Influence of obstacle disturbance in a duct on explosion characteristics of coal gas

In combination with experimental research,numerical simulation is performed to investigate the influence law of the obstacles in a duct on the explosion flame of premixed coal gas and air. The numerical method uses upwind WENO scheme and two-step chemical reaction model. The interaction mechanism is addressed between the compression wave from reflection on the right end of the duct and flame propagation. The reflected wave is found to result in the decrease of flame velocity. On this basis,we analyze the me...     

Phosphorus‐containing renewable polyester‐polyols via ADMET polymerization: Synthesis,functionalization, and radical crosslinking

An α,ω‐diene containing hydroxyl groups was prepared from plant oil‐derived platform chemicals. The acyclic diene metathesis copolymerization (ADMET) of this monomer with a phosphorus‐containing α,ω‐diene (DOPO II), also plant oil derived, afforded a series of phosphorus containing linear polyesters, which have been fully characterized. The backbone hydroxyls of these polyesters have been acrylated and radically polymerized to produce crosslinked polymers. The thermomechanical and mechanical properties, the thermal stability, and the flame retardancy of these phosphorus‐based thermosets have been studied. Moreover, methyl 10‐undecenoate has been used as chain stopper in selected ADMET polymerizations to study the effect of the prepolymers' molecular weights on the different properties of the final materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1649–1660, 2010     

氢氧化镁-硼酸锌复合阻燃剂辅助制备产率高和电容性能优异的煤焦油沥青基多孔碳

以煤焦油沥青为前驱体，氢氧化镁-硼酸锌复合阻燃剂为助剂，直接在空气条件下高温碳化制备了煤沥青基多孔碳，并探究其电化学性能。得益于阻燃剂的阻燃作用协同其活化、掺杂功能化作用，得到了高产率(55.1%)、多原子(N、B、O)掺杂且具有分级多孔结构的多孔碳。将其作为超级电容器电极材料，在三电极体系中0.5 A·g^-1电流密度下比电容可达344 F·g^-1。此外，以制备的多孔碳和壳聚糖基氨基酸质子盐凝胶电解质组装的柔性对称电容器具有29.3 Wh·kg^-1的高能量密度，在50 000次循环后电容保持率为96.9%，且在-25~75℃温度区间内可正常工作，显示出宽的温度使用范围。     

Air-assisted liquid–liquid microextraction method as a novel microextraction technique; Application in extraction and preconcentration of phthalate esters in aqueous sample followed by gas chromatography–flame ionization detection

A novel microextraction technique, air-assisted liquid–liquid microextraction (AALLME), which is a new version of dispersive liquid–liquid microextraction (DLLME) method has been developed for extraction and preconcentration of phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP), di-n-butyl phthalate (DNBP), and di-2-ethylhexyl phthalate (DEHP), from aqueous samples prior to gas chromatography–flame ionization detection (GC–FID) analysis. In this method, much less volume of an organic solvent is used as extraction solvent in the absence of a disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GC–FID. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.12–1.15 and 0.85–4 ng mL⁻¹, respectively. Enrichment factors (EFs) and extraction recoveries (ERs) were in the ranges of 889–1022 and 89–102%, respectively. The relative standard deviations (RSDs) for the extraction of 100 ng mL⁻¹ and 500 ng mL⁻¹ of each phthalate ester were less than 4% for intra-day (n = 6) and inter-days (n = 4) precision. Finally some aqueous samples were successfully analyzed using the proposed method and three analytes, DIBP, DNBP and DEHP, were determined in them at ng mL⁻¹ level.     

Dispersive Liquid–Liquid Microextraction of Silver Prior to Determination by Microsample Introduction-Flame Atomic Absorption Spectrometry

Abstract

A new simple and sensitive method has been proposed for rapid determination of trace levels of silver in environmental water samples, using dispersive liquid–liquid microextraction (DLLME) prior to its microsample introduction-flame atomic absorption spectrometry. Under the optimum conditions, the linear range was 0.1–7 µg L^?1 and limit of detection was 0.018 µg L^?1. The relative standard deviation for 0.50 and 5.00 µg L^?1 of silver in water sample was 4.0 and 1.7%, respectively. The relative recoveries of silver from tap, well, river, and seawater samples at spiking levels of 1.00 and 5.00 µg L^?1 were in the range of 86.4–98.6%.     

Determination of Phosphorus in Detergents by Flame Emission Spectrometry

Abstract

Detergents are decomposed by heating and dissolved in water. Aliquots are ion-exchanged, and the solutions are aspirated into an air-hydrogen flame in contact with a cooled metal surface. The emission intensity of an HPO band at 526.2 mμ is measured. Results are given for four common detergents.     

HIPS/OMMT纳米复合材料的燃烧性能与其残余物炭层结构特征研究

采用SEM、XRD、TGA等分析方法对高抗冲聚苯乙烯/有机蒙脱土(HIPS/OMMT)纳米复合材料在燃烧过程中形成的炭渣残余物结构特征进行了研究,包括炭层断面形态,片层结构及炭渣热稳定性等.结果表明复合材料在热释放速率峰值之后,形成了具有阻燃作用的炭层结构,其特征是在炭层表面形成了一层比较薄但密实的皮层,皮层之下是较厚的一层蜂窝层,这种"皮-窝"结构赋予炭层良好的阻隔热的作用,减缓了热分解过程.XRD分析还表明原有插层结构经过燃烧已破坏,在皮-窝炭层中都已消失,结合SEM观察结果,蒙脱土片层多以剥离的单片层无规分布,皮层和窝层中聚合物已基本烧蚀,只剩下片状的蒙脱土聚集在一起形成了一种纳米尺寸的网状结构并包含了一定量的分解温度很高的碳质物质,不仅形成了稳定的保护层,而且碳质物质的生成也降低了材料分解挥发速率.窝层含有大量尺寸较大的空穴结构,隔气效果不如皮层,但显著地增大了炭层的体积,整体上能起到较大的隔热作用.二者共同构筑的皮-窝炭层结构在复合材料的燃烧过程中起到了阻燃的作用.     

The Effect of the Addition of Mg-Al LDH Intercalated with Dodecyl Sulfate on the Fire Retardancy Properties of Epoxy

Summary: Layered double hydroxides (LDH) are chemical compounds that can be added to polymeric resins to confer fire retardant characteristics. The focus of this work is to study the incorporation of LDH intercalated with dodecylsulfate anions into epoxy resins. The mechanical properties were investigated using tensile, flexural and impact mechanical tests. The flame-retardant properties were assessed using horizontal (UL 94 HB) and vertical burning (UL 94 V) tests. The highest tensile strength was obtained for the composite with 3 wt% of LDH, whereas the highest flexural strength was found by incorporating 1 wt% of LDH. All samples containing LDH showed self-extinguishing behavior in the vertical test and lower burning rate than pristine epoxy.     

Nanocarbon-Based Flame Retardant Polymer Nanocomposites

In recent years, nanocarbon materials have attracted the interest of researchers due to their excellent properties. Nanocarbon-based flame retardant polymer composites have enhanced thermal stability and mechanical properties compared with traditional flame retardant composites. In this article, the unique structural features of nanocarbon-based materials and their use in flame retardant polymeric materials are initially introduced. Afterwards, the flame retardant mechanism of nanocarbon materials is described. The main discussions include material components such as graphene, carbon nanotubes, fullerene (in preparing resins), elastomers, plastics, foams, fabrics, and film–matrix materials. Furthermore, the flame retardant properties of carbon nanomaterials and their modified products are summarized. Carbon nanomaterials not only play the role of a flame retardant in composites, but also play an important role in many aspects such as mechanical reinforcement. Finally, the opportunities and challenges for future development of carbon nanomaterials in flame-retardant polymeric materials are briefly discussed.     

Multi-residue analytical method for the determination of emerging pollutants in water by solid-phase extraction and liquid chromatography-tandem mass spectrometry

This paper describes the development and validation of a method for the simultaneous determination of 53 multi-class emerging organic pollutants in water samples using solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), using electrospray ionisation (ESI) in both positive and negative modes. Target compounds include acidic herbicides, UV filters, insect repellents, organophosphorous flame retardants, a bactericide, pharmaceuticals and metabolites. A single SPE consisting on the loading of 200-500 mL of sample adjusted to pH 7 on Oasis HLB 200mg cartridges and elution with methanol, permitted obtaining good recoveries: higher than 60% for tap, surface and wastewater in most cases. The 7 isotopically labelled internal standards effectively compensated losses during sample preparation and matrix effects at LC-MS/MS determination. The precision of the method, calculated as relative standard deviation (RSD) was below 15% for all compounds and all tested matrices. Detection limits (LODs) based on the confirmation, less intense, MRM (multiple reaction monitoring) transition and considering blanks varied between 0.3 and 30 ngL(-1). Finally, the developed method was applied to the determination of target analytes in various samples, including tap, surface and waste water. Among the tested emerging pollutants, 31 were found in wastewater in concentrations reaching up to 10 microgL(-1) in the case of ibuprofen. Also, 13 species were detected in tap water with concentrations up to 0.13 microgL(-1) for tri(chloropropyl) phosphate (TCPP).