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  • 1
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Plasma desorption time-of-flight mass spectrometry (PD-TOFMS) using accelerated argon ions (9 MeV) has been successfully used for characterizing the surface modifications induced at the surface of poly(ether etherketone) (PEEK) by cold plasma treatments. While the intact polymer structure leads to the emission of negative ions from fragmentation of the repeat unit, the degradation of such a structure under plasma exposure gives rise to production of oxidized fragments. It is demonstrated that this production is highest for a plasma using a mixture of O2 and N2 (20:80), and that as a function of treatment duration, the rate of oxidation of the modified surface layer correlates with adhesive strength, at least in a first step. PD-TOFMS is used for analysis of the failure patterns of epoxyamine adhesive/PEEK/carbon composite in order to localize the fracture position. It is concluded that the increase of the cohesion of the interphase layer as a function of the plasma treatment duration leads to a shift from the interphase/PEEK interface to the bulk of the matrial.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The plasticization of a glass/epoxy unidirectional composite by water has been investigated by Dynamic Mechanical Thermal Analysis (DMTA). The analysis of the thermomechanical spectra of the water aged material revealed the apperance of a splitting of the tan δ peak associated with the α transition. This splitting was found to be dependent on the experimental conditions, i.e., the temperature scan rate, the straining frequency, and the initial water content on the composite. A thermogravimetric analysis (T.G.A) of the wet specimens has shown that this effect could be attributed to an enhanced drying of the specimens above the glass transition, during the DMTA temperature scan. A differential plasticization of the epoxy network at the aging temperature can therefore not be invoked from the appearance of a splitting of the DMTA spectra. In conditions where the sample drying was minimized, plasticization effects on the thermomechanical properties of the composite were found to be temperature independent and reversible after re-drying of the aged material. Owing to the filling of hygrothermally induced cracks with water, the composite sensitivity to plasticization can be underestimated significantly at elevated aging temperature.
    Additional Material: 10 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zur Verbesserung der Adhäsionseigenschaften von Polypropylenfilmen für unter Vakuum aufgebrachte dünne Aluminiumschichten wurde die Polymeroberfläche durch Einwirkung von Mikrowellenplasma unterschiedlicher Art und Zusammensetzung modifiziert. Die Konzentration der in der Probenumgebung befindlichen Spezies wurde mit der Emissionsspektroskopie bestimmt. Die Eigenschaftsänderungen der Polymeroberfläche wurden mittels ESCA und durch Messung der Kontaktwinkel an polaren und unpolaren Flüssigkeiten untersucht. Die Adhäsionseigenschaften wurden im Pull-off-Test ermittelt. Die Verbesserung der Benetzungsfähigkeit ist auf die Bildung einer sehr dünnen, teilweise methanollöslichen Oberflächenschicht mit Carboxy- und Ethylenfunktionen zurückzuführen, wie die ESCA-Analyse ergab. Benetzung und Adhäsion hängen von der Zusammenseztung des verwendeten Gasgemisches ab und nehmen mit steigendem Anteil an atomarem Sauerstoff zu, der bei der Entladung erzeugt und in der Nachentladungsphase vom Gasstrom weggespült wird. Zwischen den im Pull-off-Test ermittelten Haftspannungswerten und den während des Rückgangs der Benetzung gemessenen Werten der polaren Wechselwirkung wurde eine Beziehung hergestellt.
    Notes: In order to improve the adhesion properties of polypropylene on a thin aluminium layer deposited under vacuum, a superficial modification of the polymer has been carried out by exposing the polymer surface to a microwave plasma from gas of different nature and composition.The concentration of the present species in the sample proximity (downstream) has been measured by emission spectroscopy.Superficial polymer modifications have been analysed by ESCA and by measuring contact angles with polar and apolar liquids. The adhesion measurements have been performed by pull-off tests.The wettability increase has been attributed to the creation of a very thin superficial layer which is partially soluble in methanol and includes carboxylic and ethylenic functions being observed by ESCA.Wettability and adhesion depend on the composition of the gas mixture used. They increase with the atomic oxygen quantities which are created in the discharge and carried away in post-discharge by the gas flow. A relationship has been established between the tensile stress values obtained by the pull-off test and the polar interaction values measured during dewetting.
    Additional Material: 11 Ill.
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  • 5
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polypropylen wurde mittels Gasentladung unter niedrigem Druck behandelt. Die Oberflaäachenmodifizierung wurde durch ESCA-Analysen, Messungen der Benetzbarkeit und Adhäasionsunterschungen in Abhäangigkeit von der Behandlungszeit und der Art des verwendeten Gases (Luft oder Argon) charakterisiert. Die Ergebnisse von “advancing”- und “receding” -Kontaktwinkelmessungen mit Wasser (sehr polar) und Diiodmethan (unpoler) in einem automatischen dynamischen Tensiometer ziegen eine Zunahme der Benetzbarkeit nach der Oberfläachenbehandlung. Dier wird auf die entstehung hochenergetisch polarer Stellen auf der Oberfläache zuräuckgefäuhrt. Die ESCA-Analyse belegt, daß die modifizierte Oberfläahe aud niedermolekularem Material besteht; sie ist in Methanol läolich.Die Adhäsion von Aluminium an der Polypropylen-Oberfläche wird bereits durch eine wenige Sekunden dauernde Gasentladungsbehandlung verbessert. Sie hängt von der polaren Komponente der Oberflächenenergie des Polymeren ab.
    Notes: Low-pressure discharge treatments were applied to the surface of polypropylene. ESCA analyses, wettability measurements and adhesion tests were carried out to characterize surface modifications as a function of treatment time and nature of gas (air or argon). Advancing and receding contact angles were measured with an automatic dynamical tensiometer. The liquids used were water (very polar liquid) and methylene iodide (apolar liquid). The results show an increase in wettability by the surface treatment. This is due to the creation of high-energy polar sites. ESCA analysis also shows that the modified surface layer is soluble in methanol and is made up of low-molecular-weight material.Adhesion of polypropylene/aluminium is also increased by the low pressure discharge treatment from the few first seconds of the treatment. This adhesion increase is a function of the polar component of the polymer surface energy.
    Additional Material: 7 Ill.
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