Toughening of a High-performance Bis-nadimide Thermoset by Blending with High-Glass Transition Temperature Linear Polyimides

International audienceA nadimide end-capped thermosetting oligomer was modified by blending with three homologous soluble linear polyimides containing bulky lateral fluorene groups with the intention of improving its fracture toughness. These linear polyimides were prepared by polycondensation between 4,4′-(9H-fluoren-9-yliden)-bisphenylamine (cardo structure) and three different bis-phthalic anhydride derivatives, containing between the bis-phthalic moities a secondary alcohol function, a carbonyl function or a hexafluoropropylidene group respectively. The thermoset produced upon heating a thermostable polynadimide network having a glass transition temperature (Tg) close to 300° and a critical stress intensity factor equal to 0.9 MPa.m1/2. The Tgs of the studied linear polyimides were located above 340° in connection with the chain–chain molecular interactions. After dissolving, the precipitated blend powders with different compositions were thermally polymerized under pressure to give bulk specimens. The resulting morphologies were dependent on the chemical structure of the linear polyimide. As shown by the position of heat deflection temperatures, a well-defined two-phase blend was obtained by introducing the hexafluoropropylidene-containing polyimide, when a fully miscible system was formed with the secondary alcohol-containing polyimide. The parallel increase in fracture toughness seemed to be controlled by the degree of phase separation between the blend components. The greater improvement resulted from the partially fluorinated polyimide: the corresponding KIC reaching 1.23 MPa.m1/2 with 20 wt% of linear component. Finally, the toughening effect due to the latter polymer was examined in relation to its average molecular weight. Almost no change was observed if the corresponding inherent viscosity in N-methyl pyrrolidone solution was above 0.2 dl/g. In any case, owing to the high Tg of the linear component, the thermomechanical stability of the blend was maintained at the same level as that of the initial polynadimide networ

A simple LIBS method for fast quantitative analysis of fly ashes

International audienceAn evaluation of quantitative analysis of major elements (Ca, Al, Mg, Si and Fe) present in fly ashes was made using a simple and cost effective LIBS system. LIBS parameters were optimized to obtain best sensitivity and repeatability. In this purpose different binders were compared, leading to best sensitivity and mechanical stability when a binder containing silver and cellulose was employed in a 1:1 mass ratio.In order to be able to determine major elements in different fly ashes, a multi-matrix calibration was employed. Four reference materials were employed for calibration and five other fly ashes were selected as sample. Concentrations obtained by LIBS were compared to wet acid digestion and alkali fusion followed by ICP-OES analysis. Ca, Mg, Fe, Si and Al concentrations found using the LIBS method developed were in a good agreement with the values obtained by classical methods

Preparation of Thermostable Rigid Foams by Control of the Reverse Diels—Alder Reaction During the Cross-Linking of Bis-nadimide Oligomers

International audienceA new chemical approach using the polymerization of nadimide end-capped oligobenzhycholimide (BBN) was found to produce rigid thermostable foams. Two BBNs with a theoretical molecular weight of 1000 and 1500 D were prepared. Under thermal curing (up to 300 °C), cyclopentadiene evolution takes place through a reverse Diels-Alder reaction during the gelation of the systeme (cross over of storage and loss moduli). To obtain good mechanical properties, BBNs were blended with 3% of linear thermostable polymers. Foams with density ranging between 50 to 400 kg/m3 (3 to 25 lb/ft3) were prepared. These materials exhibit low moisture uptake (2.5%) and an onset of decomposition at about 350 °C. Other interesting features of these materials are their insulating properties, non flammable character and good compressive strength up to 300 °C

Fractionation of inherited and spiked antimony (Sb) in fluvial/estuarine bulk sediments: Unexpected anomalies in parallel selective extraction protocols

Selective extractions are widely used in sediment, soil and sludge samples to assess trace element carrier phases, mobility and potential bioaccessibility. Commonly used selective parallel extractions were applied to natural and isotopically-labelled bulk sediments from the Gironde fluvial-estuarine system and the Rhône River (France) to determine the solid phase fractionation of antimony (Sb), a priority contaminant in EU and US regulations and an important radionuclide in decay series occurring in the environment after nuclear power plant accidents. Antimony fractions obtained from several, parallel selective extraction solutions targeting Fe/Mn oxides (i.e., hydroxylamine-, oxalate- and ascorbate-based, herein assigned as fractions from “F2” solutions) and acid-soluble operationally defined phases (HCl- and HNO3-based, herein assigned as fractions from “F4” solutions) were compared (i) between each other's, and (ii) with those of other trace elements (Co, Cu, Ni, Pb, Zn, Th and U) in the same extractions. The solid fractionation of inherited Sb and spiked Sb was studied by applying a complete set of parallel selective extractions to isotopically-labelled sediments of the Gironde Estuary. Results suggest protocol-related and sediment-dependent anomalies in Sb selective extractions, compared to results expected from the operationally-defined extraction scheme and obtained for other trace elements. In fact, Sb fractions extracted with oxalate- and ascorbate-based solutions were greater than acid-soluble fractions (1M HCl and 1M HNO3) in the Garonne/Gironde fluvial estuarine sediments. A similar anomaly occurred for oxalate-based extractions of Sb in Rhône River sediments. These observations suggest that reducing conditions and the presence of strongly complexing organic ligands in the environment may mobilise respectively 2-fold and ~5-fold more Sb from natural bulk sediment and from sediments spiked with isotopically-labelled Sb than the acid-soluble fraction, usually used to assess the reactive, potentially bioaccessible fractions. The underestimation of the reactive, potentially bioaccessible fractions of Sb may bias the environmental interpretation of Sb solid fractionation and should be taken into account when assessing stable Sb cycles and Sb radionuclide dispersion scenarios in continent-ocean transition systems

Antimony in the Lot–Garonne river system: a 14-year record of solid–liquid partitioning and fluxes

Antimony is a trace element ubiquitously present in the environment, but data are lacking on its spatio-temporal distribution in aquatic environments. Long-term records serve as essential tools to decipher temporal patterns, historical sources and sinks and background concentrations in an area. We characterise the temporal concentrations, transport and behaviour of antimony in the Garonne River watershed, the main tributary to the Gironde Estuary, the largest estuary in south-west Europe. AbstractKnowledge of the environmental chemistry of antimony (Sb) in aquatic systems is limited, and a better understanding of its geochemical behaviour is needed. Based on a fourteen-year survey (2003–2016) with monthly measurements of dissolved and particulate Sb at five sites in the Lot–Garonne river system, combined with daily measurements of water discharge and suspended particulate matter, this work characterises Sb behaviour in the upstream major river watershed of the Gironde Estuary. The survey provides a first regional geochemical Sb background in the Garonne River watershed for dissolved (~0.2 µg L−1) and Th-normalised particulate Sb (Sbp/Thp ~0.25) concentrations. Observed decreasing temporal trends (<1 ng L−1 in dissolved and <0.02 mg kg−1 in particulate concentrations per month) at sites representing natural concentrations probably reflect global atmospheric Sb dynamics at the watershed scale. Regular seasonal cycles of solid/liquid partitioning, with higher solubility in summer (matching high dissolved and low particulate concentrations), reflect water-discharge and suspended particulate matter transport dynamics and possibly seasonal (bio)geochemical processes. Furthermore, this coefficient decreases from the river to the estuarine reaches (from average log10Kd 4.3 to minimum 3.7 L kg−1), suggesting an increased solubility of Sb in estuarine systems. Flux estimates indicate the relevance of the dissolved fraction in Sb transport (with negligible influence of the colloidal fraction) and a total flux (dissolved + particulate) entering the Gironde Estuary of 5.66 ± 2.96 t year−1 (~50 % particulate). These results highlight the importance of timescales and environmental parameters for understanding and prediction of future Sb biogeochemistry.AMORAD1Pour une gestion intégrée et durable des ressources en eau de bassins soumis à des pollutions industrielles et urbaines: étude comparative du Lot (France) et du Danshuei (Taiwan

Gas chromatographic–mass spectrometry and gas chromatographic–Fourier transform infrared spectroscopy assay for the simultaneous identification of fentanyl metabolites

Fentanyl, a synthetic opioid, undergoes important biotransformation to several metabolites. A gas chromatographic–mass spectrometric assay was applied for the simultaneous analysis of fentanyl and its major metabolites in biological samples. The identification of different metabolites was performed by gas chromatography–mass spectrometry (electronic impact and chemical ionisation modes) and gas chromatography–Fourier transform infrared spectroscopy. In the present study, rat and human microsomes incubation mixtures and human urines were analysed. In vitro formation of already known fentanyl metabolites was confirmed. The presence of metabolites not previously detected in human urine is described

Are Nano-colloids Controlling Rare Earth Elements Mobility or Is It the Opposite? Insight from A4F-UV-QQQ-ICP-MS

International audienceRare earth element (REE) mobility in the environment is expected to be controlled by colloids. Recent research has detailed the structure of iron-organic colloids (Fe-OM colloids), which include both large colloids and smaller nano-colloids. To assess how these nano-colloids affect REE mobility, their interactions with REE and calcium (Ca) were investigated at pH 4 and 6. Using Asymmetric Flow Field Flow Fractionation (A4F) combined with UV and Triple Quadrupole Inductively Coupled Plasma Mass Spectrometry (QQQ-ICP-MS), Fe-OM nano-colloids were separated from bulk Fe-OM colloids and their REE and Ca content were analyzed. Without REE and Ca, nano-colloids had an average diameter of approximately 25 nm. Their structure is pH-dependent, with aggregation increasing as pH decreases. At high REE loadings (REE/Fe ≥ 0.05), REE induced a size increase of nano-colloids, regardless of pH. Heavy REE (HREE), with their high affinity for organic matter, formed strong complexes with Fe-OM colloids, resulting in large aggregates. In contrast, light REE (LREE), which bind less strongly to organic molecules, were associated with the smallest nano-colloids. Low REE loading did not cause noticeable fractionation. Calcium further enhanced the aggregation process at both pH levels by neutralizing the charges on nano-colloids. These findings indicate that REE can act as aggregating agent controlling their own mobility, and regulating colloid transfer

Rare earth elements interaction with iron-organic matter colloids as a control of the REE environmental dissemination

International audienceRare earth elements (REE) are highly sought after for advanced technology, in response concerns about their environmental impact have arisen. The mobility and transport of REEs are influenced by their binding to solid surfaces, particularly colloids. With the widespread occurrence of REEs and their potential increase due to climate change, there is growing interest in understanding colloids composed of organic matter (OM) and iron (Fe). The reactivity of these colloids depends on their structural organization and the availability of Fe phase and OM binding sites. The effect of pH on the binding and mobility of REEs in these colloids in response to structural modification of Fe-OM colloids was investigated. REEs are primarily bind to the OM component of Fe-OM colloids, and their mobility is controlled by the response of OM colloids and molecules to pH conditions. At pH 6, the solubilization of small organic colloids (<3 kDa) control the REE pattern and subsequent speciation and mobility. In contrast, at pH 4, Fe-OM colloids bind less amount of REE but aggregate to form a large network. While most REEs remain soluble, those bound to Fe-OM colloids are expected to be immobilized through settlement or trapping in soil and sediment pores.This study supports the idea that colloids control the REE speciation and subsequent dissemination. The findings are particularly relevant for assessing the fate and ecotoxicology of REE in response to changing environmental conditions and increasing REE concentration in natural systems

Spatial variability of arsenic speciation in the Gironde Estuary: Emphasis on dynamic (potentially bioavailable) inorganic arsenite and arsenate fractions

Inorganic arsenic (As) speciation and behaviour were studied in the Gironde Estuary, a major European estuary in the south west of France. For the first time ever, the dynamic (potentially bioavailable) fraction of inorganic arsenite, As(III), and arsenate, As(V), were quantified in this estuary, using an antifouling gel-integrated gold microelectrode interrogated by square wave anodic stripping voltammetry (GIME-SWASV). The concentrations of dissolved As(III) and As(V) were determined by hydrid generation-flow injection-atomic absorption spectrometry (HG-FI-AAS) and inductively coupled plasma-mass spectrometry (ICP-MS) in collected samples following filtration through 0.2 μm, as well as 0.02 μm pore size filters. The concentrations of arsenite in the dynamic fraction, As(III)dyn, ranged from 1.3 to 3.3 nM, contributing almost completely to the dissolved arsenite, As(III)diss, which ranged between 0.9 and 3.1 nM in the 0.2 μm fraction, and between 1.2 and 3.7 nM in the 0.02 μm fraction. Concentrations of arsenate in the dynamic fraction, As(V)dyn, ranged from 0.9 to 22.9 nM, and contributed to the dissolved arsenate, As(V)diss, by 4–73% in the 0.2 μM fraction, and by 5–90% in the 0.02 μm fraction. The concentrations of As(V)diss in the 0.2 μm fraction were between 14.5 and 36.2 nM, and between 15.2 and 34.9 nM in the 0.02 μm fraction. The impact of this work is two-fold. Measurements of As species with different techniques allowed one to validate the on-board GIME voltammetric measurements. In addition, determination of As species in different fractions, as well as combining the obtained results with the conducted measurements of dissolved Mn and Fe, particulate suspended matters, and master physicochemical parameters (T, pH, O2, redox E), helped to broaden the understanding of biotic and abiotic processes governing the distribution of arsenic, especially its potentially bioavailable forms, in the Gironde Estuary