Preparation of aqueous dispersion of thermoplastic sizing agent for carbon fiber by emulsion/solvent evaporation

In this work, different sizing agent aqueous dispersions based on polyetherimide (PEI) were elaborated in order to improve the interface between carbon fibers and a thermoplastic matrix (PEEK). The dispersions were obtained by the emulsion/solvent evaporation technique. To optimize the stability and the film formation on the fibers, two surfactants were tested at different concentrations, with different concentrations of PEI. The dispersions obtained were characterized by dynamic light scattering (DLS) and the stability evaluated by analytical centrifugation (LUMiFuge). The selected dispersions were tested for film formation ability by scanning electron microscopy (SEM), and the sizing performance was assessed by observation of the fiber/matrix interface by SEM. The results revealed that an aqueous dispersion of PEI,stabilized by sodium dodecyl sulfate as the surfactant, led to very stable sizing agent aqueous dispersion with ideal film formation and better interface adhesion

Caroline Galland, Pour la gloire de Dieu et du Roy. Les récollets en Nouvelle-France aux xviie et xviiie siècles, préface de Monique Cottret

Caroline Galland propose dans cet ouvrage issu de sa thèse de relever le défi d’écrire une histoire a priori impossible, celle des Récollets en Nouvelle-France, dont les archives brûlèrent en 1796. Elle procède donc au rassemblement d’une quantité de sources d’origines de valeurs hétérogènes, dont elle expose l’intérêt et la cohérence en une introduction richement charpentée de justifications méthodologiques, se prévalant de l’héritage d’Alain Corbin : « il s’agit de recomposer un puzzle à pa..

Evaluation of Organogel Nanoparticles as Drug Delivery System for Lipophilic Compounds

The purpose of the study was to evaluate organogel nanoparticles as a drug delivery system by investigating their stability, according to the formulation strategy, and their release profile. The gelled nanoparticles were prepared by hot emulsification (above the gelation temperature) of an organogel in water, and cooling at room temperature. In the first step, we used DLS and DSC to select the most suitable formulations by optimizing the proportion of ingredients (HSA, PVA, castor oil) to obtain particles of the smallest size and greatest stability. Then, two lipophilic drug models, indomethacin and ketoconazole were entrapped in the nanoparticles made of castor oil gelled by 12-hydroxystearic acid. Thermal studies (DSC) confirmed that there was no significant alteration of gelling due to the entrapped drugs, even at 3% w/w. Very stable dispersions were obtained (>3 months), with gelled oil nanoparticles presenting a mean diameter between 250 and 300 nm. High encapsulation efficiency (>98%) was measured for indomethacin and ketoconazole. The release profile determined by in vitro dialysis showed an immediate release of the drug from the organogel nanoparticles, due to rapid diffusion. The study demonstrates the interest of these gelled oil nanoparticles for the encapsulation and the delivery of lipophilic active compounds

Factors influencing the erosion rate and the drug release kinetics from organogels designed as matrices for oral controlled release of a hydrophobic drug

This article proposes solid-like systems from sunflower oil structured with a fibrillar network built by the assembly of 12-hydroxystearic acid (12-HSA), a gelator molecule for an oil phase. The resulting organogels were studied as oral controlled release formulations for a lipophilic drug, Efavirenz (EFV), dissolved in the oil. The effects of the gelator concentration on the thermal properties of the organogels were studied by Differential Scanning Calorimetry (DSC) and showed that drug incorporation did not change the sol–gel–sol transitions. The erosion and drug release kinetics from organogels under conventional (filling gelatin capsules) or multiparticulate (beads obtained by prilling) dosage forms were measured in simulated gastric and intestinal fluids. EFV release profiles were analyzed using model-dependent (curve-fitting) and independent approaches (Dissolution Efficiency DE). Korsmeyer–Peppas was the best fitting release kinetic model based on the goodness of fit, revealing a release mechanism from organogels loaded with EFV different from the simple drug diffusion release mechanism obtained from oily formulations. From organogels, EFV probably diffuses through an outer gel layer that erodes releasing oil droplets containing dissolved EFV into the aqueous medium

Original Preparation of PEKK Dispersion for Coating by Transfer from a Chloroform Stable Dispersion to an Aqueous Stable Dispersion, by Emulsion/Solvent Evaporation

In this work, aqueous dispersions of PolyEtherKetoneKetone (PEKK) oligomers were obtained by an emulsion/dispersion solvent evaporation technique. The PEKK oligomers were synthesized by a Friedel–Crafts acylation with a number average degree of polymerization of 4. The synthesized PEKK oligomers had very good thermal stability and spontaneously formed a stable dispersion of swollen micrometric fibers in chloroform. After sonication of the chloroform dispersion in water in the presence of sodium dodecyl sulfate (SDS) and evaporation, we obtained aggregated particles with a mean diameter between 120 and 160 nm, decreasing linearly with the PEKK concentration. The most stable dispersions were obtained with 0.5% wt of surfactant and, at a fixed concentration of SDS, the stability decreased when the PEKK concentration was increased. The different dispersions of PEKK in water were very stable and, after water evaporation, formed homogeneous films for high-performance coating

Trace-element imaging at macroscopic scale in a Belgian sphalerite-galena ore using Laser-Induced Breakdown Spectroscopy (LIBS)

Laser-Induced Breakdown Spectroscopy (LIBS) is a fast in-situ analytical technique based on spectroscopic analysis of atomic emission in laser-induced plasmas. Geochemical mapping at macroscopic scale using LIBS was applied to a decimetric Zn-Pb ore sample from east Belgium, which consists of alternating sphalerite and galena bands. A range of elements was detected with no or minimal spectral correction, including elements of interest for beneficiation such as Ge, Ag and Ga (although the detection of gallium could not be confirmed), and remediation, especially As and Tl. The comparison between LIBS and Energy Dispersive Spectroscopy (EDS) analyses showed that LIBS intensities reliably relate to elemental concentration although differences in spot size and detection limits exist between both techniques. The elemental images of minor and trace elements (Fe, Cu, Ag, Cd, Sb, As, Tl, Ge, Ni and Ba) obtained with LIBS revealed with great detail the compositional heterogeneity of the ore, including growth zones that were not visible on the specimen. In addition, each mineral generation has a distinct trace-element composition, reflecting a geochemical sequence whose potential metallogenic significance at the district scale should be addressed in further work. Although qualitative and preliminary, the obtained LIBS dataset already produced a wealth of information that allowed to initiate discussion on some genetical and crystallochemical aspects. Above all, LIBS appears as a powerful tool for screening geochemically large samples for the selection of zones of particular interest for further analysis.LIBS Scree

Effect of PEKK oligomers sizing on the dynamic mechanical behavior of poly(ether ketone ketone)/carbon fiber composites

Poly(ether ketone ketone) (PEKK)/unidirectional carbon fiber (CF) composites have a poor interface. Accordingly, PEKK oligomer (PEKKo) sizing with a chemical compatibility with PEKK is proposed for promoting interfacial interactions in order to enhance mechanical performances. The thermal stability until 500 °C has been shown by thermogravimetric analysis (TGA). In order to compare static and dynamic sizing methods, “lab sizing” and “pilot sizing” were carried out. Scanning electron microscopy images of freeze fractures of PEKK/unsized CF, PEKK/PEKKo lab‐sized CF and PEKK/PEKKo pilot‐sized CF show that the PEKKo sizing causes an improvement of fiber/PEKK interactions, regardless of the sizing method. Indeed, in both cases, there is a continuity of matter at the interface while we observe a poor wetting of CF by matrix in PEKK/unsized CF. Dynamic mechanical relaxations in shear were analyzed as a function of temperature. The increase of storage modulus upon sizing is observed for both methods but it is more important for PEKKo pilot sizing. In the same way, the mechanical energy loss increases, it reflects the optimization of stress transfer between matrix and fibers

Formulation of Aqueous Dispersions of PEKK by a Quantitative Structure Property Relationship Approach and Application to Thermoplastic Sizing on Carbon Fiberss

The development of formulations for thermoplastic sizing on carbon fibers requires water dispersions of small polymer particles (< 20 µm). PolyEtherKetoneKetone (PEKK) is a high-performance polymer used as a matrix in Carbon Fiber Reinforced Polymers (CFRP) or as a sizing agent. To limit the formulation steps and the use of organic solvents, the sonofragmentation process can be used to deagglomerate polymers, directly in the final aqueous formulation. The sonofragmentation process is controlled by multiple parameters and, in order to identify the key parameters, a quantitative structure property relationship (QSPR) study was performed using artificial neural networks (ANN). The 40 formulations of this study were characterized with the aim of quantifying the sonofragmentation effect. Various physicochemical techniques were used: Photon Correlation Spectroscopy (PCS), destabilization velocity of the dispersions by analytical centrifugation, and scanning electron microscopy. The results obtained showed that only two parameters (mass concentration of surfactant and duration of sonication) had a notable effect on the sonofragmentation process. By controlling these two parameters, it was possible to define a design space in the stability domain of the formulations and to calculate a sonofragmentation efficiency (ϕ) for four singular zones. Image analysis showed that the sonofragmentation process was accompanied by an increase in the number of particles with Particle size (Ps) < 20 µm. In optimized aqueous formulations, the majority of particles should have Ps < 20 µm

Sustainable process for adipic acid production from cyclohexene in microemulsion

Adipic acid appears as an intermediate compound for the synthesis of polyamides and preferentially for the production of nylon-6,6 polyamide. It can be synthesized by the oxidation of cyclohexene by hydrogen peroxide in microemulsion media which has the main advantage to lead a better contact between the two phases thus increasing the yield of the reaction. The microemulsion is generated by stearyl dimethyl benzyl ammonium chloride (C18) as a surfactant avoiding the use of harmful organic solvents and phase-transfer catalysts. The reaction is performed under mild conditions (85 °C, 8 h) with sodium tungstate, - a no heavy metal catalyst - leading to the production of adipic acid in high yield (>80%). By recycling the catalyst and the surfactant, the process becomes truly green