Analysis of flammability and smoke emission of rigid polyurethane foams modified with nanoparticles and halogen-free fire retardants

Using one-step method, rigid polyurethane foams were made, modified with developed fire retardant systems containing halogen-free flame retardants and nanofillers in the form of multi-walled carbon nanotubes or nanoscale titanium dioxide. The materials were subjected to a test using a cone calorimeter and smoke-generating chamber, and selected samples were further analyzed via thermogravimetry and oxygen index. Moreover, the products of thermal degradation of selected samples were identified using gas chromatography with mass spectrometer. Conducted flammability tests confirmed the presence of a synergistic effect between the used nanofillers and halogen-free flame retardants. It has been observed that the carbonized layer, the formation of which favored the presence of nanoadditives, inhibits the combustion process. Furthermore, nanofillers influenced favorably reduction in the amount and the number of occurring products of thermal degradation.     

Fire retarded polyurethane foam composites based on steel slag/ammonium polyphosphate system: A novel strategy for utilization of metallurgical solid waste

A series of FR-RPUF composites were prepared by a one-step water foaming process with ammonium polyphosphate (APP) and steel slag (SS) as flame retardants. Thermogravimetric analysis (TG), limiting oxygen index (LOI), UL-94 vertical combustion test, microscale combustion calorimetry (MCC), TG-Fourier transform infrared spectrometry (TG-FTIR), scanning electron microscopy (SEM), Raman spectra and FTIR were used to investigate the thermal stability, flame retardancy, combustion performance, gas phase products, and char residue morphology of FR-RPUF composites. TG test results showed that the initial decomposition temperature (T_-5wt%) and char residue rate at 700°C of RPUF/APP/SS composites were significantly enhanced by the addition of APP and SS, and the thermal stability of the composites was improved. Flame retardant test results confirmed the significantly increased LOI values of RPUF/APP/SS composites with V-0 rating. TG-FTIR also confirmed the obviously decreased release of toxic gases and flammable gases in the combustion of RPUF/APP/SS composites. SEM and Raman spectra of char residues for the composites suggested that APP/SS system improved the compactness and graphitization degree of char layer for RPUF/APP/SS composite. The above researches provide a new strategy for the utilization of SS in fire safety engineering.     

Nanomorphology and fire behavior of polystyrene/organoclay nanocomposites containing brominated epoxy and antimony oxide

Organoclay nanocomposites were prepared by ultrasound‐assisted solution intercalation technique based on polystyrene containing brominated epoxy and a combination of brominated epoxy and antimony oxide. Aspects of nanomorphology and nanodispersion were investigated by X‐ray diffraction and transmission electron microscopy whereas flammability and reaction to fire were evaluated using limiting oxygen index, UL‐94, and mass loss calorimeter tests. Polystyrene/brominated‐epoxy‐blend‐based nanocomposites showed mixed intercalated–exfoliated nanomorphology where polymer‐intercalated crystallites predominantly exist in polystyrene matrix and exfoliated silicate layers reside on polystyrene/brominated epoxy phase boundaries and within brominated epoxy domains. Organoclay was found to impart a compatibilization effect on polystyrene and dispersed brominated epoxy, which facilitates uniform distribution of a fine flame‐retarding phase within the matrix. With the reduction of the rate at which decomposition products evolve into the gas phase, organoclay nanocomposites showed notable reductions in peak heat release rate and increases in limiting oxygen index. The gas‐phase hot radical entrapment by halogenated flame‐retardant system was coupled with the condensed‐phase physical action of nanodispersed organoclay, which increased the overall fire‐retardant effectiveness. Fire‐retardant mechanisms of nanocomposites based on polystyrene/brominated epoxy blends were attributed to nanoconfinement and tortuous pathway effects of organoclay rather than to carbonaceous char formation proposed earlier for polystyrene/organoclay systems without conventional flame retardants. Copyright © 2011 John Wiley & Sons, Ltd.     

Probing new approaches using atmospheric pressure photo ionization for the analysis of brominated flame retardants and their related degradation products by liquid chromatography-mass spectrometry

Atmospheric pressure photo ionisation has been evaluated for the analysis of brominated flame retardants and their related degradation products by LC-MS. Degradation mixtures obtained from the photochemical degradation of tetrabromobisphenol A and decabromodiphenylether were used as model systems for the assessment of the developed methodology. Negative ion mode gave best results for TBBPA and its degradation compounds. [M - H]- ions were formed without the need of using a doping agent. MS and MS/MS experiments allowed the structural identification of new TBBPA "polymeric" degradation compounds formed by attachment of TBBPA moieties and/or their respective cleavage products. In the case of polybromodiphenylethers, the positive mode provided M*+ ions and gave better results for congeners ranging from mono- to pentabromodiphenylethers whereas for higher bromination degrees, the negative ion mode (providing [M - Br + O]- ions) was best suited. Under both positive and negative ionisation modes, the use of toluene as doping agent gave better results. Liquid chromatography-mass spectrometry by means of atmospheric pressure photo-ionisation was applied to the analysis of aromatic brominated flame retardants and their degradation products. This methodology proved to be particularly useful, for the characterisation and structural identification of some compounds which are not amenable to GC-MS, especially in the case of apolar "polymeric" degradation products of tetrabromobisphenol A investigated in this work.     

The relationship between thermal degradation and flammability

The relationship between flammability and thermal degradation is the consequence of the burning cycle needed to sustain fire. Thermal degradation behaviour of polymers is discussed in relation to generation of fuel and other products, including flame quenchers, and the production of char. The thermal degradation behaviour of the main classes of fire retardant is considered and illustrated by examples of the ways in which specific fire retardants exert their effect on a particular polymer.     

Investigation of the flammability of different textile fabrics using micro-scale combustion calorimetry

Evaluating and analyzing the performance of flame retardant (FR) textiles are a critical part of research and development of new FR textiles products by the industry. The testing methods currently used in the industry have significant limitations. Most analytical and testing techniques are not able to measure heat release rate (HRR), the single most important parameter in evaluating the fire hazard of materials. It is difficult to measure HRR of textile fabrics using cone calorimetry because textile fabrics are dimensionally thin samples. The recently developed micro-scale combustion calorimetry (MCC) is able to measure the following flammability parameters for textile using milligram sample sizes: heat release capacity, HRR, temperature at peak heat release rate (PHRR), total heat release and char yield. In this research, we applied MCC to evaluate the flammability of different textile fabrics including cotton, rayon, cellulose acetate, silk, nylon, polyester, polypropylene, acrylic fibers, Nomex and Kevlar. We also studied the cotton fabrics treated with different flame retardants. We found that MCC is able to differentiate small differences in flammability of textile materials treated with flame retardants. We were also be able to calculate the limiting oxygen index (LOI) using the thermal combustion properties of various textile samples measured by the MCC. The calculated LOI data have yielded good agreement with experimental LOI results. Thus, we conclude that MCC is an effective new analytical technique for measuring textile flammability and has great potentials in the research and development of new flame retardants for textiles.     

Study on fire performance and pyrolysis of polyurethane foam material containing DMMP/TCPP

In this paper, an efficient flame retardant polyurethane foam (PUF) material consisting of phosphorus-halogen flame retardants has been prepared by adding dimethyl methylphosphonate (DMMP) and tris(1-chloro-2-propyl) phosphate (TCPP). The limiting oxygen index measurement and thermal analysis have been used for accessing the flame retardancy and thermal properties of the PUF sample. Thermal decomposition process of the sample and its evolved gaseous products at different temperatures during pyrolyzing have been investigated and identified via thermogravimetric analysis by coupling with Fourier transform infrared spectrometry. Influence of DMMP and TCPP on the evolved gaseous products during pyrolysis has been discussed here.     

Flame-retarding vinyl polymers using phosphorus-functionalized styrene monomers

Organohalogen compounds, principally brominated aromatics, continue to be the largest selling flame retardants worldwide. However, there is increasing concern about the bioaccumulation and potential toxicity of these compounds. Consequently, there is great interest in the development of effective alternatives to these materials. Organophosphorus compounds seem to offer the most promise as replacements for halogen-containing flame retardants. One approach to flame-retarding vinyl polymers is to develop reactive monomers containing high levels of phosphorus which may be incorporated directly into the polymer structure. Five phosphorus monomers for use in making fire-retardant copolymers with styrene have been synthesized. A comparative study of the thermal stability of the copolymers has been conducted. Preliminary potential fire behavior data have been obtained using pyrolysis combustion flow calorimetry.     

使用裂解气相色谱对几种阻燃聚丙烯材料热稳定性及阻燃机理的探讨

用裂解气相色谱（PyGC)考察了经三种类型阻燃剂（含磷、含溴、含溴和磷）改性的聚丙烯的热稳定性。利用PyGC-MS法分析不同样品的高温裂角产物,以此来推测阻燃材料受热分解时气相以及凝聚相所发生的反应,推断阻燃机理,分析影响阻燃效果的因素,为阻燃剂的开发提供有益参考。结果证实,它们都影响聚丙烯的热降解。溴系阻燃剂和磷系阻燃剂是分别从气相阻断、凝固相加速成炭实现阻止燃烧的,而磷-溴型阻燃剂同时具备单纯含磷或者含溴阻燃能力。     

Characterization of fire retardant polymer blends by temperature resolved in-source pyrolysis mass spectrometry

The characterization of fire retardant polymer blends by temperature resolved in-source pyrolysis mass spectrometry (PYMS) is demonstrated with a few examples. Electron impact (EI) and electron capture negative ionization (ECNI) were used to identify the thermal degradation products of polymer blends containing brominated fire retardants. PYMS (EI mode) offers an analytical instrument for a fast analysis of unknown mixtures of polymers and for the presence of fire retardant additives. Under electron impact conditions, in vacuo, low-molecular weight additives like fire retardants mainly evaporate from the polymer matrix. PYMS (EI mode) has been used for the characterization of addition polymers like polystyrene and acrylonitrile-butadiene-styrene copolymer, and for condensation polymers like the polyester poly(butylene terephthalate). Applying electron capture negative ionization, at low argon pressure in the ionization chamber, a more realistic pyrolysis situation is created because the premature loss of volatile additives is suppressed. The selectivity of ECNI for electron accepting groups like bromine makes it possible to study the influence of brominated compounds on the degradation processes in the melt. This is demonstrated by our studies on polystyrene and acrylonitrile-butadiene-styrene copolymer. High-molecular weight pyrolysis products in the m/z range of 1000 - 2000 are detected for p-bromopolystyrene and for a blend of high impact polystyrene with the fire retardant system decabromodiphenyl ether/antimony(III) oxide. In addition to the formation of antimony bromides shown in earlier studies, the emission of the synergist antimony(III) oxide as a dimeric cluster (Sb₄O₆) or as a reduced Sb₄ cluster is observed under PYMS conditions.     

Analysis of flame retardant additives in polymer fractions of waste of electric and electronic equipment (WEEE) by means of HPLC-UV/MS and GPC-HPLC-UV

An HPLC-UV/MS method has been developed to identify and quantify flame retardants in post-consumer plastics from waste of electric and electronic equipment (WEEE). Atmospheric pressure chemical ionisation spectra of 15 brominated and phosphate-based flame retardants were recorded and interpreted. The method was applied to detect flame retardant additives in polymer extracts obtained from pressurised liquid extraction of solid polymers. In addition, a screening method was developed for soluble styrene polymers to isolate a flame retardant fraction through the application of gel permeation chromatography (GPC). This fraction was transferred to an online-coupled HPLC column and detected by UV spectroscopy, which allowed a reliable qualitative and quantitative analysis of brominated flame retardants in the polymer solutions.     

Investigation of hexabromocyclododecane thermal degradation pathways by gas chromatography/mass spectrometry

The decomposition products of hexabromocyclododecane (HBCD), a widely used brominated flame retardant, were investigated by gas chromatography/mass spectrometry (GC/MS). HBCD thermal degradation was conducted under a moderate heating rate (10 degrees C/min) in a batch reactor using both inert and oxidizing atmospheres. GC/MS analysis allowed the identification of substances derived from the primary pyrolysis process at the moderate heating rates used. The presence of oxygen seems to have a negligible influence on the degradation products obtained in HBCD decomposition, at least at moderate heating rates. Based on the identified products, the main pathways of HBCD thermal degradation were assessed and a mechanism for HBCD decomposition was proposed. The results obtained indicate that hexa-, penta- and tetrabrominated polyaromatic structures seem not to be primary products of HBCD decomposition, and may only be obtained by secondary bromination reactions.     

苯基膦酸铈与十溴二苯醚在玻璃纤维增强聚对苯二甲酸乙二酯中的协同阻燃抑烟机理

采用熔融共混法制备了玻璃纤维增强聚对苯二甲酸乙二酯(PET-GF)/十溴二苯醚(DBDPO)/苯基膦酸铈(CeHPP)复合材料, 通过锥型量热仪(Cone)对复合材料的燃烧行为进行综合分析, 采用热失重-红外联用(TG-FTIR)分析了复合材料热降解过程中气体的释放量和主要成分, 并使用扫描电子显微镜(SEM)、 能量色散X射线光谱仪(EDX)和X射线光电子能谱(XPS)对复合材料燃烧后的残炭形貌、 残炭所含元素及含量等进行表征. 实验结果表明, 当CeHPP与DBDPO两者复配使用时, PET-GF/DBDPO/CeHPP复合材料的热解过程受到抑制, 凝聚相的燃烧减缓, 材料总的热分解量降低, 烟气释放量明显减小. 这主要是由于CeHPP在燃烧过程中形成了连续致密的残炭, 分布于基材和玻璃纤维表面, 将部分DBDPO及其分解产物滞留于凝聚相, 从而实现了气相-凝聚相双重阻燃作用, 有效阻隔了挥发性气体产物的释放.     

Thermal and spectroscopic studies of 2,3,5-trisubstituted and 1,2,3,5-tetrasubstituted indoles as non-competitive antagonists of GluK1/GluK2 receptors

This paper reports the thermal stability and thermal degradation of six derivatives of indole by means of TG-DSC (in air) and TG-FTIR (in nitrogen) techniques. The compounds were also characterized by infrared spectroscopy. In addition, IR spectra were calculated and compared with the experimental data. In particular, the potential energy distribution analysis was performed to assign IR signals. The studied compounds are characterized by good thermal stability in oxidizing and inert atmospheres which is important for potential medical application. Thermogravimetric measurements in air atmosphere showed that the decomposition of compounds proceeds in two or three main stages. The thermal degradation of compounds is preceded by the melting process. The pyrolysis of samples is a one-step process. Together with the analyses performed in nitrogen, the FTIR spectra of the evolved gas phase products were recorded. On the FTIR spectra of gaseous products, only the bands of water, carbon dioxide and carbon oxide molecules are present. In the case of indole derivatives containing the p-chlorobenzyl substituent in position 1, the bands of anisole, p-chlorotoluene and chlorobenzene also appear.     

Polypropylene fabrics padded with microencapsulated ammonium phosphate: Effect of the shell structure on the thermal stability and fire performance

Three types of microcapsules of di-ammonium hydrogen phosphate (DAHP) with different polymeric shells were evaluated as flame retardants in commercial polyurea padding for textiles. Encapsulated FR agent has the advantage of being compatible with the polymer matrix. The thermal degradation for the three types of DAHP microcapsules shows that our microcapsules act as intumescent fire retardants. The reaction to fire of polypropylene fabrics padded with FR polyurea loaded with neat DAHP or microencapsulated DAHP was studied with the cone calorimeter as a fire model.     

聚乙烯/石墨层间化合物热降解过程的TG-FTIR研究

将含磷化合物插层石墨层间化合物(GIC)用于聚乙烯(PE)的阻燃,采用氧指数(LOI)方法评价了PE/GIC的阻燃性能,并采用热分析-红外光谱联用技术(TG-FTIR)研究了PE/GIC的热降解过程,探讨了GIC的阻燃机理。研究表明,不同含磷化合物插层GIC阻燃聚乙烯的氧指数有显著差别,其中以多聚磷酸铵-GIC的阻燃效果较好,氧指数较高。TG-FTIR研究结果表明,GIC并未显著影响PE的热降解方式,但由于GIC体积膨胀所发生的氧化还原反应导致部分PE热降解提前并发生热氧化降解,促进了后期成炭的石墨化过程。     

The influence of an N-alkoxy HALS on the decomposition of a brominated fire retardant in polypropylene

This work studies the effect of an N-alkoxy HALS on the thermal decomposition of a brominated phosphate ester fire retardant. We have monitored the fate of the fire retardant in the presence of the N-alkoxy HALS during thermal decomposition using TGA, FTIR, TD-GC-MS, NMR and ESR methods. We have shown that the two additives interact in the condensed phase at temperatures below the onset of polymer decomposition to produce 1,3-dibromo-2,2-bis(bromomethyl)-propane as the main decomposition product. It is believed that this molecule is the key to the fire retardant action of the brominated phosphate ester because it readily decomposes to the effective gas phase flame inhibiting agent, HBr.     

The examination of bromine-containing fire retardants in unsaturated polyester resins by means of pyrolysis residue analysis

A method has been developed for following the bromine and weight losses of fire retarded UPE as a function of temperature. The results obtained by this method indicate that those bromine–containing fire retardants which exhibit a linear LOI–bromine concentration relation, the bromine concentration in the pyrolytically produced fuel remains more or less constant, while for those materials which deviate positively from the linear relation (that is they are more efficient), the bromine concentration in the fuel tends to peak at certain temperatures. When this effect is combined with variation in composition of the pyrolytic fuel, a situation can arise where a high bromine concentration coincides with a fuel particularly sensitive to flame quenching by bromine. Such a combined effect may be the reason why some brominated fire retardants are far more effective than others.     

Thermal degradation and intumescent flame retardation of cellulose whisker/epoxy resin composite

The morphology, thermal degradation, and flame retardancy of epoxy (EP) composites containing microcrystalline cellulose whisker (MCW) and microencapsulated ammonium polyphosphate (MFAPP) were investigated using optical microscopy, limiting oxygen index (LOI), UL-94, thermogravimetry (TG), microscale combustion calorimeter, and TG-FTIR. EP/MFAPP/MCW composites can pass V-0 in UL-94 test at 6 wt% loading, and its peak heat release rate decreases when compared with EP and EP/MFAPP. The reason is that the presence of MCW strengthens the charring capacity of EP composites in a fire. The results of TG and TG-FTIR show that at low temperature, MFAPP stimulates the dehydration of MCW and EP, and produces gas which is helpful for the formation of an intumescent char. Moreover, the residue at high temperature does not release any flammable gas and is a good insulation layer on the surface of the sample, which protects the underlying material in a fire.     

Kinetics of tetrabromobisphenol A pyrolysis. Comparison between correlation and mechanistic models

Brominated flame retardants are well recognized as being highly effective flame retardants. 4-4′-Isopropylidenebis(2,6-dibromophenol), commonly known as tetrabromobisphenol A, is the brominated flame retardant with the largest production volume and is used to improve fire safety, mainly of laminates in electrical and electronic equipment. A kinetic study of the pyrolysis of TBBA has been carried out to obtain decomposition parameters under different operating conditions and taking into account that TBBA is a compound with a high boiling point and that vaporization occurs simultaneously to decomposition. Dynamic runs and dynamic + isothermal run at different heating rates and using different masses of sample were correlated simultaneously. All TG runs were fitted with a unique set of kinetic parameters that is able to explain all the experiments. Moreover, a simplified detailed kinetic model has been developed and the kinetic parameters obtained satisfactorily reproduce the thermal decomposition of TBBA.