Surface treatment of polyolefines by ambient-pressure discharges in N2-H2 mixtures - steps towards a new perspective
Coating and Surface Technology
Chemical and Thermal Process Engineering
Polymer Materials
Final Report Abstract
We were able to demonstrate that the chemical derivatization of polymer surfaces plasma treatment in nominally oxygen-free gases such as N2, N2-H2, and NH3, respectively, using aromatic aldehydes and carboxylic acid anhydrides is not a viable method on which quantitative analyses with respect to concentrations of amino groups may be based. In addition to primary amino groups (aldehydes) or primary and secondary amino groups (anhydrides) these reagents are able to react also with other N- bearing functional groups, for example imines. The presence of such groups on plasma-treated surfaces or in plasma-deposited thin films can not be excluded a priori. In fact, evidence has been presented that substantial amounts of C=N groups are present on the surfaces studied in this project. While our studies were focussed on plasma-treated polymers, there are several strong arguments for the presence of large amounts of imines in N-rich plasma polymers as they have been studied by several groups since more than a decade. Nevertheless, the presence of these moieties has generally been ignored in the analysis of such films which was generally based on a combination of XPS with chemical derivatization by aldehydes and anhydrides. The main conclusion from our project for futures studies is the there is a strong need of alternative analytical methods for nitrogen-bearing plasma-treated polymers and plasma-deposited thin films. Chemical derivatization with electrophilic and nucleophilic reagents will keep a value as a routine tools to assess the overall chemical reactivity of such materials. However, because plasma-generated materials generally contain so far unknown moieties with unknown reactivity, physical analytical methods such as FTIR spectroscopy or NEXAFS will have to be applied in order to reveal their true chemical composition.
Publications
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Chemical derivatization and chemical nature of polymer surfaces treated in afterglows of N2-H2 DBDs, 8th International Conference on Reactive Plasmas / 31st Symposium on Plasma Processing, Fukuoka, Japan, 2014
C.-P. Klages, Z. Khosravi
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In-situ FTIR spectroscopic studies of DBD-based polymer surface nitrogenation, 14th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XIV), Zinnowitz, Germany, 2014
C.-P. Klages, Z. Khosravi
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Nucleophilic derivatization of polyethylene surfaces treated in ambient-pressure N2–H2 DBD post discharges, Plasma Chem. Plasma Process. 34, 661-669 (2014)
Z. Khosravi, C.-P. Klages
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On the chemical nature of polymer surfaces treated by DBDs in N2-H2 mixtures, 1st Sino-German Symposium on "Atmospheric Pressure Gas Discharges and Plasma Applications", Beijing, PR China, 2015
C.-P. Klages
