Simplified structure of the condensed phase of fire retarded PA6 nanocomposites in TGA as related flammability

This paper concerns with the analysis of the nature of the mass residue of PA6 and its nanocomposites in nitrogen. To assess the structure of the condensed phase during pyrolysis, this study presents thermal (by TGA in nitrogen) and condensed phase analysis of the residue (by FTIR-ATR) of PA6 nanocomposites consisting of phosphorous based flame retardants (FR) and/or nanoparticles (based on modified Montmorillonite clay). The thermal analysis reveals that the nanoparticles do not change the pyrolysis kinetics of PA6 whereas the FR does. The FR and NC used in the polymer nanocomposites (PNC) are capable of changing the structure of the char compared with pure PA6, where the char structure consists of polycyclic aromatic hydrocarbons (PAH) whereas the PA6 does not leave any considerable amount of mass residue. This residue analysis for decomposition samples in TGA in Nitrogen of the PA6/FR/NC composites complements previously published work for gas phase analysis ( FTIR-gas) as well as cone calorimeter characterization for their flammability. The overall aim, addressed here also, is to find out to what extent microscale measurements (e.g. TGA/FTIR/DSC/ATR) can be used a priori to delineate the flammability of polymer fire retarded composites. It is shown that FTIR-gas and FTIR (ATR) residue can be used to determine the fire retardant action (solid and/or gaseous) only qualitatively.     

Structure of the condensed phase and char of fire-retarded PBT nanocomposites by TGA/ATR in N2

Recently phosphorous-based fire retardants and nanoparticles are promoted as alternatives to halogenated fire retardants to reduce toxicological damage to the environment. To assess the condensed phase during pyrolysis, this study presents thermal (by TGA in nitrogen) and condensed phase analyses of the residue (by FTIR–ATR) of PBT modified by a phosphinate FR and/or nanoparticles (sepiolite). The thermal analysis shows that the nanoparticles do not change the pyrolysis kinetics of PBT whereas the phosphinate FR does. The condensed phase analysis shows that both the phosphinate FR and the nanoparticles change the structure of the char compared to the structure of the char from pure PBT. In contrast to the pure polymer, which leaves a char consisting of oligomeric components of PBT, the fire-retarded polymer (by phosphinate and /or nanoparticles) leaves a char consisting of polycyclic aromatic hydrocarbons (PAH). The PAH structure of the char is expected to make the char stronger and capable to withstand erosion in full-scale fire tests. This observation is verified from the strength analysis of the char residue in intermediate-scale flammability experiments, such as those in the cone calorimeter, where char is formed behind the flames in the absence of oxygen.     

利用CONE研究阻燃胶合板的动态燃烧行为

利用锥形量热仪CONE调查了磷氮硼系阻燃剂FRW处理胶合板在不同热辐射通量条件下的动态燃烧行为.结果显示:随热辐射通量提高,未阻燃胶合板的热释放速率峰值、烟气释放量和火势增长指数上升明显,火灾危险性高;阻燃胶合板的成炭率较高、热释放和烟释放较低;在燃烧过程中CO产率受热辐射通量增大的影响较小;FRW能显著抑制胶合板的可燃性,从而降低胶合板在使用过程中的火灾安全风险.     

Ignition of wood under time-varying radiant exposures

Many studies have utilized a small-scale experimental apparatus such as the cone calorimeter to investigate the piloted ignition of wood exposed to constant levels of incident heat flux; however, there is a deficiency of similar studies related to the non-piloted ignition of wood exposed to time-varying heat fluxes which might represent more realistic fire exposures. In this study, a method was established for producing well-controlled, time-varying exposures using the conical radiant heater of a cone calorimeter. Experiments were conducted in which the incident flux, time to non-piloted ignition, and back-surface temperature of spruce wood were measured. Measured data were used in combination with a numerical heat transfer model to compute the time-dependent temperature distribution through each specimen, and thereby deduce the surface temperature at ignition. From the 30 specimens tested, the average surface temperature for non-piloted ignition of wood was determined to be 521±10 °C. From this surface temperature range, the heat transfer model was used to predict the range of time over which non-piloted ignition was likely to occur for a given time-varying exposure. This procedure was found to produce excellent predictions of ignition time for the time-varying exposures considered in this study. In addition, several existing ignition models were considered, and their suitability for predicting the non-piloted ignition of wood was assessed.     

Fire behaviors of polymers under autoignition conditions in a cone calorimeter

Besides piloted ignition, autoignition is also an important aspect to real fire development as combustible materials may be ignited without independent flame. Fire behaviors of non-charring and charring polymers were then investigated in a cone calorimeter under autoignition conditions. Fire risk of non-charring polymers are higher than those of charring polymers because of high heat release, and the increase of heat release rate is much obvious with a higher heat flux or thickness. Charring polymers seem to have a higher CO yield, while non-charring polymers have a higher CO₂ yield. Ignition methods have influences to combustion efficiency of non-charring polymers as effective heat of combustion under autoignition are observed lower than those reference data under piloted ignition conditions. Its influences to charring polymers are not obvious. Both CO and CO₂ yields under flaming combustion are higher than those under non-flaming combustion, but mass percent of carbon seem to has limited effect. Experimental data in this study can provide a guidance to fire risk evaluation of non-charring and charring polymers.     

碳酸钾与硅溶胶复合对木材阻燃改性研究

为获得一种具有良好抑烟性能与抗流失性能的环保型木材阻燃剂,采用K2CO3与SiO2溶胶对杉木试件进行二次加压浸注处理,制得K2CO3/SiO2/木材无机质复合木材.采用锥形量热仪法(CONE)测试其阻燃性能,并测试了其抗流失性能.结果表明,杉木试件经K2CO3/SiO2复合处理后,点燃时间较未处理试件延长1倍左右,热释放速率及总量下降30％左右,抑烟性能非常显著；K2CO3/SiO2/木材的抗浸提值达到53％左右,具有较好的抗流失性能.     

Effects of nanoclay and fire retardants on fire retardancy of a polymer blend of EVA and LDPE

The effects of nanoclay (organoclay) and fire retardants (aluminium tri-hydroxide and magnesium hydroxide) on the fire retardancy of a polymer blend of ethylene-vinyl acetate (EVA) and low-density polyethylene (LDPE) were assessed using thermogravimetric analysis (TGA) and the cone calorimeter. TGA measurements were conducted in nitrogen and air atmospheres at different heating rates (1–20 °C/min), whilst in the cone calorimeter square samples were tested under various external heat fluxes (15–60 kW/m²). The TGA results indicate that the nanoclay (NC) alone has little effect on the degradation of the polymer blend, whereas aluminium tri-hydroxide (ATH) and magnesium hydroxide (MH), used as fire retardants (FRs), generally decrease the onset degradation temperature and also reduce the peak mass loss rate. However, it was found in the cone calorimeter that, though having negligible effect on ignition, the nanoclay reduces the heat release rate (HRR), and increases smoke and CO yields. In comparison, FRs (ATH or MH) were found to delay ignition owing to loss of water at lower temperatures, reduce the HRR, and have similar smoke and CO yields compared to the polymer blend. The reduced HRRs for both the nanoclay and FRs can be attributed to the formation of a surface layer (a nano layer for nanoclay and a ceramic-like layer of Al₂O₃/MgO for FRs), which acts as mass and heat barriers to the unpyrolysed material underneath. The global effect of the surface layer for the polymer blend nanocomposite was examined using a previously developed numerical model, and a methodology for predicting the mass loss rate was subsequently developed and validated.     

一种新型防火衬纸防火性能的研究

采用锥形量热仪对一种新研制的防火衬纸的防火隔热性能进行了比较全面的研究 ,研究结果表明 ,该防火衬纸具有较好的防火性能 ,具有实用价值     

热老化对阻燃PVC电缆燃烧性能的影响

采用锥形量热计对不同热老化程度的阻燃PVC电缆的引燃特性和热释放规律进行试验研究。结果表明,电缆试样的引燃时间随热老化程度的增加而延长,老化前期引燃时间增大较快,后期减缓;热释放速率的初始峰值随热老化程度的增加呈下降趋势;火灾性能指数随老化时间的延长总体呈下降的趋势。故与新投入使用的电缆相比,老化电缆的引燃危险和热危险相对减小。     

石墨烯微片对环氧树脂热性能的影响研究

研究石墨烯微片（GNS）对特种环氧树脂（AG-80/JD-919）的热稳定性和燃烧性能的影响。首先采用溶液共混法将GNS 添加到环氧树脂中,并利用热重分析仪（TGA）和锥形量热仪（CCT）分别对阻燃环氧树脂进行热稳定性和阻燃性能的测试分析。结果表明,GNS 添加量为6%时,环氧树脂的残炭量提高了4.6%,同时峰值热释放速率（pHRR）和总热释放量（THR）分别降低了40.63%和15.43%。因此,GNS 能够改善环氧树脂的热稳定性及其阻燃性能,这主要与GNS 在环氧树脂基体热分解过程能够起到物理阻隔作用有关。     

Pyrolysis and spontaneous ignition of wood under transient irradiation: Experiments and a-priori predictions

Wood is a material widely used in the built environment, but its flammability and response to fire are a disadvantage. Therefore, it is essential to have substantial knowledge of the behavior of wood undergoing external heating such as in a fire. The majority of studies in the literature use constant irradiation. Although this assumption simplifies both modelling and experimental endeavors, it is important to assess the behavior of materials under more comprehensive heating scenarios which might challenge the validity of solid-phase ignition criteria developed previously. These criteria are evaluated here for the spontaneous ignition under transient irradiation by combining experimental measurements and a-priori predictions from a model of heat transfer and pyrolysis. We have applied a two-step transient irradiation in the cone calorimeter in the form of a growth curve followed by constant irradiation. We use white spruce samples of size 100×100 mm and thickness of 38 mm . We measure the temperature at different depths and the mass loss. A one dimensional model written in the open source code Gpyro is used to predict the pyrolysis behavior. The model has a chemical scheme in which the components of wood (hemicellulose, cellulose, lignin) become active, then decompose in two competing reactions: one reaction to char and gas, and one reaction to tar. The kinetic parameters, as well as the thermal properties of the wood and char are taken from the literature, while ρ and moisture content are measured experimentally. A priori predictions of the temperature, made prior to the experiments, show excellent agreement with the measurements, being within the experimental uncertainty range. The mass loss rate (MLR) predictions are qualitatively similar to the measurements, but there is a large uncertainty in the measurements. For a-posteriori simulations, certain parameters are changed after having access to the measurements to improve the simulations. Also, we perform an evaluation of the solid phase ignition criteria used in the literature, and find that neither criteria is a consistent indicator of ignition. These results help understand the spontaneous ignition of wood subjected to transient irradiation and identify strengths and gaps in the topic.     

Preparation and properties of a single molecule intumescent flame retardant

Melamine salt of pentaerythriol phosphate (MPP), as a new single molecule intumescent flame-retardant, was prepared from pentaerythritol, phosphoric acid, and melamine, and then incorporated into polypropylene (PP) with organic montmorillonite (OMT) to obtain flame retardant PP/MPP/OMT composites. The flammability and combustion behavior of flame retardant PP composites were characterized by using LOI, UL-94 test, and cone calorimeter, respectively. The results showed that the flame retardant properties of the composite containing 29.0 wt% MPP and 1.0 wt% OMT are the best among all the composites. The digital photographs after cone calorimeter test demonstrated that moderate OMT could promote to form the homogenous and compact intumescent char layer.     

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。     

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。     

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。     

Evaluating the flammability of wood-based panels and gypsum particleboard using a cone calorimeter

This study examined the combustion characteristics of wood-based panels and gypsum particle board (GPB) made from wood particles using a cone calorimeter according to the ISO 5660-1 specifications. The combustion characteristics of the wood-based panels and GPB were measured in terms of the time to ignition (TTI), heat release rate (HRR), smoke production rate (SPR) and CO yield under a fire condition. The results demonstrated variations in the burning characteristics between the wood-based panels and a significant influence of the surface materials and construction elements on the HRR and SPR. The HRR, SPR and the CO yield of GPB were significantly lower than those of the wood-based panels.     

植酸三聚氰胺盐阻燃环氧树脂研究

利用生物基阻燃剂植酸三聚氰胺盐 (MPA) 阻燃改性环氧树脂并对其性能进行研究。通过红外光谱 (FTIR) 以及X射线光电子能谱 (XPS) 对MPA化学结构进行表征。利用热重分析仪 (TGA)、极限氧指数测试仪 (LOI)、垂直燃烧测试仪 (UL-94) 及锥形量热测试仪 (CC) 研究阻燃环氧树脂的热稳定性及阻燃性能。热重分析结果表明，MPA阻燃剂在800 ℃残炭达到25.6%，引入环氧树脂后可提升材料高温区热稳定性。垂直燃烧测试显示MPA在15%添加量下可赋予环氧树脂UL-94 V-0等级，表明MPA对环氧树脂有较好的阻燃效果。进一步锥形量热结果表明，MPA的加入显著降低了环氧树脂的热释放速率及总热释放，同时表现出优异的抑烟性能。     

低辐射强度下古建筑木构件材料的燃烧特性

为研究古建筑木构件材料在火灾下的燃烧特性,使用锥型量热仪对古木材试样的点燃时间、临界辐射强度、热释放速率、燃烧气体中CO2体积分数等燃烧特性进行试验研究。试验发现3种不同厚度试样的临界辐射强度分别为8.81,9.40,10.55 kW/m2。试样厚度增加会使古木材点燃时间延长,临界辐射强度增大,材料的热释放速率所形成的双峰值曲线的峰值降低。燃烧气体中CO2体积分数曲线与热释放速率所绘制出的曲线的形态一致,同一厚度的试样在不同辐射强度下其燃烧特性呈现出显著区别。与新木材相关燃烧特性参数对比,劣化后的古木材临界热辐射强度降低、点燃时间减小,5 min内平均热释放速率较高。研究表明,古建筑木构件材料燃烧特性有显著变化,可为古建筑火灾研究提供参考。     

Piloted ignition times,critical heat fluxes and mass loss rates at reduced oxygen atmospheres

Ignition, pyrolysis and burning of materials in reduced oxygen atmospheres occur when recirculating combustion gases are mixed with the air flowing into an enclosure. Still the incoming air can be sufficient for the complete combustion of the pyrolysis gases. Thus, for the prediction of fires in enclosures it is essential to understand the ignition and burning of materials in a reduced oxygen atmosphere even when plenty of oxidizer is available for complete combustion. Previous work employing gaseous fuels has shown that under these conditions, but before extinction, burning of gaseous fuels issuing from a nozzle is complete but radiation from the flames decreases owing to the reduction of their temperature. Complementary to that work, piloted ignition of solids is investigated here at reduced oxygen concentrations by measuring the ignition times and mass loss rates of the solid at ignition.These results were obtained in a cone calorimeter modified to supply air at reduced oxygen concentrations. Two types of plywood, normal and fire retardant 4 mm thick were examined at three imposed heat fluxes 25, 35 and 50 kW/m² and at oxygen concentrations of 21%, 18% and 15% by volume. Because heating at these heat fluxes and material thickness corresponds to intermediate thermal conditions (i.e. neither thin nor thick), novel analytical solutions are developed to analyze the data and extract the thermal and ignition properties of the material. The same novel solutions can be applied to modeling concurrent or countercurrent flame spread. Moreover, a theory for piloted ignition explains why the ignition times and mass pyrolysis rates are weakly dependent on reduced oxygen concentrations.     

Synergistic effects of hydroxy silicone oil on intumescent flame retardant polypropylene system

The effects of hydroxy silicone oil (HSO) as a synergistic agent on the flame retardancy of intumescent flame retardant polypropylene composites (IFR-PP) were studied, and the IFR system mainly consisted of the ammonium polyphosphate (APP) and pentaerythritol (PER). The UL-94 test, thermogravimetric analysis (TGA), cone calorimeter (CONE), digital photograph and X-ray photoelectron spectroscopy (XPS) were used to evaluate the synergistic effects of hydroxy silicone oil. It has been found that the Polypropylene (PP) composite containing only APP and PER does not show good flame retardancy at 30% additive level. The cone calorimeter results show that the heat release rate, mass, total heat release, carbon monoxide and carbon dioxide of PP/APP/PER/HSO composites decrease in comparison with the PP/APP/PER ternary composite. The digital photographs demonstrated that HSO could promote to form the homogenous and compact intumescent char layer. Thus, a suitable amount of HSO plays a synergistic effect in the flame retardancy.