Plasma treatment of polymer surfaces

Polymer substrates are often coated with metals for a wide variety of reasons. In many cases, the chemical condition of the surface has been found Q) to alter the adhesion of the metal film to the substrate. In particular, oxygen plasma treatment of polymer surfaces before metal deposition has been found (, 4)... 

Plasma treatment of polymer surfaces can result in surface texturing and the improved adhesion strengths can then be attributed to mechanical interlocking. This texturing may be accompanied by changes in the surface chemistry due to changes in the termination species. 

The parameters of treatment were chosen since these led to the most pronounced changes of polymer surface in our previous experiments [70-74]. It was observed elsewhere that plasma treatment of polymer macromolecules results in their cleavage, ablation, alterations of chemical structure and thus affects surface properties e g. solubility [75]. The chemical structure of modified polyethylene (PE) was characterized by FTIR and XPS spectroscopy. Exposition to discharge leads to cleavage of polymeric chains and C-H bonds followed by generation of free radicals which easily oxidize [10,76]. By FTIR spectroscopy the presence of new oxidized structures within whole specimen volume can be detected. IR spectra in the 1710-1745 cm" interval [71,77] from PE, exposed to... 

Jang, B.J., Das, H., Hwang, L.R., Chang, T.C. (1988). Plasma treatments of fiber surfaces for improved composite performance. In Proc. ICCI-II, Interfaces in Polymer. Ceramic and Metal Matrix Composites (H. Ishida ed.), Elsevier Sci. Pub. New York, pp. 319-333. 

Table 7.21 Effects of Plasma Treatment on Polymer Surface Modification...

New catalysts of hydrogen oxidation for low-temperature fuel cells are molybdenum and tungsten carbides [2, 3], For solid polymeric fuel cells the novel catalysts by plasma treatment of polymer membrane have been developed. The radicals at surface are generated. These radicals are catalysts of anodic reactions [4]... 

Static secondary ion mass spectroscopy (SSIMS) ranks with XPS as one of the principal surface analytical techniques. Treatment of polymer surfaces to improve their properties with respect to wetting or water repulsion and to adhesion, is by now a standard procedure. The treatment is designed to change the chemistry of the outermost groups in the polymer without affecting bulk properties. One popular surface treatment is plasma etching. The use of SSIMS is most amenable to the surface evaluation of such treated materials. 

Plasma (partially ionized gas) can be utilized to alter the surface characteristics of polymers by (1) exposing a surface of polymer to non-polymer-forming plasma (e.g., O, N, H2O, Ar, He, etc.) or by (2) depositing very thin layer of plasma polymer on a surface of polymer. Both processes can produce significant changes on the surface properties of polymers and can contribute to the improvement of wear resistance of polymers, since many changes which can be related to the wear resistance of polymers generally start to take place at the polymer surface. Fundamental aspects of plasma treatment of polymers and plasma polymerization are reviewed. 

The most important result of the plasma treatment of polymers, which are produced on an industrial scale, is the change in their wettability and adhesion characteristics. As was discussed earlier, plasma treatment can make polymers more lydrophilic as well as more hydrophobic. Both effects are widely used for practical applications. The change of wettability is usually characterized experimentally by the contact angle 9, which is formed on the solid surface along the linear solid-hquid borderline of air (see Fig. 9-25). An increase of... 

The most widespread methods to manufacture the PHB scaffolds for tissue engineering by means of improvement of cell adhesion and growth on polymer surface are change of PHB surface properties and microstructure by salt-leaching methods and enzymatic/chemical/physical treatment of polymer surface [40, 89, 98, 113]. Adhesion to polymer substrates is one of the key issues in tissue engineering because adhesive interactions control cell physiology. One of the most effective techniques to improve adhesion and growth of cells on PHB films is the treatment of polymer surface with enzymes, alkali, or low-pressure plasma [40, 113]. Lipase treatment increases the viable cell number on the PHB film from 100 to 200 times compared to the untreated PHB film. NaOH treatment on PHB... 

The type of information provided by the techniques listed in the tables also varies greatly. Many spectroscopic techniques give qualitative and/or quantitative elemental composition. The vibrational techniques, however, generally provide information on the molecular structure. SIMS, especially in the static mode (SSIMS or TOFSIMS), can yield information on molecular structures and even orientation of monolayers [5-10]. This is particularly useful for the study of the absorption of coupling agents on metals or to determine the effects of plasma treatments on polymer surfaces [11]. TOFSIMS instruments also have capabilities for determining the two-dimensional distributions of elements or molecular species at the surface, similar to the capabilities (for elements only) offered by AES and EDXA or WDXA. 

P Wittenbeck and A Wokaun, Plasma treatment of polypropylene surfaces Characterization by contact-angle measurements , J. Appl. Polym. Sci, 1993 50 187. 

Corona and plasma treatments of polymers modify otily the near-surface region of the material leaving bulk properties completdy unaffected. This type of "surface engineering" constitutes a very powerful tool for the devdopers of new materials, for example of polymer matrix composites, as we have tried to illustrate in fois text on hand of numerous examples. 

During plasma treatment of polymers, bonds may be broken at both ends of small segments of polymer chains and organic fragments will be released into the boundary layer over the surface. These fragments will react, either with other free radicals in the boundary layer, or with the VUV flux. In either case, in an O2 plasma, they decompose towards the ultimate by-products of CO, CO2, and H2O. However, in the process of this decomposition many transient species are formed that greatly complicate the chemistry of the boundary layer. It is these species that react with the polymer surface and that will interfere with the diffusion of active species from the plasma to the polymer surface. 

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