Fire and Materials最新文献

Fire tests were performed for the first time on adhesively bonded timber-concrete composite slabs. The two medium-scale (1.8 × 1.25 m) slabs were produced by gluing an 80-mm thick three-layer cross-laminated timber (CLT) board to a 50 mm thick prefabricated reinforced concrete (RC) slab with epoxy and polyurethane (PUR) adhesives, respectively. The behavior of the composite slabs under elevated temperature was monitored by (1) observing the burning behavior of the used CLT, for example, charring and delamination and (2) measuring the temperature development at different locations of the CLT slabs, in the adhesive bond between concrete and timber boards, and in RC slabs. It was found that employing a one-dimensional charring model for pure softwood, as prescribed by Eurocode 5-1-2, underestimated the charring depth of CLT due to the delamination effects. Measurements revealed that the average charring rates in the middle layer of CLT panels were approximately 0.65 mm/min, suggesting that the presence of concrete does not significantly affect the thermal behavior of the CLT panel. Delamination within the CLT was observed when its adhesive temperature was around 230°C. It was followed by the free-fall of delaminated wood plies, which progressed slowly and lasted until the end of the test. At 90 min into the test, the temperatures of epoxy at the nine locations ranged between 55°C and 130°, while that of PUR between 60°C and 100°. The adhesive between concrete and CLT could lose stiffness significantly along the rising of temperature after surpassing of glass transition temperature (58°C for epoxy and 23°C for PUR in this study). The results indicated a high risk of weakening the composite action between the concrete slab and timber board. The measured temperatures of steel rebar were lower than 50°C. However, the concrete temperature reached about 120°C and the concrete cracked due to the distinct thermal expansions between concrete and timber and the rigid constraint of adhesive bond.

Society's need for safe flame-retardant technologies in passive fire protection is undeniable. To address this concern, this paper presents an experimental investigation of the fire-retardant properties of slash pine wood treated with banana plant pseudostem sap, obtained from a cultivated banana plant variety widely grown in Brazil. The natural sap extract was characterized through X-Ray Fluorescence spectrometry and Fourier Transform Infrared Spectroscopy techniques, revealing the presence of key components, including water, potassium chloride, sodium chloride, sodium silicate, calcium phosphate, sodium phosphate, lignin and tannins. The authors explored different treatment parameters, including various sap impregnation times, number of impregnations and use of natural versus various levels of concentrated sap. First, a horizontal burning test, similar test to UL 94 HB, was used to obtain an initial assessment of the suitability of sap as a flame retardant for slash pine wood. Subsequently, the Mass Loss Calorimeter equipment with thermopile attachment described in ISO 13927:2015 was used to measure various heat release rate parameters. The findings suggest that reducing the water content in sap and increasing the number of repeat treatments results in a more effective treatment for slash pine wood. More specifically, the results indicate that the most efficient treatment involves three impregnations with high-concentration (1/10 volume reduction) sap. Future work to improve the efficacy of the concentrated sap impregnation process could explore the use of pressure treatment instead of soaking.

Pyrolysis models are used in the fire science field to simulate the thermal decomposition of materials. These models require knowledge of the kinetic and thermodynamic parameters of an assumed reaction mechanism, and the thermophysical properties of the virgin material and product species. Standard test methods exist for measuring the thermal conductivity of nonreactive materials, but to date no suitable method exists that is compatible with contemporary pyrolysis models and is applicable to thermally reactive materials. In the present study, a modified methodology was presented and evaluated to address this need. The methodology involves a preliminary assessment of thermal stability, followed by a series of tests including: thermogravimetric analysis, differential scanning calorimetry, and laser flash analysis. Once a reaction mechanism has been identified, gram-scale samples of the virgin and stable product species are isolated and independent measurements of thermal conductivity of those species are obtained. The methodology was applied to eucalyptus fiber hardboard, for which a complete set of property data for pyrolysis modeling was obtained. A pyrolysis experiment was then conducted, and that experiment was simulated using a pyrolysis model parameterized with the measured property data. Model predictions of the mass loss rate and temperature rise of a hardboard sample exposed to radiant heat flux of 35 and 60 kW m⁻² were found to be a good match to measurements. These results demonstrate the suitability of the property data, the pyrolysis model, and the utility of this approach. This work will serve as a basis for property determination in future pyrolysis studies.

Acrylate emulsion is widely used in various industrial fields and is an important polymer emulsion. However, the high flammability limits its application. Besides, acrylate emulsion generally releases a large amount of smoke during combustion. To improve the fire resistance and smoke suppression properties of acrylate emulsions, methyl methacrylate-butyl acrylate copolymer P(MMA-BA)/DOPO-based polymerizable monomer (HEPO)/zinc molybdate sepiolite (Mo-Sep) composite emulsion was prepared by emulsion polymerization, and the effect of Mo-Sep content on the flame-retardant performance, thermal stability, and smoke suppression performance of the composite emulsion was studied. Through microcalorimeter and smoke density meter tests, it was found that the heat release rate (HRR) of the composite emulsion, added with 30% HEPO/3% Mo-Sep, was reduced by 63.3%, and the peak heat release rate (PHRR) was reduced by 72.1%. The total heat release (THR) is reduced by 49.0%, while the peak-specific optical density is reduced by 48.0%. It shows that the composite emulsion has excellent flame-retardant and smoke suppression properties compared to pure MAA-BA emulsion. In addition, scanning electron microscope (SEM) images show that the addition of Mo-Sep increases the density of carbon residue. This composite emulsion may have potential application scenarios in the field of flame-retardant coatings.

With the wide application of epoxy resins in adhesives, electronic packaging materials, and aerospace fields, it is necessary to prepare high-performance flame-retardant epoxy resins to reduce the fire risk caused by their flammability. In this study, the rigid structure intermediate Schiff base (DMDA-SH) was synthesized by condensation reaction of syringaldehyde (SH) with O-Tolidine (DMDA). Then, DMDA-SH-DOPO, a novel P/N-structured biobased flame-retardant curing agent, was synthesized by addition reaction with 9,10-dihydro-9-oxaza-10-phosphame-10-oxide (DOPO) and was applied to the preparation of intrinsic flame-retardant epoxy resin. As expected, DMDA-SH-DOPO has good flame-retardant properties due to the synergistic action of N/P elements. Epoxy resin with only 2.5% DMDA-SH-DOPO (P = 0.16%) can pass the UL-94 V-0 test. Compared with DGEBA/DDM, DMDA-SH-DOPO-7.5's (P = 0.49%) peak heat release rate was reduced by 48.4% and the limiting oxygen index (LOI) reached 27%, making it a flame-retardant material. From the point of view of carbonaceous residue performance, the expansion height of carbon residue after DMDA-SH-DOPO-7.5 combustion is significantly increased, and the amount of carbon residue at 800°C is increased by 36.4%. In addition, appropriate DMDA-SH-DOPO can effectively improve the bending property of epoxy resin. This study provides a new idea for preparing renewable high-performance intrinsic flame-retardant epoxy resin.

Electrical fires perennially rank first in fire occurrence types, with conductor overcurrent being one of the main inducements. This topic draws significant attention from scientific researchers and fire investigators. To understand the overcurrent fault and combustion characteristics of copper-clad aluminum conductors, this paper examines 2.5 mm² copper-clad aluminum conductors that meet national standards, investigating morphological changes, temperature variations in the core and insulation layer, and flame propagation patterns under overcurrent conditions. Experiments using an electrical fault simulation device were conducted to study overcurrent failures of copper-clad aluminum conductors under 52.5–105 A conditions. The results indicate that when the current exceeds 67.5 A, the conductor undergoes a series of changes during energization, including smoking, expanding, carbonizing, burning, and breaking; at 52.5 A, the insulation layer reaches thermal equilibrium at 150 s without combustion; for currents between 60–67.5 A, wire core temperature variations can be divided into three stages; at 75 A, the insulation layer reaches thermal equilibrium 10s before breaking; currents above 82.5 A see a sharp increase in temperature in both the core and insulation layer before the conductor breaks; above 97.5 A, the conductor first breaks and then burns. The research results have significant theoretical value in improving the scientific rigor of fire accident investigations and forensic evidence examinations.

The outermost layer of a fire proximity suit needs to conform to a strict requirement of radiant protection performance (RPP) ≥ 20s, which is indicative of its ability of offering a protection for at least 20s duration from second degree burn upon radiant heat exposure (84 kW/m²). Typically, this layer is fabricated by laminating a single-side metallized PET (SMPET) layer with glass fabric. However, upon erosion of the deposited metal, this laminate is rendered unsuitable due to loss of reflectivity. Here, we explore the possibility of replacing the SMPET with its dual-metallized analogue (DMPET) and determine the effect of increasing the optical density (OD) on the adherence and protection level. Metallized films with OD varying from 2.2 to 4.8 were laminated with glass fabrics of twill, satin and plain weave pattern using a silicone adhesive. The peel adhesion strength of laminates prepared using DMPET was found to be higher (1.01 ± 0.03 N/mm), as compared to SMPET (0.63 ± 0.03 N/mm) and the resulting films did not undergo delamination during flexing. Laminates prepared from satin woven glass fabric exhibited lowest flexural rigidity followed by twill and plain woven glass fabric. Protection offered by the laminate from convective heat was quantified in terms of the thermal protective performance (TPP), and the abraded laminate prepared using DMPET (OD-4.8) was found to meet all the mandatory requirements of proximity clothing, offering an RPP of 27 s and a TPP of 62 cal/cm² s. In comparison, SMPET laminates exhibited lower level of adhesion and offered an RPP of only 7.5 s.

Combustible and noncombustible notions have evolved with time, along with the associated fire tests by which legislation classifies building materials. New Zealand, Japan, and Europe are just some of the many legislations that have followed this evolution, except for North American regulations, which remain attached to methods dating back to 1944. To better understand this stagnation in North American practices, this document first traces the evolution of Canadian regulations on fire classification of materials. Then, a parallel is drawn with the evolution of reaction to fire tests mandated in the National Building Code of Canada. Finally, this paper will review the current fire classification of materials concerning the combustibility concept based on the Steiner tunnel test and the flame spread rating criteria. The analysis reveals that the relevance of the test and its results are questionable, and the reciprocity between test measurement and its classification does not always coincide. Despite the revisions made through time, the classification of materials based on their fire properties remains distinctly binary.