Temperature distribution of steel columns protected by sprayed fire retardant coatings with three sides exposed to fire

Temperature gradient will occur when the steel framed column is heated from three sides in a fire. Current design codes provide the design equations to calculate the temperature elevation of the steel column unevenly heated in a fire. However, the design equation is based on the assumption that the temperature is uniformly distributed across the section. The temperature field of a steel column protected by sprayed fire retardant coating with three sided exposed to fire is analyzed using a verified finite element model. Parameters that affect the temperature distribution across the section are investigated, which include the section height, the web thickness, and the fire protection thickness. The coded equations based on the element factor approach are modified according to the finite element simulation results. Different temperature distribution profiles are proposed through using the heated flange temperature, the web temperature, and the protected flange temperature. Copyright © 2014 John Wiley & Sons, Ltd.     

膨胀型防火涂料的研究进展

介绍膨胀型防火涂料的机理和影响其性能的主要因素以及国内外膨胀型防火涂料的研究状况。     

Influences of flame-retardant fillers on fire protection and mechanical properties of intumescent coatings

A combination of acrylic binder and flame-retardant ingredients was used to synthesize the solvent-borne intumescent coatings designed for steel substrates. The influences of individual and various combinations of flame-retardant fillers on the fire protection and mechanical properties of the coatings were characterized by using Bunsen burner, thermogravimetric analysis, limiting oxygen index, field emission scanning electron microscopy, freeze–thaw cycles, static immersion and pull-off type equipment. It was found that the combination of aluminium hydroxide (Al(OH)₃) and titanium dioxide (TiO₂) has significantly improved the fire protection, thermal stability and water resistance of the coating. This formulation had an LOI value of 34, which indicated good flammability resistance of the coating. The adhesion strength tests showed that the coating added with magnesium hydroxide (Mg(OH)₂) exhibited maximum bonding strength to the metal surface due to its effective interface adhesion. Hence, the findings from this study revealed that the selection of appropriate combinations of flame-retardant fillers strongly influenced the physical and chemical properties of the coatings.     

Laboratory and gas-fired furnace performance tests of epoxy primers for intumescent coatings

Protection of steel structures, using so-called intumescent coatings, is an efficient and space saving way to prolong the time before a building, with load bearing steel constructions, collapses in the event of a fire. In addition to the intumescent coating, application of a primer may be required, either to ensure adhesion of the intumescent coating to the steel or to provide corrosion resistance. It is essential to document the performance of the intumescent coating together with the primer to ensure the overall quality of coating system. In the present work, two epoxy primers were used to investigate the potential failure mechanism of a primer applied prior to an intumescent coating. The analysis was carried out using; (1) gas-fired test furnace, (2) a specially designed electrically heated oven, and (3) thermo gravimetric analysis. When tested below an acrylic intumescent coating, exposed to a gas-fired furnace following the ISO834 fire curve (a so-called cellulosic fire), one of the primers selected performed well and the other poorly. From tests in the electrically heated oven, it was found that both primers were sensitive to the film thickness employed and the presence of oxygen. At oxygen-rich conditions, higher primer thicknesses gave weaker performance. In addition, a color change from red to black was observed in nitrogen, while the color remained red in the oxygen–nitrogen mixture. In summary, the results suggest that an adequate choice of primer, primer thickness, and intumescent coating is essential for a good performance of an intumescent coating system.     

Experimental determination of fire heat release rate with OC and CDG calorimetry for ventilated compartments fire scenario

This research deals with the experimental determination of the heat release rate (HRR) of fires in mechanically ventilated compartments based on oxygen consumption (OC) and carbon dioxide generation (CDG) calorimetry. It proposes formulations for fire in force‐ventilated compartments on the same basis as the relations established for hood calorimetry in an open atmosphere but considering inertia and unsteady behavior of the fire via the time variation mass of O₂ and CO₂ in the compartment. The value of the new formulations of HRR has been tested in two series of propane gas fire experiments performed in a large‐scale facility. The first series involves a fire scenario with one compartment, and the second series, a fire scenario with three compartments connected to each other by doorways. In the first test series, the OC and CDG formulations for HRR are assessed. In the second test series, the OC and CDG formulations are presented with two approaches to definition of the control volume: approach involving three rooms and the flow rate in the ventilation network and approach involving only the fire room and the flow rate through the doorways. On the basis of the fire experiments considered, the most accurate method (accuracy to within 10%) for determining the HRR is the CDG formulation with approach for the control volume without considering the flow rates at the doorways. This analysis points out the different features of each method (OC and CDG) and thoroughly discusses their advantages and drawbacks. The overall analysis allows guidelines to be formulated for fire HRR calculation in confined and ventilated compartments. Copyright © 2013 John Wiley & Sons, Ltd.     

脲醛树脂石蜡微胶囊的制备及其在保温隔热涂料中的应用

以脲醛树脂为壳材料,质量比为1:1:1的液体石蜡、十八烷和固体石蜡组成的混合物为芯材,用原位聚合的方法制备了脲醛树脂石蜡微胶囊,采用红外光谱分析和扫描电子显微镜对微胶囊进行了表征,使用差示扫描量热仪(DSC)研究了石蜡微胶囊的热性能及相变温度。将该微胶囊制成保温隔热涂料,测定了涂料的保温隔热效果及其机械性能。结果显示,脲醛树脂成功包覆了石蜡,微胶囊表面粗糙,粒径为10μm左右,其相变温度分别为2.1°C、15.1°C和42.9°C,相变焓为50.1J/g。与仅含钛白粉的空白涂料相比,添加了空心玻璃微珠、改性硅藻土和脲醛树脂石蜡微胶囊制备的保温隔热涂料最大温差11.5°C,平均温差9.7°C,涂层的机械性能符合国标要求。     

Influence of external heat flux and coating thickness on the thermal insulation properties of two different intumescent coatings using cone calorimeter and numerical analysis

Polymeric intumescent coatings are fire protective materials that increase their thermal resistance when exposed to high temperatures to prevent building structures from damage. The idea of the investigation was to develop a simple test method to determine the time dependent thermal conductivity of intumescent coatings. Therefore steel plates were coated with two different intumescent systems. During cone calorimeter tests the temperature at the back side of the coated plates was measured. These results were used to calculate the time dependent thermal resistance of the protective layer with the simulation program IOPT2D for different external heat fluxes and different layer thickness. Copyright © 2003 John Wiley & Sons, Ltd.     

Effects of natural weathering on the fire properties of intumescent fire‐retardant coatings

Fire‐retardant coatings could be one option for providing enhanced protection to buildings during a wildfire, particularly when applied to combustible siding and in under‐eave areas. Limited studies have been conducted on their effectiveness but maintaining adequate performance after weathering has been questioned. This paper reports on a study evaluating the effect of natural weathering on the performance of intumescent‐type fire‐retardant coatings. The main concerns were (a) the reduction of ignition resistance of the coating after weathering and (b) the coating might contribute as a combustible fuel and assist the fire growth after weathering. This study evaluated the performance of 3 intumescent coatings that were exposed to natural weathering conditions for up to 12 months. A bench‐scale evaluation using a cone calorimeter was used to evaluate the performance of the coatings at 3 heat flux levels (30, 50, and 70 kW/m²). Our results showed that weathering exposure reduced the effectiveness of fire protection of intumescent coatings, but the weathered coatings did not act as additional fuels. Weathering orientation showed much less effect on the performance of intumescent coatings in comparison to other parameters. There was statistical evidence that weathering duration, heat flux level, and coating type affected the combustion properties.     

Effects of inorganic fillers on the shear viscosity and fire retardant performance of waterborne intumescent coatings

In the present work, the effects of inorganic fillers on the fire retardant performance of waterborne intumescent coatings are investigated by thermogravimetry (TG), capillary rheometer, X-ray diffraction spectroscopy (XRD) and fire retardant test, etc. The TG results indicate that the thermal stability of vinyl acetate-vinyl ester of versatic acid copolymer (hereafter VAc-VeoVa) in VAc-VeoVa/Si–Al powder composite or in VAc-VeoVa/Halloysite nanometer-tube (HNTs) composite is improved mainly due to the release of the crystal water in Si–Al powder or HNTs. Capillary rheometer analysis results demonstrate that the VAc-VeoVa/HNTs composite melt possesses the highest shear viscosity, because of the large specific surface area of HNTs and the strong interaction force between HNTs and VAc-VeoVa. Weight loss difference (ΔT) of filler/ammonium polyphosphate (APP) composites show antagonism effects at 300 °C < T < 650 °C and synergistic effects at T > 650 °C. The fire retardant test results show the coatings using TiO₂/Si–Al powder/HNTs (8/1/1) as multiple fillers obtains an intumescent char layer with intumescent ratio of 28.14 and presents excellent fire retardant performance (3327 s). It is found that the high melt viscosity, resulted from the effect of inorganic filler, immobilizes the relaxation and rotation of polymer chain, restricts the intumescent behavior of the coatings, which leads to the formation of an intumescent char layer with lower intumescent ratio and the shortening of the fire retardant time. Moreover, the antagonism effect between filler and APP reduces the catalytic dehydration efficiency of pentaerythritol (PER) and VAc-VeoVa, which, as a result, also affects the final fire retardant performance of coatings.     

Testing fire protective properties of intumescent coatings by in-line temperature measurements on a cone calorimeter

An experimental setup was proposed for evaluating the thermal shielding efficiency of intumescent coatings. In particular, a cone calorimeter as heater source was coupled with a thermocouple as detector of the temperature of steel plates coated with intumescent coatings. According to ENV 13381-4 test procedure, the heating curves of the setup was measured by plate thermocouple and compared with ISO 834 standard curve. Meanwhile, the comparison was also made between temperature profiles of blank steel plates at different heat fluxes and unprotected steel elements under ISO fire. The possible correlation between bench scale and large scale test was hence discussed. Several factors (heat flux, distance to cone heater, coating thickness, sample size, edge effect and heat insulator) were deeply investigated and discussed: significant relationships between these parameters and the thermal protective properties of the intumescent coating were evidenced; furthermore a fully developed intumescent char could be obtained by controlling the aforementioned parameters. As a conclusion, the proposed bench-scale test was found to be comparable to the large scale test only in the early heating stages.     

复合型反射隔热涂料的制备与性能研究

采用红外高反射率的空心玻璃珠(BLZ)和彩色空心陶瓷珠(TCZ)制备得到复合型建筑反射隔热涂料,研究了功能性填料、乳液、颜填料及颜填料粒径配比对涂料隔热效果及耐沾污性能的影响。试验结果表明,成膜物质种类的差异对涂料隔热性能的影响较小,当纯丙乳液含量为40%时,隔热温差为14.6℃;二氧化钛能有效提高涂层反射隔热性能,采用20%的二氧化钛添加量能使隔热温差达到15℃左右;填料含量为12%时,具有良好的隔热增强效果,隔热温差为14.6℃;当m(BLZ)/m(TCZ)=1:1时,涂层隔热温差为16.5℃;耐沾污测试表明,当采用纯丙乳液,钛白、硅藻土和滑石粉比例为5:1:1,m(BLZ)/m(TCZ)=2:1时,具有良好的耐沾污性能。     

Comparative study of the fire protection performance and thermal stability of intumescent fire-retardant coatings filled with three types of clay nano-fillers

The fire protection and thermal stability properties of intumescent fire-retardant coatings filled with three various clay nano-fillers (layer double hydroxide [LDH], montmorillonite [MMT], and sepiolite) were compared by fire protection tests and thermo-gravimetric analysis. The fire protection tests show that the incorporation of three fillers improves the fire protection properties of the intumescent fire-retardant coatings and the addition of 1 wt% sepiolite exhibits the lowest flame spread rating of 9.9 and equilibrium backside temperature of 164.5°C at 900 seconds. TG analysis shows that the incorporation of nano-fillers imparts a considerable enhancement of thermal stability and char formation to the intumescent coatings. Especially, the coating with 1 wt% sepiolite acquires the highest residual weight of 34.2% among the samples. Char residue analysis presents that the introduction of clay nano-fillers plays a positive role in enhancing the compactness and anti-oxidation ability of the char residues, and this positive effect as well as the flame-retardant efficiency depends on the types of clay nano-fillers. The three types of layered clay nano-fillers exhibit synergistic flame-retardant effectiveness in the order of sepiolite > MMT > LDH.     

Effect of heat treatment on microstructure and mechanical properties of cold sprayed Ti coatings with relatively large powder particles

In this study, the effect of post-spray heat treatment on the microstructure, microhardness, and adhesive strength of the cold-sprayed Ti coating was investigated. It was found that a thick and relatively porous Ti coating was deposited by cold spraying. The coating surface layer presented a more porous structure. The microhardness of the as-sprayed Ti coating was slightly higher compared to pure Ti bulk, owing to the work hardening effect during deposition. After annealing at 850°C for 4 h under vacuum condition, the Ti coating also presented a porous structure with more uniformly distributed small pores. A metallurgical bonding between the deposited particles was formed through annealing treatment. The adhesive strength of coating was significantly improved after annealing. The microhardness of the annealed Ti coating was also increased.     

掺杂SnO_2纳米导电氧化物在透明隔热涂料中的应用及前景

介绍了掺杂SnO2纳米导电氧化物TCO浆料的制备及在透明隔热涂料中的应用。     

A mechanistic study of the fire performance of the silica and zinc borate nanoparticles-incorporated intumescent coatings based on epoxy resin

An epoxy-based intumescent coating containing the silica and zinc borate nanoparticles was fabricated. The fire performance of the coating with the optimum formulation was investigated in terms of the changes in the physical and chemical structure of the formed char layer during the exposure to a temperature of 1000°C. The state of the chemical structure was analyzed by performing the Fourier-transform infrared spectroscopy, x-ray diffraction, and x-ray photoelectron spectroscopy analysis from the char layer at the three-time intervals of 10, 30, and 60 min of the heating process. The innovative Condorcet method was also employed to examine the changes in the physical structure of the formed char layer. Some instabilities were detected in the physical structure of the char layer in the middle period of heating. Moreover, a gradual formation of silicon carbide crystalline structure was observed on top of the surface, followed by its oxidation to silica over time. In contrast, in the bulk structure, silicon crystalline structures (Coesite) intensified with time. Boron nitride was also increasingly created on the top surface and in the bulk of the coating over the heating time. These findings proved the effective role of the silica and zinc-borate nanoparticles in the fire performance of epoxy-based intumescent coatings.     

Resistance to fire of intumescent silicone based coating: The role of organoclay

The fire performance of a curable-silicone based coatings containing expandable graphite (EG) and an organoclay is evaluated in hydrocarbon fire scenario (standard UL1709) using a lab-scale furnace test. It is shown that the use of organoclay allows achieving better performance. The influence of the clay as additional filler is investigated on the fire performance and on the mechanical properties of the char. It is shown that the clay increases significantly the mechanical properties of the char and hence, the fire performance of the silicone based coating. In a next part, the silicone/clay material was characterized by electron microscopy, wide-angle X-ray scattering and solid state ²⁹Si nuclear magnetic resonance (NMR). It evidences the nanodispersion of the clay into the silicone matrix and two main interactions: (i) intercalation of some silicate layers and (ii) chemical reactions between the hydroxyl groups of the clay and the silicone matrix. Finally, X-ray fluorescence of the residue after fire testing shows the organoclay is present uniformly throughout the thickness of the char, due to the previous interaction, and hence increasing the cohesion of the char.     

Thermal analysis of plasma sprayed oxide coatings sealed with aluminium phosphate

Thermal analysis by thermogravimetry and differential scanning calorimetry was carried out for plasma-sprayed alumina and chromia coatings to study their stability after plasma spraying and for aluminum phosphate sealant to study phosphate reactions during the sealing heat treatment. Thermogravimetric analysis for alumina coating did not show any change in the coating due to the heat treatment, though the phase structure had changed from metastable γ-Al₂O₃ to stable α-Al₂O₃. In the chromia coating thermogravimetric analysis showed 1.7 wt.% weight increase due to the oxidation of the sprayed coating. During plasma-spray process the chromia coating had gained some under-stoichiometry or some of the chromia had decomposed into metallic chromium or other oxides. Thermal analysis for aluminum phosphate sealant showed weight loss of about 27 wt.%. This corresponds well to the formation of metaphosphates via dehydration of aluminum phosphate solution during the sealing heat treatment. Thermal analysis for the mixture of sealant and alumina coating showed slightly different behaviour than plain sealant. The sealant reacted with the alumina coating forming a crystalline phase, berlinite-type orthophosphate AlPO₄. Thermal analysis for the mixture of sealant and chromia coating showed nearly similar behaviour than plain sealant and no indications of the chemical reactions were detected.     

Reaction of aerogel containing ceramic fibre insulation to fire exposure

Aerogel containing ceramic fibre insulations represent a newly developed high performance insulation material applied in industrial installations and recently expanding rapidly into the construction industry to reduce the heat transfer through walls and ceilings. As a rather expensive material they are preferentially used in cases where slim layers of insulation are needed mainly in refurbishing of existing buildings especially those under heritage protection. The reaction to elevated temperatures in case of fire is a decisive property for building applications. The present article investigates the reaction to fire of an aerogel containing ceramic fibre insulation already available on the market. This reaction was monitored experimentally by means of temperature sensors at different depth in the material when subjected to the standard ISO fire. The measured temperature evolutions are discussed with respect to radiative heat transfer in an optically thick medium, temperature induced changes in density because of mass loss and the occurrence of endothermic and exothermic reactions detected by thermal analysis and compared with simulation results. Copyright © 2016 John Wiley & Sons, Ltd.