Marie-Georges Olivier

Eugenol-based benzoxazine: from straight synthesis to taming of the network properties

Mixed benzoxazine precursors were synthesized using a blend of eugenol, a natural renewable product, and phenol. The structures of these mixed benzoxazine precursors with different phenol:eugenol compositions were attested by 1H NMR. Their polymerization and degradation were investigated and monitored by DSC and TGA and showed an enhancement of the crosslinking ability with the phenol content. Depending on its relative content, the phenol moiety proved to limit the thermal degradation of the bis-benzoxazine “hybrid” monomer and allowed the formation of crosslinked networks with high thermomechanical stabilities. The properties of the networks were closely dependent on the phenol:eugenol ratio, which allowed for adjustment of the crosslinking density and fine tuning of the glass transition temperature (Tg) within a wide temperature range. A comparison between the polymerized hybrid precursors and blend of two pure monomers displaying the same overall composition showed the same material properties increasing the tunability of the system. The eugenol/phenol combination for the preparation of mixed/hybrid benzoxazines or corresponding blends clearly paves the way to new sustainable high performance bio-based materials.

High-refractive-index transparent coatings enhance the optical fiber cladding modes refractometric sensitivity

The high order cladding modes of standard single mode optical fiber appear in quasi-degenerate pairs corresponding to mostly radially or mostly azimuthally polarized light. In this work, we demonstrate that, in the presence of a high-refractive-index coating surrounding the fiber outer surface, the wavelength spacing between the orthogonally polarized cladding modes families can be drastically enhanced. This behavior can be advantageously exploited for refractometric sensing purposes. For this, we make use of tilted fiber Bragg gratings (TFBGs) as spectral combs to excite the orthogonally polarized cladding modes families separately. TFBGs were coated with a nanometer-scale transparent thin film characterized by a refractive index value close to 1.9, well higher than the one of pure silica. This coating brings two important assets: an ~8-fold increase in refractometric sensitivity is obtained in comparison to bare TFBGs while the sensitivity is extended to surrounding refractive index (SRI) values above 1.45.

Free radical-induced grafting from plasma polymers for the synthesis of thin barrier coatings

Plasma polymer films (PPF) are attracting a great deal of attention for application in various fields due to several remarkable properties, such as good adhesion to different substrates, improved mechanical/chemical stability and a high surface reactivity. This reactivity, associated with the presence of free radicals and originating from the PPF growth mechanism based on many fragmentation and recombination reactions, is often, however, a potential source of trouble. Oxidation of the PPF promptly begins in aerobic conditions via reactions of surface free radicals with oxygen molecules and causes a deterioration of its intrinsic properties in the surface region leaving a nonspecifically functionalized surface in the long-term. Recently a novel approach to functionalize plasma polymer films through the grafting reaction initiated from free radicals trapped on the PPF surface was developed. The present work investigates the potential to employ such an approach in a corrosion protection context. Characterization methods, including Electrochemical Impedance Spectroscopy (EIS) tests, demonstrate that the controlled consumption of surface free radicals via polymer grafting, instead of oxidation, has a beneficial effect on the corrosion protection behavior of the PPF layer deposited on clad 2024 aluminum alloy.

Use of Electrochemical Impedance Spectroscopy (EIS) for the Evaluation of Electrocoatings Performances

Thanks to their barrier properties against corrosive species, organic coatings are often used to protect metals against corrosion. In the automotive industry, cathodic electrocoating is widely used as a primary layer coating in the corrosion protection system [1-3]. This deposition method has many advantages including high throw power, high corrosion protection and coating transfer coefficient (>95%), auto-limitation of the coating thickness, environmentally friendly due to an aqueous suspension medium and an easy industrial automation [4, 5]. This coating can also be applied on each metal composing the car body.

Adsorption of propane, propylene and propadiene on activated carbon

Abstract Four adsorption isotherms at 278, 288, 293 and 303 K of propane, propylene and propadiene on activated carbon are given. The results at pressures up to 0.9 P P s are obtained using an automated apparatus and correlated by the vacancy solution model of Suwanayuen and Danner.

Mild steel corrosion in chloride environment: effect of surface preparation and influence of inorganic inhibitors

Abstract The aim of the present work is to study the effect of surface mild steel preparation on its electrochemical behaviour in neutral chloride solution without and with an inorganic inhibitor. Various surface preparations are examined: alkaline degreasing, acid pickling and polishing. Open circuit potential measurements and potentiodynamic polarisations are used as corrosion monitoring techniques. The effect of chloride concentration is evaluated. The ability of inorganic inhibitors (Na2MoO4, NaNO2, Na2WO4 and Na2VO3) to stabilise the passive state of steel in chloride containing solutions is assessed by electrochemical and surface analysis techniques. The results reveal that, among the four inhibitors studied, the sodium molybdate is the best environmentally friendly corrosion inorganic inhibitor for steel.

Automatic measurement of isotherms of adsorption on microporous media in large ranges of pressure and temperature

In this paper, we present an automatic apparatus for measurement of adsorption of gases on microporous media at constant temperature. Our method is based on a static volumetric method. This apparatus allows one to obtain adsorption isotherms in the ranges 0-4000 kPa and 273-373 K. This wide range of pressure allows one to reach saturated pressure for many gases and to study capillary condensation when the pressure tends to the saturated pressure. Software developed in our department controls the electrovalves and carries out temperature and pressure measurements. Characteristic isotherms are presented of adsorption of ethane on activated carbon at 278 and 303 K in the range 76-3607 kPa.

Arbutin-based benzoxazine : en route to an intrinsic water soluble biobased resin

A novel benzoxazine monomer containing a carbohydrate moiety was synthesized using a solventless approach from the reaction of arbutin, a naturally occurring phenolic compound, furfurylamine and formaldehyde. The chemical structure of this fully bio-based benzoxazine monomer was confirmed by 1H NMR and FTIR. Its polymerization has been investigated and monitored by DSC showing the ring opening polymerization of benzoxazine functions with a network densification thanks to the reaction of the furan group. The high hydroxyl content of the monomer allows its easy solubilisation in water paving the way to a wide range of possible “environmentally friendly” applications especially in the fields of coatings, paintings and adhesives.

A multilayer coating with optimized properties for corrosion protection of Al

In the context of a universal search for alternatives to chromate-based coatings, which are toxic for both human beings and the environment, a multilayer coating for Al protection purposes is developed and investigated in the current work. The first layer is selected to be a hexamethyldisiloxane-based plasma polymer film (PPF), deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD), due to a number of interesting features that are characteristic of plasma polymers. The second layer is synthesized via the polymerization of the 2-ethylhexyl acrylate monomer initiated from the free radicals trapped on the surface of the PPF during its growth. A subsequent layer of a copolymer of 2-ethylhexyl acrylate and glycidyl methacrylate, poly(EHA-co-GMA), is deposited by spin coating to increase the corrosion resistance of the coating. An improvement in the anti-corrosion properties of the multilayer coating by approximately three orders of magnitude as compared to the uncoated Al substrate is observed. Further enhancement of the adhesion and scratch resistance properties is addressed via UV-crosslinking and the incorporation of in situ generated silica nanoparticles into the final layer.

Influence of sol–gel application conditions on metallic substrate for optical applications

Abstract An efficient energy management of a building requires optimum use of the light energy, which is strongly dependent on optical properties of used materials. In the lighting sector, aluminium is generally employed as substrate for the reflectors. Nowadays, new steel substrates combining good corrosion resistance and flexibility are developed to answer the growing need of this market. Specific requirements for optical applications are a high reflectivity (total reflectivity >82%), a high superficial hardness and durability and also a suitable formability. The sol–gel layer is used in this particular application for its levelling properties before depositing of the reflective layer and good barrier properties to avoid contact between the metallic layers. The corrosion protection and the barrier properties of the sol–gel layer are investigated as a function of the thickness. The protection conferred by the sol–gel layer on stainless steel substrate is studied by the electrochemical measurements in a sodium chloride solution (electrochemical impedance spectroscopy and polarisation curves). The stress generated in the layer is determined versus temperature, humidity and hygrothermal conditions.