Plasma treatments pretreatment process

Another effect, "surface contamination", must also be taken into account This may arise from residual gas and small leaks in the vacuum system, but a further possible source should not be overlooked, namely the following Polymers are capable of entrapping appreciable amounts of gas in their free volume, and these molecules are released under the effect of vacuum and of particle bombardment. In the present experiments the polymers were deliberately not degassed before plasma treatment, as such a pretreatment would not likely be economical in an industrial plasma process. The released molecules, primarily air and water vapor, evidently can participate chemically during plasma treatment by intermixing with the feed gas molecules. 

The etch resistance of poly (butene-1 sulfone) in fluorocarbon-based plasmas can be enhanced by prior treatment of the surface in an oxygen plasma. This pretreatment inhibits or retards the depolymerization reaction that characterizes normal etching in fluorocarbon plasmas, thereby permitting formation of a surface-modified layer which exhibits a substantially reduced etch rate. Pretreating PBS in an oxygen plasma enables it to be used subsequently in selective reactive-ion etch processes involving fluorocarbon plasmas to delineate submicron, anisotropically etched patterns. 

These results pointed out the importance of the cathodic plasma treatment of CRS. In order to examine the effect of the pretreatment process on the corrosion performance, two sets of experiments were carried out in which (Ar + H2) plasma treatment time (at a fixed wattage of SOW) and the discharge power (at a fixed treatment time of 12 min) were varied while all other operational parameters were kept constant. The results are shown in Figure 33.6, which clearly shows that the cathodic plasma treatment of CRS is a crucially important factor indicating the importance of the removal of oxides in this interface engineering approach. 

Physical, as well as chemical, pretreatment processes have been combined with the enzyme treatment of wool. A low-temperature plasma is applied to the fibres prior to treatment with polymeric shrinkproofing agent [122]. Combined protease and heat treatment with a saturated steam [123] and the use of high frequency radiation on enzyme treated materials are reported. 

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). 

For the production of polymeric nanocomposites, in many cases a pretreatment and a functionalization of the nanomaterials are necessary [ 13] in order to allow a break up of agglomerates of nanoparticles and to gain adhesion to the matrix and distinct improvement of mechanical properties. This is achieved through various means such as plasma treatment in the presence of certain gasses, which is a well known and widely used process. Various treatments in the liquid phase are also known and applied [7]. 

Polyolefins, such as PE and PP, are commonly used in many applications in the biomedical sector. PE and PP can achieve biocompatible and antimicrobial properties using the suitable surface treatment [131, 132]. Many modification methods of the polymer surfaces have been employed, for example, techniques based on the plasma treatment [133]. A deposition of chitosan on the plasma-pretreated PP surface provides antifungal and antibacterial properties because chitosan exhibits an efficient antimicrobial activity [134]. If PE films were modified by a multistep process using plasma discharge, carboxylic groups and antibacterial agent can be developed over the surface. Immersion of these films into the solution of chitosan leads most likely to the adherence of a chitosan monolayer on the treated film. Small concentration of chitosan was enough for the induction of antimicrobial properties to the modified material [135]. 

Industrial application of plasma treatment for cotton gray fabric pretreatment results in poorer hand feel and sofmess, but these adverse effects can be compensated by the subsequent finishing process. Plasma treatment can reduce effluents and cost of energy compared with conventional pretreatment processes. In terms of energy use, plasma treatment consumes about 9.8 ml of gasoline per meter of fabric while conventional pretreatment method consumes 62.5 ml of gasoline. In addition, the residues that remain after plasma treatment can be removed easily by the subsequent washing process. The plasma treatment shortens the treatment time when compared with conventional pretreatment with chemicals, but similar results can be achieved (Chen, 2005). 

Research on plasma treatment on wool fiber as a pretreatment was started in 1956 (Rakowski, 1997). Plasma-treated wool fiber displays improved antifelting property, dye-ability, and surface wettability. The plasma treatment can alter the surface morphology and chemical composition, but the effect depends greatly on the plasma gas used, system pressure, discharge power, and also treatment lime. Plasma treatment on wool fiber is a dry process in which fiber alteralion is concentrated on the fiber surface and less damage is caused to the bulk fiber. This is a major advantage of plasma treatment on wool fiber. 

Synthetic fibers do not contain natural impurities although there are added impurities such as sizing materials and oil stains. Therefore, their pretreatment process is simpler than other natural fibers. However, synthetic fibers such as polyester and acrylic have poor wettability, dyeability, and antistatic behavior. After plasma treatment, the fiber surface gets physically altered, and hydrophilic functional groups are introduced to the fiber surface, which improves the wettability of the fiber significantly. In recent years, many researchers have studied ways to modify polyester textile materials, and good results have been obtained (Morent et al., 2008). 

Plasma treatment of microchannels can be useful for improving the functionality of microdevices. For example, previous studies have shown that PDMS microchannels can be made hydrophilic by the addition of silane molecules with polar head groups [6]. In this process (3-mercaptopropyl)trimethoxysilane (3-MPS) was absorbed to PDMS to increase the hydrophilic properties of microchannels. Additionally, plasma polymerization has been used to induce in the long-term hydrophilic surface modification by covalently bonding a polymer layer to the surface. Barbier et al. [7] describe a method based on plasma polymerization modification with acrylic acid coatings. First, argon plasma pretreatment was used to activate trace oxygen molecules in the chamber, which partially oxidize the top layer of the substrate. This step cross-linked the surface to reduce ablation of silicon... 

Various surface treatment processes have been developed to ensure adhesion of adhesives, coatings, or print to polymeric surfaces. These treatments are both mechanical and chemical. They include abrasive cleaning, chemical etching, corona discharge, flame treating, plasma treatment, and laser pretreatment. (See also surface treatment.)... 

Studies in the 1990s revealed the good corrosion protection properties of silicon-based plasma polymers on steel substrates and the cmcial influence of the pretreatment process on the stability of the resulting interface [92-101]. The pretreatments for trimethylsilane-based films may consist of an oxidative step (02-plasma) to remove organic contaminations from the substrate and a second reductive step (Ar/H2-plasma) to remove the metal oxide layer. Although the successive application of both steps provides the best corrosion protection of various plasma treatments for steel in combination with a cathodic electrocoat, little is known about the chemical structure of the interface. Yasuda et al. [101] and van Ooij and Conners [97] in particular have shown that the deposition of plasma polymers on steel and galvanized steel might even substitute the chromatation process. 

Analysis of the surfaces generated by these different pretreatment processes [71 ] shows the various surface topographies which are attained (Fig. 23) it is clear how much more efficacious the plasma treatment is. 

The data obtained in the study indicated that the overall effects of the treatment are similar to those observed for certain plasma treatment and flame treatment, even though the actual mechanisms of the surface chemical changes may be different. Unlike glow discharge treatments, the process can be applied under ambient conditions as a continuous treatment method. The data presented indicate that the method may be commercially exploitable for film treatment and further, that the method might be particularly useful for the applications where a controlled level of surface oxidation is required, for example, for surface pretreatment or preparation of delicate films. 

The use of various pretreatments of the plastic wastes such as chemical soaking, heat treatments, microwave, and plasma treatments, etc. in conjunction with the pressurized method might be attractive areas for future research. Co-pyrolysis with other wastes such as food wastes is also plausible. Much work has been carried out on other pressurized carbonization methods such as biomass hydrothermal carbonization [111, 112]. If an industrial process is to emerge from the research, the combined use of various carbon sources would be attractive for economy-of-scale purposes. Producing porous carbons for further applications from plastic wastes would not only yield useful products from cheap precursors, but it would also help reduce the problems associated with the ever-growing plastic waste stream. 

In some cases, in Europe automotive components are pretreated by low-pressure plasma. As this process is more costly than flame treatment, it is used less frequently. However, it is an attractive process for flaming complex parts that cannot be effectively treated due to their size, shape, or the presence of recessed areas. The more consistent plasma process can alter the surface of the entire part and often allows the application of topcoat direct, without the use of and cost associated with a primer. Various systems are offered for plasma treattnent. They mainly differ in the high-frequency wavelength that is used to generate the plasma (10,11). 

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