Material fire properties and predictions for thermoplastics

Ignition and burning rate data are developed for nylon 6/6, polyethylene, polypropylene and black polycast PMMA in a cone calorimeter heating assembly. The objective is to examine a testing protocol that leads to the prediction of ignition and burning rate for thermoplastics from cone calorimeter data. The procedure consists of determining material properties, i.e. thermal inertia, specific heat, thermal conductivity, ignition temperature, heat of gasification and flame heat flux from cone data, and utilizing these properties in a model to predict the time to ignition and transient burning rate. The procedure is based on the incident flame heat flux being constant in the cone calorimeter which occurs for flames above the top of the cone heater. A constant net flame heat flux of approximately 20 kW/m² for nylon 6/6, 19 kW/m² for polyethylene, 11 kW/mP² for polypropylene and 28 kW/m² for black PMMA is obtained for irradiation levels ranging from 0 to 90 kW/m². The burning rate model is shown to yield good accuracy in comparison to measured transient burning in the cone assembly.     

Analysis of principal gas products during combustion of polyether polyurethane foam at different irradiance levels

This paper studies the release of the principal gas species produced during the combustion of a non-flame-retarded Polyether Polyurethane Foam (PPUF) of density of 20.9 kg m⁻³ in the cone calorimeter. Five irradiance levels are studied: 10, 20, 30, 40 and 50 kW m⁻². Heat release rate, mass-loss rate and bulk gas mass flow are measured. The mass flow and yields of gas species are measured as well. The analysis of release of gas species relative to time allowed the study of the different stages of PPUF kinetics and to quantify the gas composition. Of the twenty-two different gas species that were monitored simultaneously, the principal species found were CO₂, CO, H₂O, NO and total hydrocarbons. According to species release, two decomposition stages for PPUF are identified. In the first stage, the solid structure breaks down carrying the decomposition of isocyanate, and in the second stage the polyol decomposes. These two stages are in agreement with the decomposition mechanism proposed in the literature. However, the data presented here is the first experimental study of burning behavior of PPUF taking into account the release of gas species too. An elemental analysis was performed and the chemical formula of the virgin material was determined. This allows the mass balance of the elements in the virgin foam content with the gaseous product content. The effective heat of combustion and the ratio between heat release rate and CO₂ mass flow are calculated at each of the irradiance levels.     

铺层结构对碳纤维/环氧层压板火反应特性的影响

利用锥形量热仪,垂直/水平燃烧速度测试仪、极限氧指数测定仪研究了单向、织物两种铺层结构对碳纤维/环氧层压板火反应特性的影响.结果表明,随热辐射强度的增加,不同铺层结构碳纤维/环氧层压板的点燃时间均缩短,质量剩余率降低,热释放速率、产烟速率峰值均增加,达到峰值时间变短,总热释放量和总烟释放量增加;在相同热辐射强度下,相比...     

Evaluating Models for Predicting Full-Scale Fire Behaviour of Polyurethane Foam Using Cone Calorimeter Data

Two models that can be used to predict full-scale heat release rates of polyurethane foam slabs were evaluated in this study. Predictions were compared with results of furniture calorimeter tests of 10 cm thick polyurethane foam specimens which were ignited in the centre or on the edge. Furniture calorimeter results indicated that peak heat release rates and fire growth rates were higher during centre ignition tests than edge ignition tests. For both situations, the growth phase of the heat release rate curves measured in the full-scale tests was successfully predicted using t ² design fires; the choice of a specific t ² fire depended on the surface area of the specimen and ignition location. A model originally developed during the European Combustion Behaviour of Upholstered Furniture (CBUF) project was also evaluated using heat release rate data from cone calorimeter tests and flame area burning rates measured using infrared video records of the furniture calorimeter tests. This model was able to successfully predict the initial growth phase of the fires and predictions of peak heat release rates were within 17% of measured values. The model had less success in predicting heat release rates later in the growth phase and during the decay phase of the fires, and did not appear to capture all of the physics of the full-scale tests, in particular foam melting and subsequent liquid pool burning. As the model did show promise, future work is planned to address these shortcomings and to develop improved flame spread models for polyurethane foam.     

Burning rate and flame heat flux for PMMA in a cone calorimeter

Ignition and burning rate data are developed for thick (25 mm) black Polycast PMMA in a cone calorimeter heating assembly. The objective is to establish a testing protocol that will lead to the prediction of ignition and burning rate from cone data. This is done for a thermoplastic like PMMA. The incident flame heat flux, for irradiation levels of 0–75 kW/m², is found to be approximately 37 kW/m² for black PMMA. Its constancy is shown due to the geometry of the cone flame. Also, this flame is shown to be nearly transparent for cone irradiance (>90%). The heat of gasification of the black PMMA used is found to be approximately 2.8 kJ/g; higher than values reported for other PMMA samples. This is believed to be due to differences in molecular structure or pigmentation of the PMMA tested. A burning rate model is demonstrated to yield good accuracy in comparison to measured transient values. An exact solution is found for constant heat flux conditions.     

Analytical and experimental study on multiple fire sources in a kitchen

Experiments were carried out earlier in a room calorimeter to study cooking oil kitchen fires with multiple fire sources under natural ventilation with burning characteristics observed. Air and fire temperatures inside the room and heat release rates were measured before. In this paper, average heat release rate, burning time and average oil mass flux were investigated by analytical studies together with those experiments. Average heat release rate, burning time and average oil mass loss rate for 2 woks, 4 woks and 6 woks were compared. Three typical burning conditions were identified and analyzed. Rapid burning rate in the experiments was observed. A mathematical model on heat transfer from the flame to the pan surfaces was developed. Analytical results were justified by the earlier experimental observations. This would compare the results better with 2 woks, 4 woks and 6 woks. In the calorimeter, each pan was placed at different distances away from the door. The burning process, mass loss rate of kitchen oil and burning time are different. Therefore, only the average values were used to get more reasonable results.     

基于CONE的超高温耐火电缆火灾危险性分析

利用锥形量热仪对超高温耐火电缆在不同辐射功率下的点燃时间（TTI）、热释放速率（HRR）、质量损失速率（MLR）和燃烧残余物进行了研究。研究表明,随着辐射功率增加,耐火电缆的TTI逐渐缩短,HRR和MLR逐渐增大,火灾危险性逐渐增加。超高温耐火电缆在35 kW/m2和50 kW/m2辐射功率下火灾性能指数相比于25 kW/m2分别增加了44.4%和176.5%,火灾增长指数分别增加了30.4%和83.0%。结合理论分析可以得出,耐火电缆的临界辐射功率为3.61 kW/m2、零辐射平均热释放速率为36.5 kW/m2,表现出较低的火灾危险性。     

Combustibility Parameters for Enclosure Lining Materials Obtained During Surface Flame Spread Using a Reduced Scale Ignition and Flame Spread Technique

A reduced scale ignition and flame spread technique, RIFT, was implemented in the cone calorimeter system to obtain thermocombustibility properties of enclosure lining materials during flame spread over the sample surface. Previously, a thermal model of ignition and opposed flow flame spread was used to analyze flame spread data obtained using RIFT. Here, a framework is discussed for deducing critical material combustibility parameters from the measured heat release and mass loss rates as the spreading flame proceeds to the point of flame extinction. The nature of the data and analytical framework allows users to deduce spreading flame flux from the heat release rate (HRR) and mass loss rate (MLR) data relatively economically and directly. The anomalies highlighted by comparing flame spread data in the RIFT system compared to data from the BS 476 Part 7 apparatus indicates that the RIFT system is well-suited for developing and refining models describing ignition, flame spread, and mass burning.     

An experimental study of the thermal performance of a novel intumescent fire protection coating

The thermal performance of a novel intumescent coating was investigated at a laboratory scale. A combination of small and large-scale tests was performed in order to fully understand the behavior of the coating. For small-scale testing, experiments were conducted using thermogravimetric analyses. These experiments were run at several heating rates in a nitrogen atmosphere. The results showed that the thermal degradation of the coating occurred in different stages, and, the main mass loss took place around 300 °C. Furthermore, the current work showed that oxygen doesn't exert any significant effect during the early stages of degradation of the materials; however, its interference can be noted past the attainment of the peak value for mass loss rate curve.For large-scale testing, the experiments were carried out in a cone calorimeter using a stainless steel plate as a platform to support the test specimen. The back surface temperature and expansion height of the intumescent coating were measured as a function of time. Several factors such as heat flux, distance to cone heater and coating thickness were also investigated. The results showed that the normalized expansion height of intumescent coating was consistent at different heat flux levels. Hence the expansion of the coating can be considered to be dependent only on the mass loss rates and not the value of the external heat flux.Also, results from the cone tests, permit the formulation of an experimental protocol for evaluating of the thermal shielding efficiency of the intumescent coatings. The results showed that the data obtained using a cone calorimeter with 2.5 cm of distance cannot be compared with other distances, such as 4 or 6 cm. The present work also showed that the values of the relevant parameters did not differ significantly at distances to the cone heater above 4 cm.In a second evaluation, the new intumescent coating was applied to polyurethane and Gypsum boards, for study using cone calorimetry. The use of the coating led to a decrease in the peak of heat release rate for combustion of polyurethane. The application of a coating layer can be used to decrease the overall requirement of thickness of the Gypsum board without compromising its thermal insulation performance.     

Influences of Talc on Fire Performance of Low Density Polyethylene

In this paper the effects of talc on the ignition time, the burning rate and the downward flame spread rate of low density polyethylene were studied through the cone calorimeter test, the modified UL 94 vertical burning test and a designed downward flame spread experiment. Cone calorimeter tests show that the mass loss rate (MLR) and the heat release rate (HRR) decrease with increasing the talc content, which is ascribed to the residue formed by talc. When the loading of talc is low, talc powders aggregate to form separate talc tablets during burning, leading to the slight decrease of MLR and HRR. When the mass fraction of talc is higher than 20%, possibly the percolation threshold for barrier effect of talc, an integral crust covering the whole specimen surface is generated to act as a good heat and mass barrier, resulting in the significant drop of MLR and HRR. However, no evidence of char in the residue is found. The ignition time in both the cone calorimeter test and the modified UL 94 test initially decreases and then increases with increasing the talc content. It is supposed that the wick effect of talc aggregations reduces the ignition time while the dilution effect and the barrier effect delay the ignition time. The downward flame spread rate initially increases and then decreases with increasing the talc content, which is suspected to be related with the reduction of ignition time and melt flow rate during burning caused by talc.     

锥形量热计研究木材临界辐射能流和点燃温度

锥形量热计不但可以直接测量出材料的某些燃烧特性数据（如热释放速率、质量损失率、点燃时间等），而且可以根据所测得的数据间接得出材料的其它燃烧特性数据。笔者介绍了一种从锥形量热计测得的数据推导临界辐射能流和点燃温度的方法。     

Critical heat flux and mass loss rate for extinction of flaming combustion of timber

The critical mass loss rate and critical heat flux for self-extinction of flaming combustion during steady-state burning of timber was measured in this study for a range of timber species. A vertical mass loss calorimeter was used to provide the external heat flux and to measure the mass loss of the timber samples. The results showed that the critical mass loss rate was dependent upon the timber species but did not show a clear dependency with the timber density. Critical mass loss rates and heat fluxes for self-extinction exist for each of the timber species tested for both the solid timber and cross laminated timber (CLT). Debonding of both the char layer and the individual lamella of the CLT caused increased mass loss rates, re-ignition after self-extinction and increased flame lengths. Both char and ply fall-off were observed.     

设备尺度对可燃材料失重速率的影响

文章分别利用锥型量热计和火灾早期特性实验台对柞木的失重速度进行了实验测量。研究结果表明：尺度效应的作用非常明显。相同辐射能量条件下，相比于火灾早期特性试验台实验，锥型量热计实验中试样容易着火，而且过程中火焰稳定，火陷持续时间较长。     

辐射热作用下金属钠燃烧现象试验研究

在辐射热通量为25~60kW/m²条件下对利用锥形量热仪对金属钠的燃烧现象进行了研究,测量了燃烧尾气中的氧气含量与剩余物料的质量。结果表明:随着环境热通量增加,金属钠燃烧现象存在较大差异性,残留物数量逐渐减少至完全参与燃烧。当辐射热通量小于30kW/m²时,金属钠未出现明火燃烧;在外界辐射热通量为50~60kW/m²时,金属钠发生较不稳定、不充分的明火燃烧;当辐射热通量大于60kW/m²时,金属钠发生较为稳定且全面的明火燃烧。     

典型汽车内饰材料的燃烧特性研究

采用锥形量热仪实验对涤纶面料丙纶玻璃纤维板、涤纶面料丙纶麻纤维板和 PVC 革丙纶麻纤维板 3 种典型汽车内饰材料在 25、35、50 kW/m2 热辐射强度下的点燃时间、质量损失率、热释放速率等燃烧特性参数进行研究,并选取点燃预测模型计算材料的临界热辐射强度,使用轰燃倾向指数和热释放总量评价其潜在火灾危险性。结果表明,在实验热辐射强度下,涤纶面料丙纶麻纤维板质量损失百分率最大,结构完整性最差;涤纶面料丙纶玻璃纤维板平均点燃时间最短,临界热辐射强度最小,最容易被引燃;PVC 革丙纶麻纤维板热释放速率峰值最大,火灾性能指数最小,发生轰燃的可能性最大。     

历史文化街区、传统村落活化利用消防设计研究

摘 要：我国要求在城乡建设中系统保护、利用、传承好历史文化遗产,对于历史文化街区、传统村落的活化利用形成一批可复制可推广的经验。然而近年来相关火灾事故频发,火灾隐患整治和消防能力提升活动持续进行。归纳总结了国内外相关标准规范情况,针对历史文化街区、传统村落活化利用过程中消防设计难以遵照现行消防规范执行的现状,总结提炼出针对性消防设计的思路,从区域、建筑、监控管理三个层面提出消防设计策略。     

几种铺地材料燃烧性能的锥形量热计研究

利用锥形量热计对几种铺地材料的燃烧性能进行了研究。对几种各种铺地材料在不同热辐射条件下的点燃时间、热释放速率、质量损失速率、CO/CO2生成率等燃烧特性进行了定量研究,综合评价了材料的燃烧性能,初步探讨了机理。     

热塑性高分子材料强制点燃过程模拟与分析

采用锥形量热仪对典型热塑性高分子材料——聚甲基丙烯酸甲酯(PMMA)在不同外部入射热通量下进行了强制点燃的实验研究。在气相反应和固相反应动力学及传递过程分析的基础上，建立了热塑性高分子材料强制点燃过程的数学模型，通过数值分析的方法将点燃数据相关联，得到PMMA强制点燃的点燃时间与临界表面温度的表达式，并计算了PMMA不同外部入射热通量下强制点燃时间及点燃的临界表面温度。模拟计算结果与实验结果的比较表明，二者基本吻合。采用所得到的数据关联式对强制点燃过程的影响因素进行了定量分析。     

Large eddy simulation of compartment fire with solid combustibles

For properly describing practical building fire processes with solid combustibles, the pyrolysis kinetics model of solid combustibles and the large eddy simulation (LES) approach are applied to the simulation of the thermal decomposition of the polyurethane foam (PUF) slab and the space fire spread in a compartment. The instantaneous variations of the heat release rate of the PUF slab, the smoke temperature, and the smoke interface height with time are obtained under different ventilation conditions. They are in agreement with the measured data. The ventilation conditions have distinct effects on the interactions between the pyrolysis of the PUF slab and the space fire spread. Influenced by the space fire spread, the heat flux on the top plane of the PUF slab exhibits a non-uniform distribution. The PUF slab is consumed in an asymmetric manner.