Michel Sclavons

Quantification of the maleic anhydride grafted onto polypropylene by chemical and viscosimetric titrations, and FTIR spectroscopy

An acid-base titration method for an accurate and reproducible quantification of maleic anhydride grafted onto polyolefins is proposed. The use of an organic base (tetra-butylammonium hydroxide) enhances the base solubility in organic solvents and prevents phenomena like coarcervation. The titration goes on until the visual endpoint of a coloured indicator, corresponding to the neutralisation of the grafted functions. Bromothymol blue is chosen as the coloured indicator to determine this equivalence point. It is critically correlated with a Fourier transform-infrared spectroscopy quantification developed previously by De Roovers et al. [J Polym Sci, Part A: Polym Chem 1995;33:829] and with a viscosimetric titration method here-proposed Finally, the titration mechanism is confirmed by the titration of some well-defined amount of anhydride model compounds and by FTIR analyses of their products after titration

The anhydride content of some commercial PP-g-MA: FTIR and titration

A set of anhydride-grafted polypropylenes was collected from various companies. They were studied in light of our recent results on polypropylene melt grafted with maleic anhydride.(1) This work confirmed that an important decrease of the anhydride content is recorded on heating or washing, due to the elimination of free, ungrafted products, respectively, by sublimation of maleic anhydride and by polymaleic anhydride solubilization. The deconvolution of the infrared spectra of washed anhydride-grafted polypropylenes (PP-g-MA) revealed two types of grafted anhydride: succinic anhydride form and polymaleic anhydride form. All in all, four forms of anhydride functions were detected: two grafted and two free, each being either on monomeric or polymeric forms. Nevertheless, one PP-g-MA (Hercoprime) can be distinguished by its very high grafting level. This polymer is therefore discussed in more detail. Finally, all the present results are discussed with regard to the principal applications of the PP-g-MA as a blend compatiblizer or as an adhesion promoter

Sizing Removal and Functionalization of the Carbon-fiber Surface Studied By Combined Tof Sims and Xps

Time-of-flight secondary ion mass spectrometry (TOF SIMS) and X-ray photoelectron spectroscopy (XPS) have been jointly used to study a two-step surface processing of AS4 carbon fiber: extraction of sizing in CH2Cl2 and functionalization with trimellitic anhydride. The combined information on molecular specificity obtained with TOF SIMS and quantification obtained with XPS allows us to follow qualitatively and quantitatively the changes in functional groups on the carbon surface. The results show that the sizing on AS4 contains at least four different compounds. These compounds can be extracted in CH2Cl2 and the elimination is almost complete for silicone. The functionalization of AS4 with trimellitic anhydride has been realized. The reaction takes place between the amine groups on the carbon fiber and the two types of functional groups in trimellitic anhydride.

Supported dynamic mechanical thermal analysis: an easy, powerful and very sensitive technique to assess thermal properties of polymer, coating and even nanocoating

A dynamic mechanical. thermal analysis (DMTA) performed on stacked coated supports or on samples sandwiched between rigid supports (carbon or glass fibers, metal or glass plates, ...)is described. The choice of a dual cantilever deformation favors the shear strain of the less stiff material between the more rigid supports. A theoretical model demonstrates that the less stiff material response is mainly recorded and moreover amplified. An exceptional sensitivity to the soft material is therefore observed. This method does not require any special sample (only stacking of coated supports or sample sandwiching) whilst it enables to characterize in situ polymer coating, even nanocoating. This characterization is of prime interest in technological coating developments such as paints, fiber sizings, glues, ... This possible measurement of thermal transitions peculiar to nanocoatings also opens more fundamental studies as the probing of interface influence on thermal transitions

Elaboration of poly(lactic acid)/halloysite nanocomposites by means of water assisted extrusion: structure, mechanical properties and fire performance

Poly(lactic acid) (PLA)/halloysite nanotube (HNT) nanocomposites were prepared using a water assisted extrusion process. Morphology, structure, thermomechanical properties and flame retardant properties of these nanocomposites were compared to those obtained in the case of nanocomposites obtained via the conventional extrusion process. Whatever the synthesis route used, mechanical tests indicate that HNTs have a reinforcing effect ascribed, at least partially, to the dispersion of the HNTs in the PLA matrix. Differential scanning calorimetry also shows that HNTs improve PLA crystallization and play the role of a nucleating agent. Moreover, cone calorimeter experiments show a drastic improvement in the reaction to fire of PLA when HNTs are added, especially at high filler content. This improvement arises from the fact that HNTs induce the formation of a protective inorganic layer at the surface of the sample. As the main results of this study, it has been shown that water assisted extrusion not only induced a better dispersion of the HNTs into the matrix but also that this process prevents polymer degradation during the extrusion. This unusual effect has been ascribed to a barrier effect of the water molecules that preferentially locate at the HNT–matrix interface. Even if not fully explained, it could be ascribed to a decrease in local shear levels (mechanochemical effect) and/or to a decrease in the catalytic effect of the HNT surface (chemical effect). Consequently this study reveals that water-assisted extrusion is a reliable route to prepare PLA/halloysite nanocomposites with enhanced properties.

Fast separation of the three main plasma lipoprotein classes by ultracentrifugation using vertical rotor and multiple discontinuous density gradient

An ultracentrifugation technique for isolation of the various lipoprotein fractions using a vertical rotor is described. By the use of a multiple discontinuous density gradient, very low density lipoproteins, low density lipoproteins and high density lipoproteins are sharply separated, without contamination of other lipoproteins or albumin. Centrifugation time is 80 min. The densities, electrophoretic mobilities, electron microscopic appearance and chemical composition are those of the expected classes of lipoproteins. Two different gradients are used to enhance the separation of very low density lipoproteins from low density lipoproteins on one hand and high density lipoproteins from infranatant on the other.

Use of An Internal Standard To Assay 6 Beta-hydroxycortisol in Urine

Abstract Currently 6 β-hydroxycortisol is assayed by radio-immunoassay or high performance liquid chromatography techniques. We have developed an HPLC method, utilizing gradient elution and an internal standard {a 4-pregnene-tetrol-3-one}. In this way, accuracy and sensitivity of the assay were greatly improved and allowed the application of this modified method for monitoring the time-course of hepatic microsomal enzyme activity.

Highly loaded nanocomposite films as fire protective coating for polymeric substrates

The main fire retardancy mechanism of polymer–clay nanocomposites involves the progressive build-up of an inorganic-rich layer at the sample surface during combustion, by a combination of ablative reassembling and migration of the nanoparticles, reducing heat and mass transfer between gas and condensed phases. In this process, a non-negligible amount of polymer needs to be sacrificed before the entire surface of the residual material is shielded. This study aims to improve the fire behaviour of polymer–clay nanocomposites by accelerating the physical barrier formation through the development of new hybrid structures. For that purpose, a system based on polyamide 12 and halloysite nanotubes is chosen as reference and highly loaded nanocomposite films are coated on a virgin PA12 substrate. Both the influence of clay fraction in the nanocomposite film and its thickness on the flammability performance of the coated samples are evaluated by mass loss calorimetry and compared to that of homogeneous ‘bulk’ nanocomposites. Results show unambiguously that hybrid materials are more effective than conventional nanocomposites to flame retard polymers while substantially reducing the total filler loading, and so the cost of the final product. Moreover, a small amount of carbon nanotubes can be incorporated in the polymer substrate and/or in the nanocomposite film to suppress the vigorous bubbling of evolved degradation products as well as to reduce the flexibility of the thin protective skin, which can cause detrimental effects on its barrier properties.

Hplc With Uv-vis Spectrophotometric Detection for Blood and Tissue Drug Assays

SummaryExperience in blood and tissue drug assays by means of HPLC with UV-VIS detection is reported. More than 20 drugs or their analogues, which belong to many different therapeutic classes, are analyzed with a limited number of columns and of eluents (isocratic mode). A simple device to warm a reverse-phase column has also been tested. The guidelines applied here will be of interest to people who want to simplify the analysis of a wide range of drugs.

Using water to modify the localization of clay in immiscible polymer blends

Bio-based polyamide 11 (PA11) and water-soluble polyethylene oxide (PEO) (80/20 wt/wt) were used to prepare an immiscible polymer blend. Ternary systems containing 1 wt% hydrophilic clay (organomodified or native clay) were elaborated using extrusion with and without injection of water. The cryoscopic effect on PA11 and PEO observed by high pressure differential scanning calorimetry indicated that they were both miscible with water under conditions of water-assisted extrusion. Transmission electron microscopy revealed a selective localization of both types of clay in the matrix (PA11). However, with water-assisted extrusion a part of the organomodified clay platelets was localized into the dispersed phase (PEO). Under rheological tests, the unmodified clay exhibited a different effect compared with the organomodified clay on the modulus and viscosity of the blend. The van Gurp–Palmen plot indicated that clay potentially decreased the interfacial tension between PA11 and PEO, while the weighted relaxation spectra confirmed that water improved the dispersion state of the clay and limited the polymer degradation. Thermogravimetric analyses showed that the presence of clay and water improved the thermal stability of PA11/PEO blends. Our work is the first one which has realized water-assisted extrusion of a clay-filled ternary blend.