New thermostable systems: 2. Structure/properties relationship of nadimide-terminated fluorinated polyimides

cited By 1International audienceThe thermomechanical properties of 12 nadimide endcapped oligomers synthesized by polycondensation of nadic anhydride (NA), hexafluoroisopropylidene-2,2′-diphthalic acid anhydride (HFDA) and phenylene diamines, meta (mPDA), para (pPDA) or 9,9-bis(4-aminophenyl)fluorene (cardo diamine) have been studied. The rheological curves obtained showed the presence of two relaxations: α, associated with the glass transition temperature, and β, due to local molecular movements with the glass transition. The temperature of the loss modulus G″ associated with these two relaxations varied in the domain of molecular weight M̄n according to a Fox-Flory relation. By studying the relationship between chemical structures and mechanical properties, the influence of endo/exo isomerization of the nadimide end groups on the glass transition temperature Tg has been demonstrated. For a given oligomer, the Tg value increases with increasing percentage of exo isomers. The thermo-oxidative stability of the HFDA, PDA and NA oligomers increases when the molecular weight increases

New thermostable systems: 1. Mechanism and kinetics of polycondensation and characterization of fluoro-nadimide end-capped oligomers

cited By 3International audienceThe reactivity of monomers in PMR (polymerization of monomeric reactants) mixtures has been investigated in methanol at room temperature. The monomers used were three aromatic diamines, meta-phenylene diamine (mPDA), para-phenylene diamine (pPDA), the 9,9-bis(4-amino phenyl) fluorene (Cardo diamine), hexafluoroisopropylidene-2,2 bis phthalic ether (HFDE) and nadic anhydride mono methyl ester (NE). Using titration, and 13C and 19F NMR, it was found that NE rapidly reacts with the three aromatic diamines to yield bisnadimides; the corresponding acid-amide intermediates were not detected. The diester HFDE, on the other hand, reacts only very slowly with the same diamines at room temperature in methanol. Telechelic polyimides with nadic terminations were prepared from these monomers and characterized with liquid phase 1H and 13C NMR and HPLC. This physico-chemical study showed that during synthesis, the endo (N) nadimides isomerize giving off a mixture of endo endo (NN), endo exo (NX) and exo exo (XX) end groups. In addition, a fine high-performance liquid chromatography analysis led to the separation of oligomers as a function of their polymerization degree, and for each molecular weight a mixture of isomeric chain end groups NN, NX, XX were separated

Municipal solid waste incineration bottom ash: Physicochemical characterization of organic matter

The aim of this work was to characterize the initial organic content of a selected municipal solid waste incineration (MSWI) bottom ash. This was realized by elemental carbon analysis using pyroanalysis of untreated samples. In addition, MSWI bottom ash extracts obtained by supercritical fluid extraction (SFE) or hot solvent extraction (Soxtec), were analyzed using gas chromatography (GC) coupled to either a mass spectrometry detector (MSD) or a microwave induced plasma atomic emission detector (MIP-AED). The results showed that the labile organic carbon fraction of the MSWI bottom ash is non-negligible (about 1400 $\mu$g/g) and that it includes mainly carboxylic acids, n-alkanes, steroids and phthalates. The latter two families, as well as polyaromatic hydrocarbons that were also determined, would appear to confer a toxic character on MSWI bottom ash. In light of the well-designing and operating of the incineration facility, the results seem to be representative of a widespread quality of bottom ash

Chemical characterization of municipal solid waste incineration residue: Dissolution of elements with a microwave-dilute acids digestion technique compared to conventional methods

The aim of this work was to evaluate the focused microwave technique in an open system for the rapid dissolution of elements in fly ash and filter cakes, in comparison to conventional wet and dry methods. The method involved 15 minutes of heating in microwave system in 2 N nitric or hydrochloric acid. It was tested on different types of samples and led to the dissolution of Ca, Na, K, Zn, Pb, As with 2 N HNO$_3$ or HCl and Cd, Hg with 2 N HNO$_3$ for subsequent determination by atomic emission or absorption spectrometry. Thereby this method represents a rapid sample preparation technique for chemical analyses

Thermal polymerization of arylacetylenes: 1. Study of a monofunctional model compound

International audienceThe thermal polymerization of arylacetylene compounds has been studied from a monofunctional model compound, 4-(hexyloxy)phenylacetylene I. I was synthesized and bulk polymerized under several experimental conditions. The reaction products were analysed by chromatography, spectroscopy and spectrometry techniques. The observed average polymerization degree is low. The lowest molecular weight compounds were isolated and identified: they are two naphthalenic dimers and three benzenic trimers. They represent 30 wt% of the whole polymerization product. We have shown also that the thermal polymerization of I is temperature and time dependent and that a depolymerization process takes place at high temperatur

Structure/properties relationship of nadimide-terminated fluorinated polyimides. Part II. New thermostable systems

cited By 5International audienceWe have established the chemical structure/mechanical properties relationships of new nadimide-terminated polyimides. Initially, the prepolymers were synthesized by polycondensation of nadic anhydride (NA), hexafluoroisopropylidene-2,2-bis(phthalic acid anhydride) (6HFDA) and two phenylene diamines, meta (mPDA) and para (pPDA) in N-methylpyrrolidone (NMP). After characterizing the microstructure and composition of these systems using Chromatographic (HPLC, SEC) and spectroscopic techniques (1H and 13C NMR), we determined their thermomechanical properties. The rheology curves obtained showed the presence of two transitions, α and β, associated with the glass transition and a second, sub-vitreous transition, because of local molecular movements. By studying the relationship between chemical structures and mechanical properties, we have shown the influence of endo/exo isomerization of nadimide extremities on the glass transition temperature Tg. In a given polymer, the value of Tg increases with increasing percentage of exo isomers

Etude des proprietes physico-chimiques et mecaniques d'un melange resine acetylenique - polyimide lineaire

Available from INIST (FR), Document Supply Service, under shelf-number : AR 15975 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEMinistere de l'Enseignement Superieur et de la Recherche, 75 - Paris (France)FRFranc

Bioaccumulation of chromium in aquatic macrophyte Borreria scabiosoides Cham. & Schltdl.

International audienceThe capacity of Borreria scabiosoides Cham. & Schltdl. growing in hydroponics solutions to remove Cr (III) from water was evaluated. This macrophytes efficiently removed Cr from water at concentrations of 25 and 50 mg/l Cr−1. High resolution imaging secondary ion mass-spectrometry (HRI-SIMS) measurements were performed using scanning ion microprobe at the University of Chicago (UC-SIM). The inductively coupled plasma sector type mass spectrometer (HR-ICP-MS) was used to analyse all samples. In general, plant roots exhibited higher metal concentrations than the aerial plants parts. Borreria shows promise for the removal and store Cr from contaminated wastewater. The ion images demonstrated that Cr is preferentially accumulated in cell walls and in some vacuoles of cortical roots cells. The number of Cr deposits are higher in cortical parenchyma, particularly in vacuoles and cell walls, compared to stellar tissue