Discharge/plasma treatments

Rajanikanth, B.S., Srinivasan, A.D. and Ravi, V. (2005) Discharge plasma treatment for NOx reduction from diesel engine exhaust A laboratory investigation, IEEE Trans. Diel. El. Insul. 12, 72-80. 

Cao L, Sukavaneshvar S, Ratner BD, Horbett TA. Glow discharge plasma treatment of polyethylene tubing with tetraglyme results in ultralow fibrinogen adsorption and greatly reduced platelet adhesion. Journal of Biomedical Materials Research A 2006,79,788-803. 

Surface ozone oxidation is applied in polymers because it has the following advantages it introduces peroxides uniformly on the polymer surfaces it is applicable to complex geometries it can be handled easily and it is relatively economical as compared with other techniques such as corona discharge, plasma treatment, flame treatment, irradiation with gamma rays.I 1... 

Removal of a-Pinene from Air Using Pulsed Corona Discharge Plasma Treatment of Exhaust Gas Mixtures... 

Figure 1.10 Typical setup for discharge/plasma treatment of a polymeric surface. Reprinted from [49] with permission.

Hiroshi U, Kogoma M, Okazaki S. Atmospheric pressure glow discharge plasma treatment method. Japan Patent No. 4-344250 issued Dec 24, 1992. 

Roth JR, Tsai P, Liu C, Wadsworth LC. Method and apparatus for glow discharge plasma treatment of polymer materials at atmospheric pressure. US Patent No. 5456972 May 28, 1993. 

Leroux F, Campagne C, Perwuelz A, Gengembre L. Polypropylene film chemical and physical modifications by dielectric barrier discharge plasma treatment at atmospheric pressure. J Colloid Interface Sci 2008 324 412-20. 

Some polymers have very low surface energies (like polyethylene or polytetrafluoroethylene), and they require surface preparation to raise the surface energy. This can be done through chemical treatment, corona discharge, plasma treatment, flame treatment, and ultraviolet radiation [9]. 

Plasma Arc Treatment - In adhesive and solvent bonding, a method for treating the surfaces of parts prior to solvent and adhesive bonding, in which an electrical current between two electrodes in a gas at low pressure exeites the gas particles, producing free radicals. Contaminants are stripped from the surface of the part, and wettability is increased by reduction of the contact angle. Also ealled plasma discharge, plasma treatment. See also Corona Discharge Treatment... 

Effect of Atmospheric Glow Discharge Plasma Treatment on CO2 Permeability and Chemical Structure of Poly(dimethylsiloxane) Membranes... 

It could be argued that, in spite of the exeellent results seen when using corona discharge, plasma treatment and laser ablation surfaee pretreatment techniques, it is unlikely that they will be cost effective and will be difiheult to introduce for the treatment of large components. However, in view of the poor performances now often seen by using conventional abrasion techniques, it is probable that ways round these difficulties will have to be found. 

Demidouk, V., Ravi, V., Chae, J.-O. et al. (2005) Pt-Al203 catalyst and discharge plasma pre-treatment techniques for enhancing selective catalytic reduction of nitrogen oxides A comparative study, React. Kinet. Catal. Lett. 85, 239-44. 

A disadvantage with conventional plasma treatment techniques is the requirement for treatments to take place in a vacuum, adding to the equipment costs. However, if a dielectric material is placed between the electrodes of the plasma equipment, then treatment can be performed at atmospheric pressure. This method is known as a dielctric barrier discharge treatment and has been the subject of some recently reported studies. 

Gluing is difficult, needing pre-treatments such as, for example, chemical etching (sulfo-chromic acid etching), flame oxidation or hot-air (500°C) treatment, corona discharge, plasma or UV treatments. The exposure must be brief and superficial and the original and aged properties must be tested. 

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. 

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... 

Figure 13. Concentration depth profile of oxygen incorporated in HOPE and LDPE modified in the Ar plasma at the discharge power of 1.7 W. The numbers are the times of plasma treatment in seconds. The profiles were determined by RBS technique [70].

Figure 16. Dependence of the PE contact angle on the exposure time to 8.3 W plasma discharge. The contact angle was measured at different times elapsed from the plasma treatment. The numbers are the times in hours elapsed from the plasma treatment [71].

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