Treatment plasma treatments

Figure 10.8 Temperature dependence of the magnetization for the Sn Fe Q.gN], sample prepared by plasma treatment. Plasma treatment conditions Chy-N.-H (molar ratio = 1 1 4), 2.7 X 102 Pa, 723 K, and 2 h.24...

Plasma treatment involves the production of chemically active species and ultra-violet radiation. Conventional methods of surface modification are often limited by the temperature needed for surface treatment, the leaching or toxicity of chemical agents used, and the spectral and geometric limitation of UV treatments. Plasma treatment also provides a means of selectively modifying the surface while the bulk properties remain generally unaffected ( ). 

Figure 30.21 Schematic presentation of the difference in the structures of modified surface treated by plasma treatment and LTCAT treatment plasma treatment tends to modify the fragmented polymers while LTCAT treatment tends to strengthen the top layer.

The hydrophobic effect on a woven cotton fabric can be obtained by surface treatment. Plasma treatment with acid as a component of original gas will result in a hydrophilic surface [66]. 

Many pretreatment techniques are used in practice (Table 8.2). The normal physical method used to improve the adhesive strength of the coating to the substrate is to slightly roughen the surface by solvent treatment, abrasion, or blasting. Some plastics (e.g., polyolefins) require special pretreatment methods processes that modify the surface molecular layers of the plastic to increase their polarity have proved suitable (e.g., flaming, immersion in an oxidizing acid, immersion in a benzophenone solution with UV irradiation, corona treatment, plasma treatment). 

The nonwoven polyolefin fabric is used. The thickness of the separator is 100-200 pm, and the basis weight of the fiber is 50-80 g/m. The hydrophilicity is provided to the fiber surface of the separator with the sulfonation treatment, plasma treatment or acrylic acid graft polymerization treatment. 

Flame treatment (polymer) A method of oxidizing the surface of a polymer web to increase its surface energy by subjecting it to a flame in air. See also Corona treatment Plasma treatment. 

R. Manory and A. GriU, Protective Coatings of Metal Sufaces by Cold Plasma Treatments, NASA Technical Memorandum 87152, National Technical Information Service, Springfield, Va., 1985. 

Surface Modification. Plasma surface modification can include surface cleaning, surface activation, heat treatments, and plasma polymerization. Surface cleaning and surface activation are usually performed for enhanced joining of materials (see Metal SURFACE TREATMENTS). Plasma heat treatments are not, however, limited to high temperature equiUbrium plasmas on metals. Heat treatments of organic materials are also possible. Plasma polymerization crosses the boundaries between surface modification and materials production by producing materials often not available by any other method. In many cases these new materials can be appHed directly to a substrate, thus modifying the substrate in a novel way. 

M. D. Smith, Suface Modfcation of High-Strength Reinforcing Fibers by Plasma Treatment, AUiedSignal Inc., Kansas City, Mo., July 1991, p. KCP-613-4369. 

W. Rakowski, Plasma Treatment of Wool, PhD. dissertation, PoUsh Textile Institute, Lodz, 1991 idem, Pr. Inst. Wlok. 36—37, 184—201 (1987) K. M. Byrne, Finishing of Wool using Plasma Technology, IWS Technical Information Bulletin CPB 109, International Wool Secretariat, Tikley, U.K., (1991). 

The principal problems for sdicone mbber as a viable lens material are the nonpolar nature, which gives Hpid deposits and wettabdity problems and the tendency to adhere to the cornea. Efforts to modify the sdicone lens surface for improved wettabdity have achieved limited success. These efforts include grafting hydrophilic monomers, such as HEMA, GM (150), and NVP (151—153), to the lens surface and plasma treatments of finished lenses. Efforts to improve the movement of sdicone lenses on the cornea with various lens designs have not been successfld, and the cause of lens—cornea adherence, which is not an exclusive problem of sdicone lenses, is an active area of research. 

Surface modification of a contact lens can be grouped into physical and chemical types of treatment. Physical treatments include plasma treatments with water vapor (siUcone lens) and oxygen (176) and plasma polymerization for which the material surface is exposed to the plasma in the presence of a reactive monomer (177). Surfaces are also altered with exposure to uv radiation (178) or bombardment with oxides of nitrogen (179). Ion implantation (qv) of RGP plastics (180) can greatiy increase the surface hardness and hence the scratch resistance without seriously affecting the transmission of light. 

After deposition of 0.5 nm of copper onto plasma modified polyimide, the peaks due to carbon atoms C8 and C9 and the oxygen atoms 03 and 04 were reduced in intensity, indicating that new states formed by the plasma treatment were involved in formation of copper-polyimide bonds instead of the remaining intact carbonyl groups. Fig. 28 shows the proposed reaction mechanism between copper and polyimide after mild plasma treatment. 

Negative TOF-SIMS speetra of PMDA/ODA polyimide before and after plasma treatment are shown in Fig. 53. The speetra generally show inereas-ing fragmentation as a function of plasma treatment time. This tendency was especially evident for the peak at m/z = 215 (PMDA + H ). 

Fig. 53. Negative TOF-SIMS spectra of PMDA/ODA polyimide (a) before plasma treatment and after plasma treatment for (b) 1 s and (c) 60 s. Reproduced by permission of John Wiley and Sons from Ref. 33).

While polymeric surfaces with relatively high surface energies (e.g. polyimides, ABS, polycarbonate, polyamides) can be adhered to readily without surface treatment, low surface energy polymers such as olefins, silicones, and fluoropolymers require surface treatments to increase the surface energy. Various oxidation techniques (such as flame, corona, plasma treatment, or chromic acid etching) allow strong bonds to be obtained to such polymers. 

Wertheimer, M.R., Martinu, L., Klemberg-Sapieha, J.E., and Czeremuszkin, G., Plasma treatment of polymers to improve adhesion. In Mittal, K.L. and Pizzi, A. (Eds.), Adhesion Promotion Techniques — Technological Applications. Dekker, New York, 1999, pp. 139-174. 

Gas plasma treatment operates at low pressure and relatively low temperature. While the corona treatment is applicable to substrates in sheet or film form, the gas plasma process can treat objects of virtually any shape. The gases most widely used to generate plasma by free-radical reactions include air, argon, helium, nitrogen, and oxygen. All these, with the exception of oxygen. 

Brosse et al. [41] modified isotactic polypropylene and other polyolefins by a cold plasma. In isotactic polypropylene, plasma treatment results in a polypropylene crystallization of paracrystalline or smectic form into a a-crystalline form. Further, the active films are susceptible to react with monomers in a postgrafting reaction. 

Electric discharge (corona, cold plasma) is another method of physical treatment. Corona treatment is one of the most interesting techniques for surface oxidation activation. This process changes the surface energy of the cellulose fibers [28]. In the case of wood surface activation it increases the amount of aldehyde groups [291. 

---