Flammability and Thermal Oxidative Degradation Kinetics of Magnesium Hydroxide and Expandable Graphite Flame Retarded Polypropylene Composites

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.     

Use of clinoptilolite loaded with 1-(2-pyridylazo)-2-naphthol as a sorbent for preconcentration of Pb(II), Ni(II), Cd(II) and Cu(II) prior to their determination by flame atomic absorption spectroscopy

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.     

Method development for simultaneous analysis of HBCD,TBBPA, and dimethyl-TBBPA in marine biota from Greenland and the Faroe Islands

The brominated flame retardants hexabromocyclododecane (HBCD) and tetrabromobisphenol A (TBBPA) are high-production-volume chemicals. In recent years, their presence has been reported in sediment and biota from the marine environment. In this study, an analytical method was developed for the simultaneous determination of HBCD, TBBPA, and the possible metabolite dimethyl-TBBPA. The method was applied in a preliminary screening of egg, liver, and adipose tissue of marine biota from Greenland and the Faroe Islands. α-HBCD was detected in 35 of 36 analysed samples from the Arctic, indicating a ubiquitous presence of α-HBCD in the environment. β- and γ-HBCD were found in 10 and 14 samples, respectively. TBBPA and dimethyl-TBBPA were not detected in any of the samples indicating limited or no transport of these compounds to remote areas.     

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30?µg?L^?1 and 2.6?µg?L^?1, respectively. A precision expressed as relative standard deviation (RSD, n?=?10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.     

Cloud point extraction of aluminum (III) in water samples and determination by electrothermal atomic absorption spectrometry,flame atomic absorption spectrometry and UV-visible spectrophotometry

Cloud point extraction was applied as a preconcentration step for the determination of trace level of Al(III) in water samples with electrothermal atomic absorption spectrometry (ETAAS), flame atomic absorption spectrometry (FAAS) and UV-visible spectrophotometry. The aluminum was extracted as aluminum-Eriochrome Cyanine R (ECR) complex, at pH 6 by micelles of the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114). The investigations showed that the same CPE procedure can be used for different detection techniques. The results obtained from these techniques were evaluated. Under the optimal conditions, limit of detection obtained with ETAAS, FAAS and UV-visible spectrophotometry were 0.03 ng mL^?1, 0.06 µg mL^?1 and 0.01 µg mL^?1, respectively. The accuracy of the procedure was tested by analysing certified reference material. The method was successfully applied to determination of aluminum in water samples and dialysis fluid.     

Solid-phase extraction using multiwalled carbon nanotubes and quinalizarin for preconcentration and determination of trace amounts of some heavy metals in food,water and environmental samples

A solid phase extraction procedure has been developed using multiwalled carbon nanotubes (MWCNTs) as a solid sorbent and quinalizarin [1,2,5,8-tetrahydroxyanthracene-9,10-dione] as a chelating agent for separation and preconcentration of trace amounts of some heavy metal ions, Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II) before their determination by flame atomic absorption spectroscopy (FAAS). The influences of the analytical parameters, including pH, amounts of quinalizarin and adsorbent, sample volume, elution conditions such as volume and concentration of eluent, flow rates of solution and matrix ions, were investigated for the optimum recoveries of the analyte ions. No interference effects were observed from the foreign metal ions. The preconcentration factor was 100. The detection limit (LOD) for the investigated metals at the optimal conditions were observed in the range of 0.30–0.65 μg L^?1. The relative standard deviation (RSDs), and the recoveries of standard addition for this method were lower than 5.0% and 96–102%, respectively. The new procedure was successfully applied to the determination of analytes in food, water and environmental samples with satisfactory results.     

Flame Spray Pyrolysis for Finding Multicomponent Nanomaterials with Superior Electrochemical Properties in the CoOx‐FeOx System for Use in Lithium‐Ion Batteries

High‐temperature flame spray pyrolysis is employed for finding highly efficient nanomaterials for use in lithium‐ion batteries. CoO_x‐FeO_x nanopowders with various compositions are prepared by one‐pot high‐temperature flame spray pyrolysis. The Co and Fe components are uniformly distributed over the CoO_x‐FeO_x composite powders, irrespective of the Co/Fe mole ratio. The Co‐rich CoO_x‐FeO_x composite powders with Co/Fe mole ratios of 3:1 and 2:1 have mixed crystal structures with CoFe₂O₄ and Co₃O₄ phases. However, Co‐substituted magnetite composite powders prepared from spray solutions with Co and Fe components in mole ratios of 1:3, 1:2, and 1:1 have a single phase. Multicomponent CoO_x‐FeO_x powders with a Co/Fe mole ratio of 2:1 and a mixed crystal structure with Co₃O₄ and CoFe₂O₄ phases show high initial capacities and good cycling performance. The stable reversible discharge capacities of the composite powders with a Co/Fe mole ratio of 2:1 decrease from 1165 to 820 mA h g^?1 as the current density is increased from 500 to 5000 mA g^?1; however, the discharge capacity again increases to 1310 mA h g^?1 as the current density is restored to 500 mA g^?1.     

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.     

Synthesis and characterization of amino-terminated phosphorous polyborosiloxane and its effect on flame retardancy of polymethacrylimide

In this study, a novel flame retardant, that is, amino-terminated phosphorous polyborosiloxane (N-PBSi), was synthesized via a two-step polymerization reaction. The product's chemical structure was characterized firstly by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. It was proved that the prepared N-PBSi was indeed amino terminated and contained multiple flame-retardant elements including P, B, and Si. Besides, based on the variation of its FTIR spectra from room temperature to 700 °C and the subsequent thermogravimetric results, there also showed that the resultant N-PBSi had desirable thermal stability. This is a prerequisite for preparing flame-retardant polymethacrylimide (PMI) as PMI synthesis requires a high temperature treatment process up to 160 °C. On this basis, the condition for N-PBSi synthesis was then optimized to obtain flame retardants with better quality and higher yield. According to the experiments, the reactant ratio and reaction time were recommended to be 1:1.33:3 and 6 h, respectively. To evaluate the effectiveness of N-PBSi further, the flame retardancy of PMI with N-PBSi grafted was then investigated. The UL-94 rating and limiting oxygen index value of the PMI with 15 wt.% of N-PBSi incorporated were tested to be V-0 and 27%, respectively, indicative of greatly enhanced flame-retardant properties. In addition, the flame-retardant mechanism of N-PBSi on PMI was also discussed. Given all of these, the prepared N-PBSi as a reactive and effective flame retardant was promising for PMI.