Plasma treatment surface modification techniques

Figure 2 presents the most common plasma-based surface modification techniques for biomedical applications, described in more detail later plasma assisted chemical vapor deposition or PACVD (RF, MW), physical vapor deposition or PVD (sputtering, cathodic arc), plasma polymerization and grafting, plasma-based thermochemical treatments (e.g. plasma nitriding), ion implantation, plasma immersion ion implantation or PHI, and plasma spraying. Each technique has unique advantages and applications, and the choice of the more adequate technique often depends on the... 

FIGURE 23.2 Surface modification techniques of electrospun nanofibers, (a) Plasma treatment or wet chemical method, (b) Surface graft polymerization. (c) Coelectrospinning. Reprinted with permission from Ref. [43]. Copyright 2009. Elsevier. 

Plasma treatment is one of most common and suitable surface modification techniques for polymeric materials. This treatment can selectively introduce certain functional groups at a polymer sur ce with little damage to the bulk of the polymer. However, it is known that a plasma-treated polymer surface loses its properties gradually with aging. One reasonable explanation for this phenomenon is that the nctional groups, introduced by plasma treatment, rotate or move away from the surface into the bulk. Thus the changing surface properties may reflect... 

Other surface modification techniques include the use of free radical-, photochemical-, radiation- redox- and plasma-induced grafting. These are used to covalently attach some useful monomers onto the membrane surface [20]. Gas plasma treatment is also used to induce surface modification water permeabihty is improved by oxygen plasma treatment due to the introduction of hydrophihc carboxylate groups, whereas argon plasma treatment can enhance chlorine resistance by increasing the extent of cross-linking at the nitrogen sites. 

A wide array of surface modification techniques, ranging from simple to sophisticated, wet to dry, and vacuum to nonvacuum, are available for a host of polymeric materials. They include plasma surface treatment laser surface treatment corona, flame, UV, ozone, UV/ozone, photochemical, photografting, chemical grafting, and chemical methods of stuface modification and modification of polyamide surfaces by microorganisms [7]. 

Based on the membrane surface properties and the HA properties, various researchers have attempted to change the membrane surface characteristics by surface modification. Different techniques have been performed, such as ion beam irradiation, plasma treatment, redox-initiated graft polymerization, photochemical grafting, and interfacial polymerization (IP). In this chapter, two surface modification techniques, IP and photochemical grafting, are discussed by means of experimental examples. The surface characteristics of the unmodified membrane and the modified membranes are studied and their relationships with irreversible fouling and NF performance are reported. 

Air or argon plasma treatment has been widely used as a facile surface modification technique for many biomaterials since its surface hydrophilicity can be easily increased with this treatment. Yoon et al. (2009) investigated the preparation and... 

Surface modification techniques these can include such approaches as the laser ablation of the surface using, for example, excimer lasers. Other possibilities are to use plasma, corona and flame treatments to modify the laminate surface, chemically, to make it more amenable to adhesive bonding. As for thermoplastic matrices, it should be possible to introduce highly polar groups onto the surface to improve bonding across the interface. 

Another issue, which is only briefly mentioned in this Chapter, is the use of cold plasma for surface modification of conventional materials. We can thus improve the properties of "conventional" elements relevant to the construction of electrochemical cells electrode substrates, electrodes themselves, separators, etc. Research interest in this field of the cold plasma technology is comparable to that which is focused on entirely new materials produced by plasma deposition techniques. The use of the plasma treatment technique in... 

Polypropylene (PP) is, besides polyesters, one of the most widely used polymers for producing synthetic fibres, especially for technical applications. PP fibres are mostly used in different technical fields due to their excellent mechanical properties, high chemical stability and processability. However, because of low surface energy, lack of reactive sites and sensitivity to photo- or thermal oxidation the polymer properties are insufficient for some applications. Therefore, several techniques for fibre modification have been reported, e.g. plasma treatment, chemical modification and nanomodification, i.e. production of nanocoated and nanofilled materials. 

Surface modification techniques used to charge the substrates on which the nanolayers are to be deposited can be categorized as physical or chemical. Chemical modification techniques include surface patterning, photobleaching or plasma treatment. Methods of physical modification primarily... 

In a previous section, the effect of plasma on PVA surface for pervaporation processes was also mentioned. In fact, plasma treatment is a surface-modification method to control the hydrophilicity-hydrophobicity balance of polymer materials in order to optimize their properties in various domains, such as adhesion, biocompatibility and membrane-separation techniques. Non-porous PVA membranes were prepared by the cast-evaporating method and covered with an allyl alcohol or acrylic acid plasma-polymerized layer the effect of plasma treatment on the increase of PVA membrane surface hydrophobicity was checked [37].The allyl alcohol plasma layer was weakly crosslinked, in contrast to the acrylic acid layer. The best results for the dehydration of ethanol were obtained using allyl alcohol treatment. The selectivity of treated membrane (H20 wt% in the pervaporate in the range 83-92 and a water selectivity, aH2o, of 250 at 25 °C) is higher than that of the non-treated one (aH2o = 19) as well as that of the acrylic acid treated membrane (aH2o = 22). 

The surface analytical techniques mentioned above provide wealth information on the composition and structure of polymer surfaee and changes resulting from modification by plasma discharge. It should be however stressed that, despite of broad spectrum of analytical techniques available, the information is not sufficient to understand all imderlying proeesses in their eomplexity. Espeeially, it is the case of plasma treatment when the interaetions of many plasma eonstituents with polymer surface may play a role. Existing theoretical models are restricted to some specific cases and they usually deseribe only some part of the proeess. 

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