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Surface ignition temperature has been widely used as an ignition criterion for the piloted ignition of common combustible solids. However, experimental observations have shown that the surface temperature of a solid at ignition varies with external heat flux. In addition, if the external heat flux is smaller than the critical heat flux for ignition, the solid will not ignite while the actual surface temperature may be higher than the defined surface ignition temperature. To overcome these limitations and maintain the simplicity of the surface ignition temperature criterion, a new ignition criterion integrating heating rate and surface temperature is proposed, developed, and validated. Predictions based on the new criterion compare well with experimental results on piloted ignition of a thermoplastic material (black PMMA), a thermoset composite material (E‐glass fiber reinforced polyester composite) and a cellulosic material (Red Oak) subjected to different heat flux levels. Potential factors affecting the accuracy and predictive capability of the new heating rate‐related ignition temperature criterion are discussed. The method and associated procedures to construct the heating rate‐related temperature ignition criterion can be used to obtain the same ignition criterion for other combustible solids. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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The piloted transition from smoldering to flaming, though a significant fire safety concern, has not been previously extensively studied. Experimental results are presented on the piloted transition from smoldering to flaming in non‐fire retarded (NFR) polyurethane foam and the fire retarded polyurethane foam Pyrell®. The samples are small blocks, vertically placed in the wall of an upward wind tunnel. The free surface is exposed to an oxidizer flow and a radiant heat flux. The smolder product gases pass upwards through a pilot. The experiments on NFR foam show that the smolder velocity and peak smolder temperature, which increase with the oxygen concentration and heat flux, are strongly correlated to the transition to flaming event, in that there are minimum values of these parameters for transition to occur. The existence of a minimum smolder velocity for ignition supports the concept of a gaseous mixture reaching a lean flammability limit as the criterion for the transition to flaming. To compensate for the solid‐ and gas‐phase effects of the fire retardants on the piloted transition in Pyrell, it was necessary to increase the oxygen concentration and the power supplied to the smolder igniter and the pilot. The piloted transition is observed in oxygen concentrations above 17% in NFR foam and above 23% in Pyrell. The results show that although Pyrell is less flammable than NFR foam, it is still susceptible to smoldering and the piloted transition to flaming in oxygen‐enriched environments, which is of interest for special applications such as future space missions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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The conditions required to cause ignition of solid wood materials under short‐term heating are examined, and it is found that the appropriate ignition temperature applicable under these conditions is 250°C. It is then shown that ignition requirements are different if long‐term heating is involved and that ignition can occur at exposure temperatures much lower than the ignition temperature pertinent to short‐term heating. It is shown that hot surfaces of 77 °C or higher, if located for a long duration next to a wood member are liable to lead to its ignition in a self‐heating mode. Recommendation is made that prudent practices for design or installation must also involve a suitable safety factor. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Self‐ignition of deposited combustibles is a possible reason for excessive fires occurring on deposits for recycling materials or on waste dumps. Two series of experiments were performed to assess the hazard of self‐ignition: hot storage tests with different homogeneous mixtures of combustible material and inert material and tests with pockets of combustible material embedded in inert matter. In the first test series considerable exothermicity (ΔT>60K) was observed for mass fractions of combustible material as low as 2.5%. In the second series it could be shown that the heat transfer from a pocket of burning material through the inert matter can ignite a second pocket of combustible matter. Based on the experimental data, numerical simulations were performed to predict self‐ignition on real‐scale waste deposits. For a deposit of specific size and shape, the influence of the ambient temperature on the occurrence of self‐ignition has been investigated. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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The ignition characteristics of combustible solids are affected by many factors such as material properties, external heating source, and surrounding environmental conditions. In practice, these factors can vary significantly from one application to another. Thus, it is important to evaluate the sensitivity and uncertainty aspects of the effect of these factors on ignition. This study attempts to achieve this goal through sensitivity and uncertainty analyses on the piloted ignition of fiber‐reinforced polymer (FRP) composite panels. A Monte Carlo simulation using the Latin hypercube sampling method was employed to conduct sensitivity and uncertainty analyses. An integral model combining a general thermal thickness model with a heating rate‐related ignition temperature criterion was used as the ignition prediction model. Time‐to‐ignition was evaluated as the output parameter against the variations of input parameters such as material properties, external heating source, and surrounding environmental conditions. In addition, to identifying important sensitivity factors and uncertainty ranges of piloted ignition, a critical thermal thickness was found for the composite panels. These findings can serve as guides for the fire safety design of FRP composite materials for various applications. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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The transition from smoldering to flaming was studied on fabric, batting, and foam assemblies via an electric spot ignition source of similar intensity to a cigarette. The materials studied included four different fabrics (cotton, polyester, cotton/polyester blend, flame retardant cotton/polyester blend), two types of batting (cotton, polyester), and three types of polyurethane foam (nonflame retardant, flame retardant by FMVSS 302 testing, flame retardant by BS5852 testing). The results from testing found that materials highly prone to smoldering could propagate smoldering into foams and lead to ignition, whereas materials that tended to melt back from the ignition source did not. Flame retardant fabrics or foam can and do prevent the transition from smoldering to flaming provided sufficient levels of flame retardants are incorporated in the upholstery fabric or foam. The transition from smoldering to flaming of cotton fabric/nonflame retardant foam assembly was also studied using temperature measurements and evolved gas analysis. It was determined that the transition takes place when the oxygen consumption by accelerating smoldering front exceeds the oxygen supply. At this point, the solid fuel gasification becomes driven by thermal decomposition rather than by surface oxidation which leads to high enough concentrations of fuel for flaming combustion to occur. 相似文献
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使用锥形量热仪研究了聚合物材料PMMA(Poly(methyl methacrylate))在不同热通量下的强制点燃,得到其相应的点燃时间和临界表面温度。同时考虑到强制点燃过程中气、固相的能量和质量传递及化学动力学过程,给出了一种描述聚合物材料强制点燃的气相和固相数学模型,并对实验结果进行了计算,同时与文献数据进行了比较,其计算结果与实验值吻合较好。 相似文献
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Craig Beyler 《火与材料》2006,30(3):215-221
Rubbers, including styrene‐butadiene rubber (SBR), are well known to be susceptible to self‐heating. SBR is used in a wide range of applications and is often produced in the form of a crumb which is then used to form the final product. The crumb may be transported and stored in large quantities. Self‐heating properties of a SBR crumb have been determined using standard oven methods. The results indicate that self‐heating is a real hazard for SBR crumb. The results are generally consistent with recent measurements by Clothier and Prichard (Combust. Flame 2003; 133 :207–210) for rubber tyre crumb. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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董洁;刘博;杨燕飞;南雪丽;张俊平 《化工进展》2025,44(3):1445-1453
氧化剂材料在工业炸药、导弹以及固体推进剂等领域应用广泛;对工业社会的重要性不言而喻。然而;由于这些氧化剂材料具有高极性表面和特殊结构;因此这些材料极易吸湿;从而严重影响了其在固体推进剂中的性能和可靠性。为满足现代航天和导弹技术对推进剂高性能、高稳定性和高安全性的迫切需求;必须提高氧化剂的性能指标;以满足航天和导弹领域对动力源的严格标准。为此;本文首先介绍了氧化剂材料的分类、结构和化学组成;为后续的归纳概括提供了基础。其次;总结了氧化剂材料防吸湿方面的最新研究进展;进一步探讨了改进其防吸湿性能的方法。最后;通过对氧化剂材料在固体推进剂领域的优势和不足的分析;对氧化剂防吸湿性能研究给出了以下几点建议:深入研究氧化剂材料的分子结构和表面特性;引入纳米技术;开发复合氧化剂材料以及新型的表面涂层技术或封装工艺;综合考虑热稳定性、感度低以及与固体推进剂的其他组分（如黏合剂基体网络）的相容性等因素;着重关注其工业化生产和应用的可行性。这将大幅度提升氧化剂材料的性能;为我国航天和导弹等领域的发展提供保障。 相似文献
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To assess the risk for spontaneous combustion of biomass pellets during storage, it is important to know how prone the fuel is to self‐heating, ie, to determine the reactivity. This article presents the results from isothermal calorimetry tests performed on 31 different biomass pellet batches. The purpose of the tests has been to characterize pellets by measuring the reactivity and investigate how the pellet composition influences the heat release rate (HRR) and thereby the self‐heating potential of pellets. The results from the tests clearly indicate that there is a significant difference in reactivity between different types of pellets. The tested high reactive pellet batches reached maximum specific HRRs (HRRmax) of 0.61 to 1.06 mW/g while pellet batches with low reactivity showed HRRmax of 0.05 to 0.18 mW/g. The tested batches were primarily ranked on the basis of HRRmax, but an alternative ranking based on specific total heat release rate (THR) during the test period was also used for comparison. The test results also indicate that pine/spruce mix pellets are significantly more reactive than all other types of pellets tested and that pellets consisting of 100% pine are more reactive than pellets consisting of 100% spruce. Pellets produced from wine pruning/grape pomace (winery wastes), straw, or eucalyptus are not very reactive compared to pellets consisting of pine/spruce. The results also show that the reactivity of the pellets can be reduced either by introducing certain kinds of antioxidants into the pellets or by extracting lipids from the raw material of pellets. 相似文献
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在醋酸、相转移催化剂聚乙二醇存在下,蒽与硝酸铈铵反应生成10-硝基蒽酮。聚乙二醇作为相转移催化剂,可以提高反应的选择性。最佳反应条件为:n蒽∶n硝酸铈铵为1∶1.05,反应温度50℃,反应时间1.4h。10-硝基蒽酮的产率达74.1%。 相似文献
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The time dependences of electrical conduction and self‐heating behaviors in high‐density polyethylene filled with acetylene carbon black of 0.082 in volume fraction are studied in relation to voltage and ambient temperature. The characteristic decay current constant τi, and the exponential growth time constant for self‐heating τg are determined for the samples under voltages U above the critical value Uc for the onset of self‐heating. The influences of voltage and ambient temperature on τi and τg as well as the amplitude of the low‐resistance to high‐resistance switching are discussed on the basis of the random resistor network (RRN) model and the relationship between Uc and the intrinsic resistivity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1124–1131, 2006 相似文献
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The time dependences of electrical conduction and self‐heating in high‐density polyethylene/acetylene carbon black composites crosslinked with electron beam irradiation at three different dosages are studied in relation to voltage and ambient temperature. The characteristic decay current constant (τi) and the exponential growth time constant for self‐heating (τg) are determined for the samples under voltages (U) above the onset voltage (Uc) of self‐heating. The influence of crosslinking on the current decay dynamics, self‐heating process, and amplitude of the resistance switching under field action are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4418–4422, 2006 相似文献
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在乙腈、聚乙二醇存在下,8-羟基喹哪啶与硝酸铈铵反应生成标题化合物。8-羟基喹哪啶与硝酸铈铵的物质的量比为1∶1.4时,加热回流反应1.8 h,5,7-二硝基-8-羟基喹哪啶的产率可达78.3%。 相似文献
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A green polymer self‐etching strategy for fabricating superhydrophobic surfaces exhibiting low and high adhesion is proposed by using hot‐pressing and exfoliation on a pair of low density polyethylene (LDPE) films. It is demonstrated that the hot‐pressing temperature has significant influence on the surface morphology of LDPE. Effective hot‐pressing temperature for low‐adhesive superhydrophobicity ranges from 109 to 161 °C. Bird's‐nest like micro‐/nanostructures are observed in the unzipped LDPE surfaces compressed at 109 °C, which shows excellent water repellency. LDPE surface compressed at 108 °C demonstrates superhydrophobicity with high adhesion, i.e., a water droplet cannot roll off even when the surface is turned upside down. Furthermore, superhydrophobic vessels are processed and applied to transport water and microdroplets of water losslessly.
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Allal Challioui Daniel Derouet Abdelkader Oulmidi Jean Claude Brosse 《Polymer International》2004,53(8):1052-1059
Alkoxylation of epoxidized polyisoprene catalyzed by cerium ammonium nitrate (CAN) was achieved under very mild conditions both in melt and in solution. The cleavage of the epoxidized units with alcohols leads to the formation of alkoxyalcohol units and epoxide rearrangement units in the case of 20 and 38 % epoxidized 1,4‐polyisoprenes. For higher percentage of epoxidation (72 %), cyclization of epoxidized units is observed, which dramatically reduces the alcohol grafting percentage onto the polymer chains. The glass transition temperature increase with the percentage of alkoxylation is attributed to both alkoxy and hydroxyl groups formed after the ring opening of the epoxidized units. However, size‐exclusion chromatography analysis of the modified polymers showed a decrease in the number‐average molecular weight and an increase in the weight‐average molecular weight, which can be interpreted as the degradation and crosslinking of the polymer chains, respectively. Copyright © 2004 Society of Chemical Industry 相似文献