Plastics plasma treatment

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. 

As an example we present here some computation results for the plasma treatment of the hospital patients room waste with advantage of plastics, cellulose and non-organic metal and glass parts. To check the efficiency of gas fuel generation from this waste we have simulated the limited oxidation within temperature range 1000 - 2500 °C. We have assumed that in 1kg of dry waste are (by weight) 60% of plastics, 15% of silicon glass, and 10% of... 

Some nonconductors, such as the polymers polycarbonates and polystyrenes, must be subjected to a surface treatment prior to activation to ensure good adhesion of palladium nuclei. Surface treatment can include the use of chemical etchants for plastics or reactive gas plasma treatments (66). 

Plasma treatments using various gases can introduce different functional groups to wood surfaces. They may also be used to improve the adhesive properties of plastic coatings. For example, plasma treatments are used industrially as a method of coating automobile bumpers. However, there are some problems in applying plasma treatments to wood. First, the equipment required for plasma treatments is expensive. Second, it is difficult to treat porous woods with plasma under reduced pressures. The latter problem has led to the investigation of normal pressure plasma treatments of wood. 

Kaplan, S. L., and Rose, P. W., Plasma Treatment of Plastics to Enhance Adhesion An Overview, Technical Paper, Plasma Sci., Inc. 

Kaplan, S. L., Plasma Treatment Methods - Preparing Fluoropol5miers for Adhesive Bonding, presented at the Fluoropolymers Div. Meeting, Soc. of Plastics Ind., Amelia Island, FL (Oct. 2, 2001)... 

To avoid this problem plastics are now used rather extensively as carriers for fixed-bed reactors (9,10,12), including denitrification (8). The shape and pore size of plastics can be controlled to give desirable flow characteristics, and the surface can be modified for better microbial attachment, e.g. by plasma treatment. In earlier applications no rigorous conditions or requirements existed for true immobilization of the microbes. Consequently, many cells were detached from the carrier to the effluent causing an increase in the BOD and COD of the effluent water (. ... 

Immobilization of Pseudomonas aeruginosa. Seeking an improvement on some earlier fixed-bed biological reactors, the primary criterion in selecting a plastic carrier was the firm attachment of the microbe to the plastic. This can be achieved if the microbe is either using the plastic as a carbon source and thereby burrows itself into the plastic, or if the plastic surface is treated, e.g., by plasma treatment, to facilitate chemical bonding. 

After screening a wide range of plastic materials, the two most suitable ones were selected polyvinyl chloride (PVC) films and melt blown polypropylene (PP) webs. The softeners in PVC are the carbon source that facilitates firm embedment and continued metabolic activity in long duration continuous operations (20, ). The melt blown PP has an unusually large surface which after plasma treatment has a large capacity for cell loading and very stable holding of bacteria, desirable for heavy metal removal. 

Immobilization of P. aeruginosa on PP. Melt blown, fine PP filaments (jlarge surface area carriers, allowing a high cell loading density (up to a maximum of 1 g cells/1 g plastic). The efficiency of the PP web for bacterial attachment can be greatly enhanced by O2 plasma treatment (wetting) of the surface. 

A decrease in the vs ttability of many hydrophilic fabrics has also been observed by using tetrafluoromethane plasma treatment Okazaki et al. [201] have reported that any desired surface wettability of a plastic surface can be realized by changing... 

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). 

Corona discharge is performed in a high-frequency alternating field (14-40 kHz) at 10 20 kV between two electrodes. The plastic surface is oxidized in a very short period (milliseconds). Plasma treatment is carried out under a moderate vacuum down to ca. 10 Pa. The advantage of this technique is the better penetration depth and the fact that it is also possible to treat shaped parts more easily. The plasma can also burn in gases (e.g., argon), whereby special effects (e.g., plasma polymerization) can be achieved. 

For many industrial applications of plastics that are dependent on adhesive bonding, cold gas plasma surface treatment has rapidly become the preferred industrial process. Plasma surface treatment, which is conducted in a vacuum environment, affords an opportunity to minimize or eliminate the barriers to adhesion through three distinct effects (1) removal of surface contaminants and weakly bound polymer layers, (2) enhancement of wettability through incorporation of functional or polar groups that facilitate spontaneous spreading of the adhesive or matrix resin, and (3) formation of functional groups on the surface that permit covalent bonding between the substrate and the adhesive or matrix resin. Since plasma treatment is a process of surface modification, the bulk properties of the material are retained. The nature of the process also allows precise control of the process parameters and ensures repeatability of the process in industrial applications. Finally, several studies have demonstrated that these surface modifications can be achieved with minimum impact on the environment. 

Plasma treatment of PDMS followed by adsorption of self-assembled silane monolayers has enabled us to controllably modify the surface energy of elastomer surfaces as described in the section on the Johnson, Kendall, and Roberts approach to deriving the surface free energy of solids. A similar treatment of silicon substrates has produced a useful, low—hysteresis model substrate for contact angle study. There are three types of PDMS contact angle substrates usually studied fluids baked or otherwise chemisorbed on solids such as glass or metals cross-linked coatings on flexible substrates, such as paper or plastic film PDMS elastomer surfaces. 

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