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61.
62.
Ioannis Dosis Maria Athanasiadou Ioannis Athanassiadis Xanthippos Karamanlis 《International journal of environmental analytical chemistry》2013,93(12):1151-1165
Polybrominated diphenyl ether (PBDE) concentrations were determined in marine sediment samples collected from 7 different locations around Thermaikos Gulf in north Greece. PBDEs were detected in all sampling sites and their average total concentration (ΣPBDEs) ranged from 0.26 to 4.92?ng?g?1?d.w. Concentrations were an order of magnitude higher in locations outlining the inner part of the Gulf, which were also closer to industrial areas, sewage treatment plant discharges, the city's harbour and landfill area. These findings suggest pollution in the aquatic ecosystem from industrial and urban activities in the area. Congener profiles exhibit predominance of BDE-209, while concentrations of other PBDE congeners were usually lower, when compared to similar studies from other countries globally, indicating that Thermaikos Gulf is among the low-polluted areas. Statistical analysis showed significant differences among the higher polluted sampling stations. Statistically significant differences also existed between sampling stations with high and low PBDE concentrations. Correlations between congeners suggested local contamination sources; however, specific point sources of pollution were not established. 相似文献
63.
Sedigheh Basiri Soleyman Moinfar 《International journal of environmental analytical chemistry》2013,93(15):1453-1465
The method relies on selective complexation of As(III) with a suitable chelating agent followed by dispersive liquid–liquid microextraction (DLLME) method. Flame atomic absorption spectrometry (FAAS) equipped with microsample introduction system was utilised for determination of As(III). 1-Undecanol and acetone were used as extraction solvent and disperser solvent respectively. Some effective parameters on complex formation and extraction have been optimised. Under the optimum conditions, the enrichment factor of 108 for As(III) was obtained from 9.8?mL of water samples. The calibration graph was linear in the range of 2–15?µg?L?1 with detection limits of 0.60?µg?L?1 for As(III). The relative standard deviation (R.S.D.) for ten replicate measurements of 5.00?µ?gL?1 of As(III) was 6.2%. Operation simplicity and high enrichment factors are the main advantages of DLLME for the determination of As(III) without necessity for hydride generation in water samples. 相似文献
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65.
Three kinds of polyethylene glycol phosphates (PEGPs) toughening agents were synthesized by esterification of phosphorus pentoxide (P2O5) with polyethylene glycol and characterized by Fourier transform infrared spectra and 31P nuclear magnetic resonance. A series of lightweight phenolic foams toughened with different loadings of PEGPs were prepared. Optical microscopy results show that the addition of PEGPs with small molecular weight PEG improves the structural homogeneity of phenolic foams obviously. The flame retardancy of toughened phenolic foams was evaluated by using UL 94, limiting oxygen index, and cone calorimeter. The results indicate that the incorporation of PEGPs not only increases the toughness of phenolic foams but also improves their flame retardancy. Moreover, the thermal stability of PEGPs and the toughened foams was investigated by thermogravimetric analysis. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
66.
Poly(vinyl alcohol)/melamine phosphate composites (PVA/MP) as a novel halogen‐free, flame‐retardant foam matrix were prepared through thermal processing, and then their thermal stability and flame retardancy were investigated by thermo‐gravimetric analysis, micro‐scale combustion calorimeter, cone calorimeter, vertical burning test, and limiting oxygen index (LOI) test. It was found that the thermal stability and combustion properties of the PVA/MP composites could be influenced by the addition of MP. Compared with the control PVA sample (B‐PVA), in the PVA/MP (75/25) composites, the temperature at 5% mass loss (T5%) decreased about 10°C, the residual chars at 600°C increased by nearly 27%, the temperature at the maximum peak heat release rate (TP) shifted from 292°C to 452°C, and the total heat released and the heat release capacity (HRC) decreased by 28% and 14%, respectively. Moreover, the PVA/MP composites could reach LOI value up to 35% and UL94 classification V‐0, showing good flame retardancy. At the same time, both Fourier transform infrared and X‐ray photoelectron spectroscopy spectra of the residual chars from the PVA/MP composites demonstrated that the catalytic effect of MP on the dehydration and decarboxylation reactions of PVA, and the chemical reactivity of MP during the chars‐forming reactions could be used to account for the changed thermal stability and flame retardancy of the PVA/MP composites. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
67.
Novel oligomeric intumescent flame retardants, poly(amino phosphonate ester)s (PAPEs), containing both phosphorous and nitrogen, were synthesized by reacting diethyl phosphite with two different polyschiff bases obtained from the reaction of diamines with dialdehyde. The target PAPEs (designated as PAPE‐d and PAPE‐e, respectively) were characterized by 1H NMR, 31P NMR, Fourier Transform infrared spectroscopy, elemental analysis, gel permeation chromatography and thermogravimetric analysis (TGA) techniques. Thermal stability and flammability of ethylene‐vinyl acetate copolymer (EVA)/PAPE blends with various PAPE content were investigated by TGA, limited oxygen index (LOI), vertical burning test (UL‐94) and microscale combustion colorimeter (MCC). The results indicate that PAPEs effectively improve the flame retardancy of EVA. The EVA/30%PAPE‐e blend has a LOI value of 28, and its peak heat release rate (PHRR) value in MCC measurement is reduced by 36%. At the same time, the EVA/PAPE blends also have high yield of residual char, indicating that PAPEs are effective charring agents. Scanning electron microscopy observations of the residues of the EVA/PAPE blends show the existence of compact char layer on the surface of the residues, which is responsible for the improvement of the flame retardancy of EVA. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
68.
M. Thirumal Dipak Khastgir Nikhil K Singha B. S. Manjunath Y. P. Naik 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):704-712
Water blown rigid polyurethane foams (PUF) with organoclay/organically modified nanoclay (ONC) were prepared and their properties such as density, mechanical, morphological, insulation, thermal and flame retardant properties were studied. In this investigation, the ONC content was varied from 1 to 10 parts per hundred of polyol (php) by weight. It was observed that the compressive strength of ONC filled PUF increased up to 3 php of ONC loading and then it decreased. Wide angle X-ray diffraction and transmission electron microscopy studies indicated the exfoliated dispersion of ONC in PUF. The thermal conductivity of ONC filled PUF decreases up to 5 php and then increases. The glass transition temperature (Tg) of PUF decreases on loading of ONC. The TGA analysis shows that there is slight increase in degradation temperature with increase in ONC loading. The flame retardant properties (LOI and flame spread rate) are improved slightly on addition (3 php) of ONC filled PUF. 相似文献
69.
The flammability and the thermal oxidative degradation kinetics of expandable graphite (EG) with magnesium hydroxide (MH) in flame‐retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL‐94 test, and thermogravimetric analysis (TGA). The results show that EG is a good synergist for improving the flame retardancy of PP/MH composite and the effect is enhanced with decreasing EG particle size. The Kissinger method and Flynn‐Wall‐Ozawa method were used to determine the apparent activation energy (E) for degradation of PP and flame retarded PP composites. The data obtained from the TGA curve indicate that EG markedly increases the thermal degradation temperature of PP/MH composites and improves the thermal stability of the composites. The kinetic results show that the values of E for degradation of flame retarded PP composites is much higher than that of neat PP, especially PP/MH composites with suitable amount of EG, which indicates that the flame retardants used in this work have a great effect on the mechanisms of pyrolysis and combustion of PP. 相似文献
70.
Hossein Faghihian Alimohammad Hajishabani Shayesteh Dadfarnia Hassan Zamani 《International journal of environmental analytical chemistry》2013,93(4):223-231
A solid phase extraction system for separation and preconcentration of trace amounts of Pb(II), Ni(II), Cd(II) and Cu(II) is proposed. The procedure is based on the adsorption of Pb2+, Ni2+, Cd2+ and Cu2+ ions on a column of 1-(2-pyridylazo)-2-naphthol (PAN) immobilised on surfactant-coated clinoptilolite prior to their determinations by Flame Atomic Absorption Spectroscopy (FAAS). The effective parameters including pH, sample volume, sample flow rate and eluent flow rate were also studied. The analytes collected on the column were eluted with 5 mL of 1 mol L?1 nitric acid. A concentration factor of 180 can be achieved by passing 900 mL of sample through the column. The detection limits (3 s) for Cd, Cu, Pb and Ni were found to be 0.28, 0.12, 0.44 and 0.46 µg L?1, respectively. The relative SDs at 10 µg L?1 (n = 10) for analytes were in the range of 1.2–1.4%. The method was applied to the determination of Pb, Ni, Cd and Cu in water samples. 相似文献