DBD treatment of polyethylene terephthalate: Atmospheric versus medium pressure treatment

In this paper, polyethylene terephthalate (PET) films are modified by a dielectric barrier discharge (DBD) in a helium/air mixture at medium (6.6 kPa) and atmospheric pressure. Surface analysis and characterization of the plasma-treated PET films is performed using contact angle measurements, X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). The polymer films, modified with the DBD at medium and atmospheric pressure, show a significant decrease in water contact angle due to the incorporation of oxygen-containing groups, such as C-O and O-C=O. Results also show that the surface treatment is uniform at micron scales, despite the fact that the discharge consists of a series of microdischarges. It is shown that at low energy densities (< ± 200 mJ/cm²), plasma treatment at medium pressure is more energy-efficient in incorporating oxygen functionalities than plasma treatment at atmospheric pressure. This effect could be induced by the larger diameter of the microdischarges at medium pressure than at atmospheric pressure (factor 3.92) and/or by the lower quenching of atomic oxygen in three-body collisions at medium pressure. The ageing behaviour of the plasma-treated PET films during storage in air is also studied in this paper. XPS results reveal that during the ageing process the induced oxygen-containing groups re-orientate into the bulk of the material. In this paper, it is shown that the ageing behaviour of the PET films is independent of the operating pressure used during plasma treatment.     

Modified Co3O4/ZrO2 catalysts for VOC emissions abatement

The catalytic activity study of cobalt oxides dispersed on different supports evidenced first the highest performances of zirconia based catalysts in the reaction of toluene oxidation. The influence of the presence of ethylenediamine (en) during the preparation of Co/ZrO₂ and the ZrO₂ support modification by Y₂O₃ were then studied and compared with reference catalyst prepared conventionally by impregnation of ZrO₂ with an aqueous solution of Co(NO₃)₂. Addition of an aqueous solution of ethylenediamine to a cobalt nitrate solution led to a strong increase on the catalytic activity of the activated solids in the toluene deep oxidation as compared with the reference catalyst. The best catalytic results were explained in terms of cobalt oxides dispersion but also in terms of Co–support interaction. The generated cobalt species were reducible at much lower temperatures and then were more active in the toluene total oxidation. Finally an efficient catalyst for VOC oxidation was produced combining the modifications of ZrO₂ by yttrium and of the precursor.     

Surface Functionalization with Phosphazenes: Part 6. Modification of Polyethylene-Co-Polyvinylalcohol Copolymer Surface Plates with Fluorinated Alcohols and Azobenzene Derivatives Using Chlorinated Phosphazenes as Coupling Agents

In this paper we describe a two-step surface modification process of poly(ethylene-co-vinyl alcohol) by exploiting hexachlorocyclophosphazene and poly(dichlorophosphazene) as coupling agents. Part of the P–Cl groups of the chlorophosphazenes is first reacted with the surface hydroxylic groups of the substrate to form covalent P–O–C bonds, the remaining being utilized for successive substitution reactions with different nucleophiles (i.e. 2,2,2-trifluoroethanol, heptadecafluorononanol and 4-hydroxyazobenzene). Modified surface properties, such as hydrophobicity improvement with fluorinated alcohols and photochromic features with the azobenzene derivative, were verified by contact angle measurements and UV–Vis spectroscopy, respectively, while changes in surface composition were demonstrated through XPS spectroscopy.     

Study of the ageing behaviour of polymer films treated with a dielectric barrier discharge in air, helium and argon at medium pressure

Plasma treatment of polymers is gaining more and more popularity as a surface modification technique, since it offers numerous advantages over the conventional chemical processes. Plasma surface treatment is an environmentally benign, fast and versatile technology. However, it has one major disadvantage: the induced modification of the surface is not permanent, since the surface tends to recover to the untreated state. This ageing effect is due to the reorientation of induced polar chemical groups into the bulk of the material. In this paper, the ageing of polypropylene (PP) and polyethylene terephthalate (PET) films, treated with a dielectric barrier discharge operating at medium pressure (5.0 kPa) in air, helium and argon, is studied. This study is performed using contact angle measurements and X-ray photoelectron spectroscopy (XPS). Results show that the working gas used during plasma treatment has a significant influence on the ageing behaviour of both PP and PET films. The air-, helium- and argon-plasma treated PP films have a loss in treatment efficiency of 47%, 35% and 25% respectively, while the air-, helium- and argon-plasma treated PET films have a loss in treatment efficiency of 39%, 34% and 29% respectively. These results can be explained by the different cross-linking degrees of the polymer films after plasma treatment. Increasing the cross-linking degree will hinder the movement of the polymer chains and reduce the ageing effect.     

Surface functionalization with phosphazenes. V. Surface modification of plasma-treated polyamide 6 with fluorinated alcohols and azobenzene derivatives through chlorinated phosphazene intermediates

In this article, we describe the synthesis and characterization of surface-modified polyamide-6, using polydichlorophosphazene and hexachlorocyclophosphazene as coupling agents. The solid surface of this polymer was modified first by the introduction of polar functions (CO, OH, OR, COOH, COOR, etc.) with a cold plasma technique, then by the treatment of the alcoholic groups on the surface with (NPCl₂)_n and (NPCl₂)₃ to graft these substrates through the formation of strong covalent P O C bonds, and eventually by the substitution of the residual chlorines on the polyamide-6 surface with different types of fluorinated alcohols (2,2,2-trifluoroethanol and heptadecafluorononanol) and with 4-hydroxyazobenzene. Contact-angle measurements, together with X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy techniques, support the occurrence of these surface-functionalization reactions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Bulk and surface structures of iron doped zirconium oxide systems: Influence of preparation method

Three different Fe-Zr oxide systems were prepared using firstly classical impregnation of iron nitrates on calcined ZrO₂ (Fe_x/ZrO₂, x represents Fe/Zr ratio = 0.01 and 0.11), secondly impregnation of iron nitrates on dried zirconium hydroxide ZrO(OH)₂ (Fe_x/ZrO(OH)₂) and finally hydrolysis of aqueous suspension of iron and zirconium salts to coprecipitate iron and zirconium hydroxides (Fe_x-Zr). Thermal decomposition study of dried samples evidenced a delay in the temperature crystallization of zirconia for Fe_x-Zr and Fe_x/ZrO(OH)₂, the more the iron content in the sample, the more important the delay. For these samples, the formation and the stabilization of different phases were evidenced by several characterization techniques : X-Ray Diffraction (XRD), Raman spectroscopy and Electron Paramagnetic Resonance (EPR).The interaction of iron species with zirconia was different in accordance with different preparations. A bulk dispersion of the coprecipitated sample was observed and as a consequence Zr^{3 +} defects in the solid were not produced. In the case of Fe_x/ZrO₂ sample, production of surface Zr^{3 +} ions was established at low temperature of calcination (up to 600^∘C) and explained by the reaction of NO₃⁻ with Zr^{4 +} on the zirconia surface. However such interaction did not occur for Fe_x/ZrO(OH)₂ since a low dispersion of iron species was observed by X-ray Photoelectron Spectroscopy (XPS), deposited phase (Fe₂O₃) forming preferentially blocks. Temperature Programmed Reduction (TPR) showed that the reduction of small particles of Fe₂O₃ and bulk Fe₂O₃ present in the impregnated samples was easier than that of iron species well dispersed in the bulk of the coprecipitated solid.     

Structural regeneration of LaCoO3 perovskite-based catalysts during the NO + H2 + O2 reactions

In situ X-ray diffraction (XRD) analysis was used to investigate structural evolutions of LaCoO₃ catalysts and then further modified by palladium (Pd) addition, under various controlled atmospheres, particularly during the reduction of NO by hydrogen in lean conditions. Complementary, XPS measurements provided information about changes in the chemical environments of Pd, Co and nitrogen during sequential temperature-programmed reactions. A preactivation thermal treatment under hydrogen led to the destruction of the perovskite structure while in the course of the NO + H₂ + O₂ reactions, the regeneration of the perovskite structure evidenced by XRD at 873 K started at lower temperature (573 K) at the surface. Palladium has been incorporated in order to evidence its effective role in the surface modifications of LaCoO₃ and its consequence on the catalytic activity.     

Effect of spin finish on fiber/binder adhesion in chemically bonded nonwovens

The purpose of this study is to better understand the mechanisms governing the phenomena of fiber/matrix adhesion by controlling the fiber surface properties. This adhesion is evaluated by studying the micromechanical and thermodynamical behavior of the fiber/matrix interface. The complexity of the interactions at the interface requires a global approach that takes into account the chemistry, morphology, and mechanics. The thermodynamical affinity between the binder and fibers is evaluated by the wetting behavior, whereas the mechanical resistance of the fiber/matrix interface is characterized with the pull‐out test. Three distinct approaches are used to classify the different systems according to the nature of the binder and the fiber surface. It is found that there is better adhesion when the spin finish is removed from the fibers, revealing the surface roughness on which the latex can mechanically anchor. © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 4092–4100, 2006     

An in situ study of the NO + H2 + O2 reaction on Pd/LaCoO3 based catalysts

In situ X-ray diffraction (XRD) and quasi in situ X-ray photoelectron spectroscopy (XPS) measurements were complementary used to investigate structural and surface modifications of a palladium-supported on LaCoO₃ perovskite catalyst under various controlled atmospheres, particularly during the reduction of NO by hydrogen under lean conditions, in the presence of a large excess of oxygen.

An extensive reduction of the perovskite was evidenced during the pre-activation thermal treatment of the palladium-supported catalyst under hydrogen at 773 K leading to the formation of Pd particles in contact with Co⁰ and La₂O₃. In the presence of an excess of oxygen, the catalyst structure changes during the reaction. The reduced solid is progressively transformed into LaCoO₃ in the range of 873–1173 K. However, such a bulk transformation probably occurs at lower temperatures at the surface of the solid according to XPS analyses. At the same time, the binding energy (BE) level of the Pd 3d_5/2 photopeak increases up to 337.5 eV which reveals the stabilisation of oxidic palladium species in a different chemical environment than that corresponding to PdO. Such changes induced different catalytic properties of the catalyst during the reduction of NO by H₂.