Application of an oxygen-shielded air-acetylene flame to atomic spectroscopy

A burner has been designed which provides an oxygen-shielded air-acetylene flame for atomic-absorption work. The chemical reducing properties of the oxygen-shielded flame operated under fuel-rich conditions are enhanced by the higher C: O ratio obtainable in the flame and by the higher flame temperature just above the reaction zone. The flame is inherently essentially free from the risk of flashback, and is offered as an alternative to the nitrous oxide-acetylene flame for use with certain types of equipment and for particular applications.     

Influence of oxidation state of phosphorus on the thermal and flammability of polyurea and epoxy resin

The focus of this study is an investigation of the effect of oxidation state of phosphorus in phosphorus-based flame retardants on the thermal and flame retardant properties of polyurea and epoxy resin. Three different oxidation states of phosphorus (phosphite, phosphate and phosphine oxide) additives, with different thermal stabilities at a constant phosphorus content (1.5 wt.%) have been utilized. Thermal and flame retardant properties were studied by TGA and cone calorimetry, respectively. The thermal stability of both polymers decreases upon the incorporation of phosphorus flame retardants irrespective of oxidation state and a greater amount of residue was observed in the case of phosphite. Phosphate was found to be better flame retardant in polyurea, whereas phosphite is suitable for epoxy resin. Phosphite will react with epoxy resin by trans-esterification, which is demonstrated by FTIR and ³¹P NMR. Further, TG–FTIR and XPS studies also provide information on flame retardancy of both polymers with phosphorus flame retardants.     

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。     

Study of quenching of S2 emission by addition of oxygen to a hydrogen flame in molecular emission cavity analysis

Interferences of oxygen on S₂ emission were measured for a hydrogen-oxgen flame in molecular emission cavity analysis and are discussed in terms of the emission intensities and temperatures in different regions of the flame. When a little oxygen is added to a hydrogen flame, S₂ emission is usually quenched. It also brings about a reduction in temperature in the lower region of the flame, where a cavity is introduced. However, in a “lower burnt hydrogen-oxygen flame”, in which hydrogen reacts instantly with added oxygen at the burner top, S₂ emission is not quenched by addition of oxygen, and the intensity and the flame temperature increase linearly with increasing oxygen flow-rate. Therefore, it is apparent that an increase in flame temperature is not responsible for the quenching. It is suggested that the existence of unburnt oxygen in the lower region of the flame can cause the quenching owing to the destruction of S₂ molecules to form sulphur-oxygen compounds.     

不同囊材聚磷酸铵微胶囊在环氧树脂中的阻燃研究

采用原位聚合法合成制备了以蜜胺树脂(MF)、环氧树脂(EP)以及EP和MF为囊材的微胶囊阻燃剂MFAPP、EPAPP、EMFAPP,用红外光谱(FT-IR)和扫描电镜(SEM)表征微胶囊阻燃剂的核壳结构。采用极限氧指数(LOI)和垂直燃烧等级测试(UL94)对MFAPP、EPAPP、EMFAPP在环氧树脂中的阻燃特性进行了研究。当添加量大于7%时,阻燃复合材料均能通过UL 94 V-0级测试,极限氧指数大于27.0%,表明MFAPP、EPAPP、EMFAPP均为EP的高效阻燃剂,这些阻燃剂在EP阻燃过程中均形成了膨胀炭层,属于膨胀阻燃机理。另外在耐水性实验中发现,添加EPAPP、EMFAPP的EP复合材料具有更好的耐水性,经75℃水浸泡6天后,阻燃性能得到了较好的保持。     

协效阻燃聚丙烯的阻燃性能

本文研究了以聚磷酸铵(APP)为主阻燃剂,次磷酸铝(AHP)和三聚氰胺氰尿酸盐(MCA)为辅阻燃剂的协效阻燃体系对聚丙烯(PP)阻燃性能的影响。 采用垂直燃烧测试、极限氧指数(LOI)测试、热重分析、锥形量热仪测试、扫描电子显微镜分析等技术手段对所制备的阻燃样品进行了阻燃性能分析。 结果表明:单独添加任一质量分数30%阻燃剂,均不能使PP获得良好的阻燃性能;当阻燃剂总质量分数保持在30%,m(APP)：m(AHP)：m(MCA)=4：1：1时获得理想阻燃效果,此时阻燃PP的LOI为33%,垂直燃烧测试达到V-0级,热释放速率峰值(PHRR)从765.7 kW/m²降为122.7 kW/m²。     

Control parameters of flame spreading in a fuel container

The processes involved in flame spreading over liquid fuels are subject of this work. A heat and momentum transfer analysis has been undertaken for fuel temperatures below the flash-point that confirms (within this range of temperatures studied in this work) that flame spreading is assisted by a convection pattern ahead of the flame. This assistance mechanism, which is not observed for solid fuels, is the origin (for lower temperatures) of a pulsating behaviour of the flame. A first experimental determination of the characteristic horizontal length of this assistance zone will be given. The analysis of our data lead us to conclude that flame spreading can be reduced by simultaneously preventing the formation of the convection zone and reducing the fuel surface temperature.     

聚对苯二甲酸丙二醇酯的无卤阻燃化改性

聚对苯二甲酸丙二醇酯作为新型聚酯材料,具有非常优良的性能,但其易燃性很大的限制了它的应用范围。为了提高对苯二甲酸乙二醇酯的阻燃性能,本文以无卤膨胀型EPFR-300A为阻燃改性剂,马来酸酐接枝聚烯烃(POE-g-MAH)弹性体为增韧剂,对聚对苯二甲酸丙二醇酯树脂(PTT)进行阻燃改性。通过热重分析仪(TGA)、示差扫描量热仪(DSC)、扫描电子显微镜(SEM)、力学性能等技术手段研究了阻燃剂和增韧剂对PTT树脂力学、热学和阻燃性能的影响。结果表明,增韧剂POE和POE-g-MAH的添加提高了PTT树脂的综合力学性能。当质量分数相同时,POE-g-MAH对PTT树脂的增韧效果要优于POE,且当POE-g-MAH质量分数为7%时,综合力学性能最佳。当添加相同质量分数增韧剂,EPFR-300A质量分数达到20%时,阻燃PTT材料阻燃性能最佳,极限氧指数(LOI)达到28.0%,垂直燃烧阻燃等级达到UL94 V-0级。EPFR-300A阻燃剂与PTT树脂间相容性良好,可以有效地促进PTT树脂成炭并提高材料的阻燃性能。     

The determination of magnesium in silicates by atomic absorption spectroscopy

The determination of magnesium in silicates by atomic absorption spectroscopy using a hot flame is discussed. Interference by aluminium observed, in the air-acetylene flame is overcome by using the hotter nitrous oxide-acetylene flame. There is some evidence to suggest that the alkali metals interfere in this determination but this is not confirmed in the results obtained on standard rock samples. Values for magnesium are given for some new rock standards recently distributed by the U.S. Geological Survey.     

Self-extinguishing polypropylene with a mass fraction of 9% intumescent additive II – Influence of highly oriented fibres

Recently, noticeably enhanced flame retardancy of multilayered self-reinforced composites, flame retarded with common ammonium polyphosphate based intumescent system, was described. In this paper the observed novel flame retardant synergism between intumescent additive system and highly oriented polymer fibres is further studied. The ignitability and combustion behaviour of flame retarded multilayer self-reinforced composites were compared to flame retardant compounds, prepared by simple melt compounding, of identical low additive contents, both when the heat was applied parallel (UL-94 tests) and perpendicular (cone calorimetric tests) with the direction of the embedded oriented tapes in self-reinforced composites. SEM and EDS analyses supported the different foaming process of the two types of samples to be understood, while the structure and character of the finally (after combustion) obtained charred layers were examined by compression tests. Considering the results of all the applied testing methods, the complex picture of the mechanism behind the enhanced flame retardant efficiency of flame retarded self-reinforced composites could be clarified.     

固定床天然气与煤共气化火焰区温度影响因素的研究

用实验室固定床反应器模拟合成气制备炉，考察了该工艺中不同因素对火焰区温度的影响。实验中首先确定了使火焰区温度最低时的甲烷和氧气相对入口位置，然后在此条件下分别考察了进料中H2O/O2和CH4/O2摩尔比变化对火焰区温度的影响。结果表明，甲烷和氧气相对入口位置平齐时火焰区温度最低，火焰区温度均随进料中CH4/O2和H2O/O2摩尔比的增大而降低。     

Comparison of atomic fluorescence power efficiencies for the helium-oxygen-acetylene and air-acetylene flames

Power efficiencies for five elements have been measured for the helium-oxygen-acetylene and air-acetylene flames. The increased power efficiencies found in this study for the helium-diluted flame, coupled with its enhanced atom-formation capabilities, suggest that lower atomic fluorescence detection limits should exist. However, in a comparison study with an air-acetylene flame using identical experimental conditions, a decreased atomic fluorescence signal-to-noise ratio was found for most elements in the helium-diluted flame. This decrease is ascribed to greater background emission noise in the hotter helium-diluted flame and decreased nebulization efficiency caused by the low density of the helium-containing nebulizer gas. A comparison of flame emission detection limits for the two flames confirms the increased sensitivity of the hotter helium-oxygen-acetylene flame, despite its lower nebulization efficiency.     

The chemistry of THPC–urea polymers and relationship to flame retardance on wool and wool–polyester blends. II. Relative flame-retardant efficiency on wool,polyester, and wool-polyester blends

Optimum flame retardance in THPC-urea-type formulations was achieved by approximately 1—0.9 THPC-urea mole ratio and slow urea addition. A phosphonium salt structure is more efficient in flame retarding 100% wool and wool-polyester blends than a phosphine oxide structure. Both structures are equivalent in flame retarding 100% polyester. It is considered probable that a vapor-phase mechanism is predominant in the phosphorus-based flame retardancy of wool, whereas a mixed solid-vapor phase mechanism operates for 100% polyester.     

Solubilities,thermostabilities and flame retardance behaviour of phosphorus-containing flame retardants and copolymers

Thirteen phosphorus-containing flame retardants were synthesized in this work. The solubilities of flame retardant [(6-oxide-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)-methyl]-butanedioic acid (DDP) in selected solvents are measured. TGA measurements of the 13 phosphorus-containing flame retardants were carried out and thermal stabilities of three flame-resistant PET (FRPET) resins were investigated. A FRPET incorporated by DDP with terephthalic acid and ethylene glycol reported in literature was also discussed and compared. The thermal stability of the FRPET is improved by the incorporation of phosphorus-containing flame retardants. The LOI values of all phosphorus-containing polyesters are higher than 27%. The improvement of the flame-resistant ability is due to the formation of the char that is not only caused by the existence of phosphorus elements in the resin but also by the relative large number of carbon atoms of the phenyl group in the flame retardants.     

Experimental determination of the flame expansion factor

The flame expansion factor (ratio of volumes of flame gases before and after burning) has been determined by mercury vapour introduction. The method is based on the determination of atomic concentration ratio in the flame and the flameless gas jet using the same sample introduction rate. A good agreement has been found between the expansion factors determined by the proposed method and those calculated by the gas law.     

Effect of ethyl‐bridged diphenylphosphine oxide on flame retardancy and thermal properties of epoxy resin

Three commercialized flame retardants, 1,2‐bis(diphenylphosphinoyl)ethane (EDPO), 6,6‐(1,2‐phenethyl)bis‐6H‐dibenz[c,e][1,2]oxaphosphorin‐6,6‐dioxide (HTP‐6123), and hexa‐phenoxy‐cyclotriphosphazene (HPCTP), were used to prepare the flame retardant diglycidyl ether of bisphenol A (DGEBA) epoxy resin (EP) under the same experimental conditions. The effects of T_g, thermal stability, and water absorption properties of EP caused by the three flame retardants were investigated and compared, together with their flame retardant efficiency. Results showed that the introduction of the three flame retardants improved the flame retardant performance of EP but led to decreases in T_g and decomposition temperature. EDPO showed higher flame retardant efficiency than the other two flame retardants. EP/EDPO showed higher thermal stability, better flame retardant performance, higher T_g value, and lower water absorption than EP/HTP‐6123 and EP/HPCTP. The study discovered that EDPO and HTP‐6123 primarily act through the gas phase flame retardant mechanism, while HPCTP is primarily driven by the condensed phase mechanism.     

A facile strategy to fabricate intumescent fire-retardant and smoke suppression protective coatings for natural rubber

As flammable natural rubber (NR) becomes more ubiquitous in industrial fields, there is a growing need for safe and effective flame retardant treatments through efficient techniques. Remarkably, our developed highly efficient natural tannic acid (TA)-based intumescent flame-retardant system (AGT) has the unique function in the rubber flame retardant aspect. Meanwhile, the developed coating method through polyurethane elastomer (PU) both as adhesive medium and a carbonforming agent can not only minimize the influence of flame retardant on the desirable intrinsic properties of base polymer and also maximize the efficiency of flame retardant. The flame-retardant coating (AGT/PU) exhibits highly efficient flame retardant performances reflected by a 31.9% reduction in peak heat release rate and a 27.3% reduction in total heat release and a 26.2% reduction in total smoke production with 50 wt% loading in 1 mm thick coating due to synergistic flame retardant effects. More importantly, the excellent flame retardancy performance are obtained by the PU@AGT10, as reflected in flame retardancy index (FRI) value of 11.88 makes it as excellent flame retardancy performance. While many physically mixed flame retardants are usually seriously detrimental to mechanical properties of NR, the influence of AGT/PU coating on mechanical properties of NR decreases obviously because fire retardant just directly impacts on PU adhesive layer rather than NR matrix, and the reinforcement function of graphene is also much significant. Moreover, the coating method requires just less flame retardant to achieve high flame retardant effect for NR. These findings suggest that significant opportunities for flame retardant polymer materials in industry.     

Experimental determination of the flame expansion factor

The flame expansion factor (ratio of volumes of flame gases before and after burning) has been determined by mercury vapour introduction. The method is based on the determination of atomic concentration ratio in the flame and the flameless gas jet using the same sample introduction rate. A good agreement has been found between the expansion factors determined by the proposed method and those calculated by the gas law.     

Effects of gas composition and flame sheathing on the spatial velocity profiles of laminar analytical acetylene flames

A recently developed technique has been employed to spatially map the rise velocity pronies (horizontal and vertical) of commonly used laminar analytical flames and to determine the influence on the profiles of fuel-to-oxidant ratio and the presence of a flame sheath. The rise velocities for fuel-rich, lean, and stoichiometric flames were found to differ substantially, the entire profile being greatest for the fuel-rich condition and lowest for the fuel-lean flame. In addition, the change in rise velocity with the addition of a solid (quartz tube) or gas (N₂) sheath was studied. The flowing sheath, at several different flow rates, affected each rise velocity profile principally by altering atmospheric entrainment and thereby changing secondary combustion in the flame. In contrast, a solid quartz tube used as a sheath produces an additional increase in the entire velocity profile of each flame, since it constrains gas expansion to the direction of flame propagation. The degree to which the velocity of each flame is affected by either a flowing N₂ and quartz sheath is strongly influenced by fuel-to-oxidant ratio.     

Characterisation of the dispersion in polymer flame retarded nanocomposites

Flame retardant nanocomposites have attracted many research efforts because they combine the advantages of a conventional flame retardant polymer with that of polymer nanocomposite. However the properties obtained depend on the dispersion of the nanoparticles. In this study, three types of polymer flame retarded nanocomposites based on different matrices (polypropylene (PP), polybutadiene terephtalate (PBT) and polyamide 6 (PA6)) have been prepared by extrusion. In order to investigate the dispersion of nanoparticles in the polymer containing flame retardant, conventional methods used to characterise the morphology of composites have been applied to FR composites containing nanoclays. XRD, TEM and melt rheology give useful information to describe the dispersion of the nanofiller in the flame retarded nanocomposite. In the PA6-OP1311 (phosphorus based flame retardant) materials, the clay is well dispersed unlike in PBT and PP materials where microcomposites are obtained with some intercalation. The poor dispersion is also highlighted by NMR measurements but the presence of flame retardant particles interferes in the quantitative evaluation of nanoclay dispersion and underestimations are made.