Fire and Materials最新文献

The objective of the study was to alleviate the thermal-moisture comfort (TMC) of phase change material (PCM) thermal protective clothing, while simultaneously enhancing thermal protective performance (TPP) by a drip molding process. Nine types of PCM dripped fabrics were prepared by the drip molding process and served as comfort layers of thermal protective clothing. The TMC and TPP of the fabric systems were measured. A new method was proposed to balance the TMC and TPP of thermal protective clothing. The results demonstrated that the drip molding process marginally weakened the TMC while substantially enhancing the TPP of fabric systems. But the TMCs of the PCM dripped fabrics were far larger than the PCM coated fabric. Specifically, an increase in droplet diameter led to a decline in TMC and an improvement in TPP, whereas an increase in droplet interval resulted in an enhancement in TMC and a decrease in TPP. The findings obtained in this study can be used to engineer fabric systems that provide better protection for heat stress and skin burns.

In order to improve the dispersibility of inorganic fillers and enhance its ceramifiable flame-retardant efficiency, the ceramifiable flame-retardant silicone rubber composites were prepared using glass powder, zinc borate, ammonium polyphosphate, mica powder, platinum catalyst as ceramifiable flame-retardant agent, and various silane coupling agents as interfacial modifier. The micromorphology, mechanical properties, flame retardancy, thermal stability, and combustion behavior of ceramifiable flame-retardant silicone rubber composites, as well as the flexural strength of the corresponding ceramics generated after pyrolysis of the composites were examined. The results reveal that the inclusion of silane coupling agents improves the dispersibility of ceramifiable flame-retardant agents substantially. The mechanical properties, flame retardancy, thermal stability, and combustion behavior of ceramifiable flame-retardant silicone rubber composites are all improved. When compared to a composite without a silane coupling agent, the tensile strength of the composite can be improved by up to 1.9 times. Only 0.5phr silane coupling agent is required to raise the vertical combustion rating from V-1 to V-0, and the composite with 3 phr KH570 has a LOI value of 38.6. Meanwhile, the heat release rate of the composite is reduced to a certain extent, and the time to ignition and residue are dramatically enhanced after the addition of silane coupling agent in the cone calorimetry test. Moreover, flexural strength of the corresponding ceramics generated after pyrolysis of the composites rapidly increases with increasing silane coupling agent content, which can reach to 24.7 MPa with addition of 3 phr KH570.

This work explores the elaboration of wood particle-based composites incorporating bio-based phase change materials, with epoxidized linseed oil or clay as a binder. Fire performance evaluation of the novel composites includes an assessment to determine the impact of the addition of boric acid as a fire retardant, as well as the incorporation of recycled paper fibres containing boric acid, and the application of trimethoxymethylsilane coating. The study employs thermogravimetric analysis and cone calorimetry under uniform external irradiance, with a T-history method to analyse thermal behaviour. Results indicated that fire retardants do not compromise the energy functionality of bio-based phase change material composites, exhibiting a latent heat of approximately 50 J/g. The density ranges from 750 to 875 kg/m³. The use of clay as a binder improves fire performance, leading to a 60% decrease in total heat release and 52% of the composite mass remaining after analysis. Although enhancing fire performance presents challenges, incorporating wood particles in clay demonstrates a promising potential approach for safe use in building applications, contributing to energy efficiency in indoor heating and cooling. The findings contribute valuable insights into these materials for creating safer and more efficient building solutions, particularly in terms of thermal regulation and fire safety.

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.