment of MH and RP with calcium stearate and silicone oil, respectively.

We highly appreciate the comments by Vytenis Babrauskas on our recently published article entitled, “The curious case of the second/end peak in the heat release rate of wood: A cone calorimeter investigation” by Sanned et al.

We agree with Vytenis Babrauskas regarding the multiple processes involved in the thermal degradation of wood. However, these processes are quite universal when wood burns, and the focus of our article was how the back-face material affects the timing and intensity of the end peak of the heat release in a cone calorimeter. To the awareness of the authors, until now, there has been no study that systematically elucidated the effect of the substrate of the wood-specimen on the end peak in a cone calorimeter. In particular, we have revealed, through experiments, that the thermal boundary condition on the rear side of the wood specimen is critical for the amplitude of the end peak of heat release. In addition, we also observed that the thickness of the specimen affected the time for the occurrence of the end peak.

We do acknowledge that other effects, such as char cracking and time-dependent heat of combustion, may influence the end peak, but our main message is that the thermal boundary conditions and the thickness of the tested specimen are very important for both the amplitude and time of occurrence of the end peak of heat release in a cone calorimeter.

In the future, it would be interesting to investigate a material where most of the heat release occurs due to just one reaction.

During a fire, the load-carrying cross section of timber members will reduce due to charring. This article summarizes experimental investigations into the charring rate of different timber species under standard fire conditions, identifies material properties that contribute to the variations of char rates across the different species, and evaluates the applicability of prescribed charring rates to solid timber, cross-laminated timber (CLT), and glulam exposed to standard fires. Data from the literature showed that density had the greatest impact on charring rate. The charring rate of timber decreased with increasing density, particularly timber densities >700 kg/m³. Prescribed charring rates from current design standards provide reasonable estimates of the average charring rate of timber with densities <700 kg/m³ exposed to standard fire curves. A linear charring rate of 0.65 mm/min was found to be suitable for CLT and glulam exposed to a standard fire for up to 180 min if the CLT did not experience char fall-off. The National Design Specification nonlinear charring model may underestimate the char depth of glulam exposed to standard fire curves for longer than 60 min; however, the percent underestimation was small and limited data was available. The review demonstrated the need for data on the char depths of glulam and CLT exposed to standard fire curves for longer than 60 min and particularly for longer than 120 min.