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Retardants
Kinds of Retardants Terms modified by Retardants Selected AbstractsIn vivo and in vitro toxicity of decabromodiphenyl ethane, a flame retardantENVIRONMENTAL TOXICOLOGY, Issue 4 2010Tarja Nakari Abstract Toxicity of a relative new flame retardant, namely decabromodiphenyl ethane (DBDPE), marketed as an alternative to decabromodiphenyl ether (BDE-209) was assessed both in vivo and in vitro using the freshly separated fish hepatocyte assay and standardized water flea and zebrafish egg-larvae tests. The fish hepatocyte assay, based on the synthesis and secretion of vitellogenin from isolated male liver cells produced a clear dose-response curve in the presence of DBDPE. DBDPE induced the induction of hepatic ethoxyresorufin-O-deethylase (EROD) activity at low test concentrations, but started to inhibit the activity at higher concentrations. Also, the induction of the hepatocyte conjugation activity, uridinediphosphoglucuronosyltransferase (UDPGT), was induced with no signs of inhibition even at the highest test concentration. The reduced EROD activity resulted in a drop in the production of vitellogenin by the cells. In vivo tests showed that DBDPE was acutely toxic to water fleas, the 48 h EC-50 value being 19 ,g/L. Moreover, DBDPE reduced the hatching rates of exposed zebra-fish eggs and raised significantly the mortality of hatched larvae. Because there is hardly any information available on the effects of DBDPE on the aquatic environments, it is crucial to obtain more data on the effects and effective concentrations of DBDPE along with its occurrence in the environment. Such data would enable reliable assessments of the risks posed by this flame retardant. © 2009 Wiley Periodicals, Inc. Environ Toxicol 25: 333,338, 2010. [source] Fire hazard evaluation of thermoplastics based on analytic hierarchy process (AHP) methodFIRE AND MATERIALS, Issue 5 2010Baogang Yu Abstract Combustibility performance of 14 compositions including five main thermoplastics (polycarbonate (PC), polypropylene (PP), high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS) and poly (vinyl chloride) (PVC)) was tested by cone calorimeter. The fire growth index, total heat release amount index, total smoke release amount index and toxicity product index were calculated, based on which an index system for evaluating fire hazard was set up. All factors in this index system had been analyzed by the analytic hierarchy process, and the specific weight for each factor had been determined. Then fire hazard of thermoplastics was evaluated considering integrated fire hazard index. The results show that fire hazards of HIPS-phosphate fire retardant (PFR), PVC-non-flame retardant, ABS-brominated flame retardant (BFR) and PC/ABS-PFR are higher than PC-BFR and PP-non-halogenated flame retardant. Copyright © 2009 John Wiley & Sons, Ltd. [source] Graft copolymerization modification of silk fabric with an organophosphorus flame retardantFIRE AND MATERIALS, Issue 5 2010Guan Jinping Abstract This paper mainly deals with flame retardance of a silk fabric treated with a vinyl phosphate dimethyl 2-(methacryloyloxyethyl) phosphate (DMMEP) onto silk fabric by a graft copolymerization technique. This paper also explores the relationship between limiting oxygen index (LOI) and weight gain of DMMEP treated silk fabric. The paper also investigates the whiteness, handle, tensile strength and laundering durability of treated silk fabric. Microscale combustion calorimetry (MCC) is applied to test the heat release rate of silk fabric. Thermal gravimetric analysis (TG) and differential thermal analysis (DTA) are carried out to investigate the thermal decomposition behavior of DMMEP treated silk fabric. The kinetic parameters, activation energy and pre-exponential factor are determined using the Kissenger method. Copyright © 2009 John Wiley & Sons, Ltd. [source] Combustion properties of laminated veneer lumbers bonded with PVAc, PF adhesives and impregnated with some fire retardantsFIRE AND MATERIALS, Issue 3 2010eref Kurt Abstract In this study, the effects of impregnation materials di-ammonium phosphate, aluminium sulphate, potassium carbonate, calcium chloride, zinc chloride on combustion properties of 3 ply laminated veneer lumbers (LVL) produced from Walnut (Juglans regia L.) using phenol,formaldehyde (PF), poly (vinyl acetate) have been investigated. The pressure-vacuum method was used for impregnation process. Combustion test was performed according to the procedure of ASTM-E 69 standards. During the test, mass reduction, temperature and released gas (CO, NOX, SO2, O2) were determined every 30,s. As a result, zinc chloride was found to be the most successful fire-retardant chemical in LVL at PF adhesive. Since it diminishes combustion, the fire retardant of LVL produced from walnut using PF adhesive can be advised. Copyright © 2009 John Wiley & Sons, Ltd. [source] Zinc hydroxystannate-coated metal hydroxides as flame retardant and smoke suppression for flexible poly vinyl chlorideFIRE AND MATERIALS, Issue 4 2009Hongqiang Qu Abstract Zinc hydroxystannate (ZHS)-coated metal hydroxides were prepared. The effects of ZHS-coated metal hydroxides on flame retardancy and smoke suppression of flexible poly vinyl chloride were studied by means of the limiting oxygen index, smoke density rating and the char yield test. The mechanism was investigated by thermogravimerty (TG), differential thermal analysis, and differential TG analysis and scanning electron microscopy. The results showed that ZHS-coated metal hydroxides are more effective flame retardant and smoke suppressant than metal hydroxides, and it appears that tin compound may exert its action in both the condensed and vapor phases, but mainly in condensed phases as a Lewis acid. Copyright © 2009 John Wiley & Sons, Ltd. [source] The application of a novel flame retardant on viscose fiberFIRE AND MATERIALS, Issue 3 2009Jiang-tao Hu Abstract The paper is mainly about a novel organophosphorus flame-retardant N-1-chloroisopropyl alcohol-3-dimethylphosphonopropionamide. Dimethyl phosphate, acrylamide and epichlorohydrin were used as raw materials. The mechanisms of synthesis and molecule structure of the flame retardant were discussed. The fiber was treated using the pad-dry-cure-wash method. The limiting oxygen index value of the modified sample was 31%, higher than that of the sample treated with MDPA (Pyrovatex CP). After 50 laundry cycles, it still had some flame retardancy left. Thermogravimetry (TG) and Differentiate TG analyses confirmed that the flame retardant caused fiber to decompose below its ignition temperature and formed carbonaceous residue or char when exposed to fire. The treatment had an obvious effect on the denier of the fiber; the tensile strength of fiber slightly decreased, but that effect could be negligible. Copyright © 2008 John Wiley & Sons, Ltd. [source] Correlations between pyrolysis combustion flow calorimetry and conventional flammability tests with halogen-free flame retardant polyolefin compoundsFIRE AND MATERIALS, Issue 1 2009Jeffrey M. Cogen Abstract Seven halogen-free flame retardant (FR) compounds were evaluated using pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry. Performance of wires coated with the compounds was evaluated using industry standard flame tests. The results suggest that time to peak heat release rate (PHRR) and total heat released (THR) in cone calorimetry (and THR and temperature at PHRR in PCFC) be given more attention in FR compound evaluation. Results were analyzed using flame spread theory. As predicted, the lateral flame spread velocity was independent of PHRR and heat release capacity. However, no angular dependence of flame spread velocity was observed. Thus, the thermal theory of ignition and flame spread, which assumes that ignition at the flame front occurs at a particular flame and ignition temperature, provides little insight into the performance of the compounds. However, results are consistent with a heat release rate greater than about 66kW/m2 during flame propagation for sustained ignition of insulated wires containing mineral fillers, in agreement with a critical heat release rate criterion for burning. Mineral fillers can reduce heat release rate below the threshold value by lowering the flaming combustion efficiency and fuel content. A rapid screening procedure using PCFC is suggested by logistic regression of the binary (burn/no-burn) results. Copyright © 2008 John Wiley & Sons, Ltd. [source] Prediction of fire classification for wood based products.FIRE AND MATERIALS, Issue 3 2007A multivariate statistical approach based on the cone calorimeter Abstract Wood has long traditions as a building material, and is often used in construction elements, and as interior and exterior surfaces in the Nordic countries. In most applications, there are reaction to fire requirements to products used as surfaces, e.g. in escape routes and larger public spaces. Most wood products will therefore have to be treated with fire retardant (FR) agents to fulfil the strict requirements to properties connected to heat release and flame spread. Unfortunately, FR agents usually also increase the smoke production, as they cause a more incomplete combustion of the wood. The wood product manufacturers seek to find the optimal amount of FR additives where both heat release and smoke production in the classifying test are within the requirements given in the building regulations. This paper describes models for prediction of the European reaction to fire classes of wood products. The models are based on multivariate statistical analysis, and use test results from the cone calorimeter test as input. The presented models are, with very good precision, able to predict which Euroclass and additional smoke class a wood based product would obtain if it were to be tested in the single burning item test. Copyright © 2006 John Wiley & Sons, Ltd. [source] Flammability studies of sodium thiosulphate or metabisulphite impregnated wood using cone calorimeterFIRE AND MATERIALS, Issue 2 2007imkovic Abstract Spruce wood boards impregnated with Na2S2O3 or Na2S2O5 were studied with the cone calorimeter. The presence of Na2S2O3 lowered the average heat release rate in comparison to untreated material. The total amounts of CO and CO2 production were reduced by the treatment and also the specific extinction area and mass loss rate decreased. Washing of the salt from the material with water caused partial loss of the properties. Addition of the second impregnation step using acids (HCOOH, H3BO3 or H3PO4) resulted in the fixation of the sulphur in wood, but gave not the results of single-step modification for thiosulphate. With Na2S2O5 and without acid, the CO and time-to-ignition values were higher and average heat release rate smaller in comparison to unmodified material. Combined one step Na2S2O5/H3BO3 treatment lowered the CO, CO2 and specific extinction area values in comparison to the modification with Na2S2O5, similarly like it was observed for Na2S2O3/H3BO3 two-step-treatment. According to time-to-ignition values, Na2S2O5 alone at 5% addition is a better flame retardant than Na2S2O3 at 7%, but the effect is diminished at 10% amount or presence of acids. The total smoke release curves showed decrease due to modification in both phases of the process. Introduction of water washing as well as the acid treatment further lowered the values. The best results were achieved with 15% Na2S2O3,2% H3PO4,H2O system. According to the total smoke release curve the specimen produced more than five times smaller amount of smoke than untreated material in the first phase of the process. It seams that the concentration of Na2S2O5 is less affecting the properties than the synergistic effect of the Na2S2O3 or Na2S2O5/H3BO3 system. Although the level of smoke is low, the presence of elemental sulphur causes smaller times-to-ignition than on starting material. Copyright © 2006 John Wiley & Sons, Ltd. [source] Flame retardancy finish with an organophosphorus retardant on silk fabricsFIRE AND MATERIALS, Issue 6 2006Jin-Ping Guan Abstract The paper mainly deals with flame retardancy of silk fabrics treated with a commercial organophosphorus flame retardant [N-hydroxymethyl (3-dimethyl phosphono) propionamide (HDPP), also known as Pyrovatex CP], using the pad-dry-cure-wash method. The structures and properties of the treated and control sample are discussed. The Limiting Oxygen Index (LOI) value of the modified sample is above 30%. After 50 laundry cycles, it still has some flame retardancy left. HDPP and a cross-linking agent (HMM) were bound to silk fabrics which is confirmed by FT-IR spectra and amino analysis. The reaction degree of the flame retardant with silk is also high; almost all the tyrosine units have reacted, which can be confirmed by amino acid analysis. The reaction between flame retardant and silk only occurs in the amorphous region of silk fibre, which is confirmed by X-ray diffraction analysis and amino acid analysis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis show that the flame retardant causes silk fabrics to decompose below its ignition temperature (600°C) and formed carbonaceous residue or char when exposed to fire. The char behaves as a thermal barrier to fire, so silk fabrics show good flame retardancy. The treatment has a little effect on the whiteness of the silk fabrics and the tensile strength of treated silk fabrics slightly decreased; both effects are negligible. Copyright © 2006 John Wiley & Sons, Ltd. [source] Tetrakis(trimethysilyl)hypophosphate P2O2(OTMS)4: Synthesis, reactivity and application as flame retardantHETEROATOM CHEMISTRY, Issue 7 2007Catherine Ruflin The preparation of tetrakis(trimethy- silyl)hypophosphate, P2O2(OTMS)4 (TMS = SiMe3), which is easily obtained from cheap starting materials, is reported. Reaction with protic substrates (H2O, alcohols) proceeds under stepwise cleavage of silylethers, ROTMS, and formation of hypophosphoric acid, P2O2(OH)4. Amines in the presence of molecular sieves lead to desilylation and formation of ammonium salts of the [P2O2(OTMS)2(O,)2] dianion. On cotton fabrics, P2O2(OTMS)4 hydrolyzes to give P2O2(OH)4 within about 1 h when exposed to air, and this compound acts as an efficient flame retardant (limiting oxygen index >26%) even at low loadings (P content <3%). © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:721,731, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20373 [source] Preparation and flame retardancy of 2-EHA/n -BA acrylic PSA containing single and combined flame retardantsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Eun-Young Park Abstract UV curable acrylic PSAs (pressure-sensitive adhesives) were modified with organic and inorganic flame retardants to improve flame retardancy of PSAs minimize the sacrifice of adhesion properties. The flame retardancy (UL-94 test) of acrylic PSAs were enhanced by the addition of 5,30 wt % of an organic flame retardant such as TCEP (Tris(2-chloroethyl)phosphate), PBPE (pentabromophenyl ether), and TBBPA(3,3,5,5,-tetrabromobisphenol A). Especially, TBBPA is the best flame retardant for acrylic PSAs when it works alone. However, PSAs compounded with aluminum trihydroxide (Al(OH)3) showed a little reduction in burning time up to 30 wt %. An apparent synergic effect was observed only for an acrylic PSAs with a combination of TCEP and PBPE flame retardants. The addition of flame retardants brought a no significant effect on curing even in high amount. It was surmised that the miscibility between PSAs and flame retardant was closely related with flame retardancy and adhesion properties of acrylic PSAs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Lignin in jute fabric,polypropylene compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009B. A. Acha Abstract In this work, the feasibility of using lignin as a compatibilizer for composites made from jute fiber fabric and polypropylene (PP) was studied. Since lignin contains polar (hydroxyl) groups and nonpolar hydrocarbon, it was expected to be able to improve the compatibility between the two components of the composite. It was found that lignin acted as , nucleation, fire retardant, and toughening agent for PP matrix. Jute composites exhibit higher stiffness, tensile strength, and impact behavior in respect to those of neat PP. Although scanning electron micrographic observations indicate that PP-jute adhesion was slightly improved by lignin addition, additional benefits were only obtained from impact behavior. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Reactive extrusion to synthesize intumescent flame retardant with a solid acid as catalyst and the flame retardancy of the products in polypropyleneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Yuan Liu Abstract Reactive extrusion and solid acid catalysis technologies were adopted in the pentaerythritol,melamine phosphate (PER-MP) reaction to synthesize intumescent flame retardant, melamine salt of pentaerythritol phosphate (MPP), which was applied in flame retardant polypropylene (PP). This environment-friendly synthesis method provided a solution to the problems of conventional methods. On one hand, reactive extrusion in a twin screw extruder can effectively mix and transfer viscous materials that usually results in a tough stir in a conventional reactor, and achieve a continuous synthesis process. On the other hand, the solid acid, silicotungstic acid (STA) serving as a catalyst, can maintain a satisfactory conversion even with a low extrusion temperature and a short residence time, thus effectively suppressing foaming in the process of the reaction. Furthermore, without removal like other catalysts in general chemical reactions, STA was kept in produced MPP to constitute a synergism flame retardant system, therefore further improved the flame retardancy. LOI and UL94 test showed that the STA-catalyzed MPP (by reactive extrusion) possessed much better flame retardancy in PP when compared with the noncatalyzed MPP (by reactive extrusion), as well as present commercial MPP (by POCl3 method). In our investigation, the catalytic and synergistic effects of STA, as well as the related factors of the reactive extrusion affecting the conversion of the PER-MP reaction, flame retardancy and mechanical performance of the corresponding flame retardant PP, were systematically investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Immobilization of flame retardant onto silica nanoparticle surface and properties of epoxy resin filled with the flame retardant-immobilized silicaJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Takeshi Yamauchi Abstract To prepare silica nanoparticle having flame retardant activity, the immobilization of flame retardant onto hyperbranched poly(amidoamine) (PAMAM)-grafted silica was investigated. Grafting of PAMAM onto a silica surface was achieved in a solvent-free dry-system using PAMAM dendrimer synthesis methodology. The immobilization of bromine flame retardant, poly(2,2,,6,6,-tetrabromobisphenol-A) diglycidyl ether (PTBBA), was successfully achieved by the reaction of terminal amino groups of PAMAM-grafted silica (Silica-PAMAM) with epoxy groups of PTBBA. The immobilization of PTBBA was confirmed by FTIR and thermal decomposition GC-MS. The amount of PTBBA immobilized onto Silica-PAMAM was determined to be 60 wt %. PTBBA-immobilized Silica-PAMAM (Silica-PAMAM-PTBBA) was dispersed uniformly in a epoxy resin, and the epoxy resin was cured in the presence of hexamethylenediamine. Flame retardant activity of the epoxy resin filled with Silica-PAMAM-PTBBA was estimated by limiting oxygen index (LOI). The LOI of epoxy resin filled with Silica-PAMAM-PTBBA was higher than that filled with untreated silica and free PTBBA. It was confirmed that the flame retardant activity of epoxy resin was improved by the addition of the Silica-PAMAM-PTBBA. The elimination of PTBBA from the epoxy resin filled with Silica-PAMAM-PTBBA into boiling water was hardly observed by immobilization of PTBBA onto silica surface. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6145,6152, 2009 [source] Brominated flame retardants in US foodMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 2 2008Arnold Schecter Abstract We and others recently began studying brominated flame retardant levels in various matrices in the US including human milk and other food. This paper reviews the food studies. In our studies, ten to thirteen polybrominated diphenyl ether (PBDE) congeners were measured, usually including BDE 209. All US women's milk samples were contaminated with PBDEs from 6 to 419 ng/g, lipid, orders of magnitude higher than levels reported in European studies, and are the highest reported worldwide. We compared our market basket studies of meat, fish and dairy products with other US food studies of meat and fish. US studies showed somewhat higher levels of PBDEs than reported elsewhere. Fish were most highly contaminated (median 616 pg/g), then meat (median190 pg/g) and dairy products (median 32.2 pg/g). However, unlike some European countries where fish predominates, dietary intake of PBDEs in the US is mostly from meat, then fish and then dairy products. Broiling can decrease the amount of PBDEs per serving. We also measured levels of hexabromocyclododecane (HBCD), another brominated flame retardant, in human milk. The levels are lower than PBDEs, 0.16,1.2 ng/g, similar to European levels, unlike PBDEs where US levels are much higher than European levels. [source] Use of Turkish huntite/hydromagnesite mineral in plastic materials as a flame retardantPOLYMER COMPOSITES, Issue 10 2010Hüsnügül Y, lmaz Atay In this study, the flame retardancy properties of huntite/hydromagnesite mineral in plastic compounds were investigated for potential electrical applications. Before the production of composite materials, huntite/hydromagnesite minerals were ground to particle sizes of 10, 1, and 0.1 ,m. Phase and microstructural analysis of huntite/hydromagnesite mineral powders were undertaken using XRD and SEM-EDS preceding the fabrication of the composite materials. The ground minerals with different particle size and content levels were subsequently added to ethylene vinyl acetate copolymer to produce composite materials. After fabrication of huntite/hydromagnesite reinforced plastic composite samples, they were characterized using DTA-TG, FTIR, and SEM-EDS. Flame retardancy tests were undertaken as a main objective of this research. The size distribution and the mineral content effects are measured regarding the flame retardancy of the polymer composites It was concluded that the flame retardant properties of plastic composites were improved as the mineral content increased and the size was reduced. POLYM. COMPOS., 31:1692,1700, 2010. © 2010 Society of Plastics Engineers. [source] Flame resistance and foaming properties of NBR compounds with halogen-free flame retardantsPOLYMER COMPOSITES, Issue 12 2009SungCheal Moon Acrylonitrile butadiene rubber (NBR) foams compounded with various halogen-free flame retardants were prepared. The influence of nonhalogen flame retardants on the flame resistance and foaming properties of the NBR compounds were investigated. The foaming properties (expandability 980%,1050%, closed-cell structure) of NBR compounds with expandable graphite (EG) and ammonium polyphosphate (APP) flame retardants were similar to the NBR base compounds which contained primarily aluminum hydroxide (ATH). The heat release capacity (HRC) ranged from 10 to 74 J/g-K, the average heat release rate (A-HRR) ranged from 8 to 60 kW/m2, and the total heat release (THR) ranged from 2.6 to 7.3 MJ/m2 for the nonhalogenated NBR foams with closed-cell structure and were significantly decreased upon increasing the amounts of flame retardants. This reduction is attributed to the hard char formation and production of water from the interaction with ATH. The limiting oxygen index (LOI) and time to ignition (TTI) show opposite results. The smoke density (0.050,0.037) of the NBR foams with EG flame retardant was decreased when compared to the NBR foam (0.107). The EG flame retardant was more effective than the phosphorus/nitrogen flame retardants in reducing the HRR and smoke density. The use of both ATH and EG is very effective in improving flame resistance. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers [source] Effects of synthesis conditions on crystal morphological structures and thermal degradation behavior of hydrotalcites and flame retardant and mechanical properties of EVA/hydrotalcite blendsPOLYMER COMPOSITES, Issue 2 2007Longchao Du The effects of synthesis methods and reaction conditions on the crystal morphological structures and thermal degradation behavior of hydrotalcites have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size analysis (PSA), and differential thermal analysis (DTA). The flame retardant and mechanical properties of ethylene,vinyl acetate (EVA) blends with the corresponding hydrotalcites have been estimated by limiting oxygen index (LOI), UL-94, and mechanical measurements. The results from the XRD, TEM, and PSA demonstrate that the hydrotalcites synthesized by ultrasound method have larger crystal sizes and particle size distribution than those by mechanical stirring method. Higher reaction temperature, longer dripping time, and lower solution concentration can increase the crystal and particle sizes of ultrasound-synthesized hydrotalcites, whereas the longer ultrasound aging time can increase the crystal sizes and decrease the particle sizes of hydrotalcites because of the smashing conglomeration. The DTA data give a positive evidence that the hydrotalcite samples prepared by mechanical stirring method with longer alkaline dripping time have higher thermal degradation temperature than those by ultrasound method, since the ultrasound-synthesized hydrotalcites have more lattice defects than stirring-prepared hydrotalcites. The data from LOI, UL-94, and mechanical tests show that the ultrasonic-synthesized hydrotalcites have better flame retardant properties, whereas the stirring-synthesized hydrotalcites have better tensile strength in the EVA/hydrotalcite blends. POLYM. COMPOS., 28:131,138, 2007. © 2007 Society of Plastics Engineers [source] From carbon nanotube coatings to high-performance polymer nanocompositesPOLYMER INTERNATIONAL, Issue 4 2008Stéphane Bredeau Abstract Since their discovery at the beginning of the 1990s, carbon nanotubes (CNTs) have been the focus of considerable research by both academia and industry due to their remarkable and unique electronic and mechanical properties. Among numerous potential applications of CNTs, their use as reinforcing materials for polymers has recently received considerable attention since their exceptional mechanical properties, combined with their low density, offer tremendous opportunities for the development of fundamentally new material systems. However, the key challenge remains to reach a high level of nanoparticle dissociation (i.e. to break down the cohesion of aggregated CNTs) as well as a fine dispersion upon melt blending within the selected matrices. Therefore, this contribution aims at reviewing the exceptional efficiency of CNT coating by a thin layer of polymer as obtained by an in situ polymerization process catalysed directly from the nanofiller surface, known as the ,polymerization-filling technique'. This process allows for complete destructuring of the native filler aggregates. Interestingly enough, such surface-coated carbon nanotubes can be added as ,masterbatch' in commercial polymeric matrices leading to the production of polymer nanocomposites displaying much better thermomechanical, flame retardant and electrical conductive properties even at very low filler loading. Copyright © 2007 Society of Chemical Industry [source] Thermal behavior and flame retardancy of flexible poly(vinyl chloride) treated with Al(OH)3 and ZnOPOLYMER INTERNATIONAL, Issue 11 2005Hongqiang Qu Abstract Al(OH)3 as flame retardant and smoke suppressant for flexible poly(vinyl chloride) was evaluated alone and with ZnO, using thermal analytical techniques, limiting oxygen index and smoke density rating tests. The thermal behavior and flammability of the samples treated with Al(OH)3 and ZnO were studied by differential thermal analysis and thermogravimetric analysis. The activation energy was calculated by using the Vyazovkin model-free kinetic and Kissinger methods. The results showed that the flame-retardant and smoke-suppressant properties of the samples treated with Al(OH)3 and ZnO were related to the content of ZnO and the thermal effect during the process of thermal degradation of the samples. Copyright © 2005 Society of Chemical Industry [source] Preparation and characterization of microcapsulated red phosphorus and its flame-retardant mechanism in halogen-free flame retardant polyolefinsPOLYMER INTERNATIONAL, Issue 8 2003Qiang Wu Abstract Microcapsulated red phosphorus (MRP), with a melamine,formaldehyde resin coating layer, was prepared by two-step coating processes. The physical and chemical properties of MRP were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) and other measurements. The flame retardant action and mechanism of MRP in the halogen-free flame retardant (HFFR) polyolefins (PO) blends have been studied using cone calorimeter, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and dynamic FTIR spectroscopy. The results show that the MRP, which is coated with melamine,formaldehyde resin, has a higher ignition point, a considerably lower amount of phosphine evolution and of water absorption compared with red phosphorus (RP) itself. The data observed by cone calorimeter, LOI and TGA measurements from the PO/HFFR blends demonstrated that the MRP can decrease the heat release rate and effective heat of combustion, and increase the thermostability and LOI values of PO materials. The dynamic FTIR results revealed the flame-retardant mechanism that RP can promote the formation of charred layers with the P,O and P,C complexes in the condensed phase during burning of polymer materials. Copyright © 2003 Society of Chemical Industry [source] Flame retarded polymer layered silicate nanocomposites: a review of commercial and open literature systems,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2006Alexander B. Morgan Abstract This paper is a review of polymer nanocomposites used for flame retardancy applications, including commercial materials and open literature examples. Where possible, details on how the nanocomposite and flame retardant work together will be discussed. The key lesson from this review is that while the polymer nanocomposite can be considered to be flame retarded (or a flame retardant) by definition, these materials by themselves are unable to pass regulatory fire safety tests such as UL-94,V. Therefore, additional flame retardants are needed in combination with the polymer nanocomposite to pass these tests. In multiple examples, the nanocomposite works with other flame retardants in a synergistic or cooperative manner to lower the polymer flammability (heat release rate). Finally, a discussion on research needs and outlook for polymer nanocomposite flammability research is included. Copyright © 2006 John Wiley & Sons, Ltd. [source] Assessing the toxicity of TBBPA and HBCD by zebrafish embryo toxicity assay and biomarker analysisENVIRONMENTAL TOXICOLOGY, Issue 4 2009Jun Hu Abstract Tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) are two of the most widely used brominated flame retardants (BFRs). The biological toxicity effect of TBBPA and HBCD was studied by means of zebrafish embryo toxicity assays in combination with three biomarkers, including superoxide dismutase (SOD), lipid peroxidation, (LPO), and heat shock protein (Hsp70). The standard zebrafish embryo assay showed that high concentrations of TBBPA (,0.75 mg/L) can cause lethality or malformation. For HBCD within the concentration range (0.002,10 mg/L), no endpoint was observed. Furthermore, SOD activities of zebrafish embryos exposed to TBBPA were increased with the increasing concentrations. SOD activities in the group treated by HBCD showed an increase followed by a decline. Regardless of TBBPA or HBCD, LPO were increased along with the increase of the concentration. The change pattern of Hsp70 levels was the same with LPO. All these results showed that TBBPA and HBCD could cause oxidative stress and Hsp70 overexpression, inducing acute toxicity to zebrafish embryo in a short-term exposure. The study also indicates that the zebrafish embryo assay in combination with the biomarkers is effective in aquatic environmental toxicology and risk assessment. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009. [source] Accumulation and DNA damage in fathead minnows (Pimephales promelas) exposed to 2 brominated flame-retardant mixtures, Firemaster® 550 and Firemaster® BZ-54ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2010Jonathan S. Bearr Abstract Firemaster® 550 and Firemaster® BZ-54 are two brominated formulations that are in use as replacements for polybrominated diphenyl ether (PBDE) flame retardants. Two major components of these mixtures are 2,3,4,5-tetrabromo-ethylhexylbenzoate (TBB) and 2,3,4,5-tetrabromo-bis(2-ethylhexyl) phthalate (TBPH). Both have been measured in environmental matrices; however, scant toxicological information exists. The present study aimed to determine if these brominated flame-retardant formulations are bioavailable and adversely affect DNA integrity in fish. Fathead minnows (Pimephales promelas) were orally exposed to either FM 550, FM BZ54, or the nonbrominated form of TBPH, di-(2-ethylhexyl) phthalate (DEHP) for 56 d and depurated (e.g., fed clean food) for 22 d. At several time points, liver and blood cells were collected and assessed for DNA damage. Homogenized fish tissues were extracted and analyzed on day 0 and day 56 to determine the residue of TBB and TBPH and the appearance of any metabolites using gas chromatography-electron-capture negative ion mass spectrometry (GC/ECNI-MS). Significant increases (p,<,0.05) in DNA strand breaks from liver cells (but not blood cells) were observed during the exposure period compared with controls, although during depuration these levels returned to control. Both parent compounds, TBB and TBPH, were detected in tissues at approximately 1% of daily dosage along with brominated metabolites. The present study provides evidence for accumulation, metabolism, and genotoxicity of these new formulation flame retardants in fish and highlights the potential adverse effects of TBB- and TBPH-formulated fire retardants to aquatic species. Environ. Toxicol. Chem. 2010;29:722,729. © 2009 SETAC [source] Polybrominated diphenyl ethers, toxaphenes, and other halogenated organic pollutants in great blue heron eggsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2010Louise Champoux Abstract The great blue heron (Ardea herodias) has been used as a bioindicator of the state of the St. Lawrence River (Québec, Canada) since 1996. At 5-year intervals, selected breeding colonies along the River and its estuary are visited to estimate reproductive success and determine levels of contamination. Brominated flame retardants are found in many ecosystems and are increasing in concentration in the Great Lakes, which is the source of much of the water for the St. Lawrence River. In 2001 and 2002, in addition to polychlorinated biphenyls (PCBs) and chlorinated pesticides, the levels of polybrominated diphenyl ethers (PBDEs), polychlorinated bornanes (toxaphene) congeners and non- ortho -substituted PCBs were measured for the first time in pools of great blue heron eggs. The PBDE levels in great blue heron eggs (70,1,377,ng/g wet wt) were comparable to those measured in herring gull (Larus argentatus) eggs from the Great Lakes. Toxaphene was detected in great blue heron eggs at levels comparable to those of other major chlorinated pesticides. Major toxaphene congeners were octachlorobornane P44 and the nonachlorobornane P50. Environ. Toxicol. Chem. 2010;29:243,249. © 2009 SETAC [source] Polybrominated diphenyl ether flame retardants in Chesapeake Bay region, USA, peregrine falcon (Falco peregrinus) eggs: Urban/rural trends,,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2009Katherine E. Potter Abstract A total of 23 peregrine falcon (Falco peregrinus) eggs were obtained between 1993 and 2002 from 13 nests, encompassing 11 locations in the Chesapeake Bay region, USA. When multiple eggs were available from the same clutch, average clutch contaminant concentrations were calculated. An overall median total polybrominated diphenyl ether (PBDE) level of 201 ng/g wet weight was determined for the eggs/clutches examined. The maximum in an individual egg, from an urban highway bridge site, was 354 ng/g. This egg also exhibited the highest BDE 209 burden (48.2 ng/g). Compared to distributions reported in fish and piscivorous birds, falcon eggs were enriched in the more brominated congeners. The BDE congeners 153, 99, and 100 constituted 26.0, 24.8, and 13.1%, respectively, of total PBDEs. In most aquatic species, BDE 47 is the most abundant congener reported; however, it constituted only 4.4% of total PBDEs in the eggs of the present study. The median BDE 209 concentration was 6.3 ng/g. The sum of the octa- to nonabrominated congeners (BDEs 196, 197, 206, 207, and 208) contributed, on average, 14.0% of total PBDEs, exceeding the contribution of BDE 209 (5.9%). Concentrations of polychlorinated biphenyls (PCBs) and 1,1-dichloro-2,2-bis(p -chlorophenyl)ethylene (4,4,-DDE) also were determined in a subset of 16 eggs (collected in 2001,2002 from six nests) and were an order of magnitude greater than the corresponding PBDEs. Median BDE 209 concentrations were significantly correlated (p < 0.01, Spearman R = 0.690) with the human population density of the area surrounding the nest. Total PBDEs, total PCBs, and 4,4,-DDE levels were not correlated to human population density. [source] Reproductive health of bass in the Potomac, USA, drainage: Part 2.ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2009Seasonal occurrence of persistent, emerging organic contaminants Abstract The seasonal occurrence of organic contaminants, many of which are potential endocrine disruptors, entering the Potomac River, USA, watershed was investigated using a two-pronged approach during the fall of 2005 and spring of 2006. Passive samplers (semipermeable membrane device and polar organic chemical integrative sampler [POCIS]) were deployed in tandem at sites above and below wastewater treatment plant discharges within the watershed. Analysis of the samplers resulted in detection of 84 of 138 targeted chemicals. The agricultural pesticides atrazine and metolachlor had the greatest seasonal changes in water concentrations, with a 3.1- to 91-fold increase in the spring compared with the level in the previous fall. Coinciding with the elevated concentrations of atrazine in the spring were increasing concentrations of the atrazine degradation products desethylatrazine and desisopropylatrazine in the fall following spring and summer application of the parent compound. Other targeted chemicals (organochlorine pesticides, polycyclic aromatic hydrocarbons, and organic wastewater chemicals) did not indicate seasonal changes in occurrence or concentration; however, the overall concentrations and number of chemicals present were greater at the sites downstream of wastewater treatment plant discharges. Several fragrances and flame retardants were identified in these downstream sites, which are characteristic of wastewater effluent and human activities. The bioluminescent yeast estrogen screen in vitro assay of the POCIS extracts indicated the presence of chemicals that were capable of producing an estrogenic response at all sampling sites. [source] Emerging pollutants in the North Sea in comparison to Lake Ontario, Canada, dataENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2007Jens Arne Andresen Abstract In the present study, the concentrations and fate of contaminants such as organophosphate flame retardants and plasticizers, musk compounds such as galaxolide (HHCB), tonalide (AHTN), musk ketone and musk xylene, the bactericide triclosan, as well as the metabolites HHCB-lactone and triclosan-methyl were compared in the aqueous phase of the German Bight (North Sea). The concentrations of these compounds were around 1 to 10 ng/L in nearshore areas, and the concentrations were lower in the more pristine areas. The highest concentrations were determined for tris-(2-chloro- isopropyl) phosphate in the North Sea with concentration exceeding 10 ng/L even for the offshore samples. The samples contained 1 to 20 ng/L chlorinated organophosphates, approximately 1 ng/L nonchlorinated organophosphates, and 0.3 to 3 ng/L fragrance compounds. Some samples from Lake Ontario (Canada) were analyzed in comparison. Per capita emissions were calculated for both regions. These emissions were compared and turned out to be very similar for the Canadian and German locations. For the North Sea, some observations concerning stability, dilution, and degradation, as well as sources of the respective substances, were performed. These data indicate that the chlorinated organophosphates and some musk fragrances exhibit half lives exceeding the residence times and thus can be considered to be persistent in this ecosystem. In the German Bight, the river Elbe is the dominating source for the more hydrophilic compounds, such as chlorinated organophosphate flame retardants, which are diluted only into the North Sea. However, for the more lipophilic compounds such as the musk fragrances, different input patterns as well as distribution patterns are relevant, though the river Elbe is still a major source of pollution to the German Bight of the North Sea. The data seem to indicate either relevant inputs further west of the sampling area or mobilization from the sediments. [source] Effects of brominated flame retardants and brominated dioxins on steroidogenesis in H295R human adrenocortical carcinoma cell lineENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2007Ling Ding Abstract Brominated flame retardants (BFRs) and brominated dioxins are emerging persistent organic pollutants that are ubiquitous in the environment and can be accumulated by wildlife and humans. These chemicals can disturb endocrine function. Recent studies have demonstrated that one of the mechanisms of endocrine disruption by chemicals is modulation of steroidogenic gene expression or enzyme activities. In this study, an in vitro assay based on the H295R human adrenocortical carcinoma cell line, which possesses most key genes or enzymes involved in steroidogenesis, was used to examine the effects of five bromophenols, two polybrominated biphenyls (PBBs 77 and 169), 2,3,7,8-tetrabromodibenzo- p -dioxin, and 2,3,7,8-tetrabromodibenzofuran on the expression of 10 key steroidogenic genes. The H295R cells were exposed to various BFR concentrations for 48 h, and the expression of specific genes,cytochrome P450 (CYP11A, CYP11B2, CYP17, CYP19, and CYP21), 3,-hydroxysteroid dehydrogenase (3,HSD2), 17,-hydroxysteroid dehydrogenase (17,HSD1 and 17,HSD4), steroidogenic acute regulatory protein (StAR), and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR),was quantitatively measured using real-time polymerase chain reaction. Cell viability was not affected at the doses tested. Most of the genes were either up- or down-regulated, to some extent, by BFR exposure. Among the genes tested, 3,HSD2 was the most markedly up-regulated, with a range of magnitude from 1.6- to 20-fold. The results demonstrate that bromophenol, bromobiphenyls, and bromodibenzo- p -dioxin/furan are able to modulate steroidogenic gene expression, which may lead to endocrine disruption. [source] | ||||||||||||||||