Glow discharge polymers, plasma

Decay Rate of Cathodic Plasma Polymer and Glow Discharge Polymer... 

Using the aluminum sheet substrate as the cathode of a direct current (DQ glow discharge, cathodic plasma polymerization is carried out. Dealing with metal surfaces, cathodic plasma polymerization is the most practical means to provide the best corrosion protection (see Chapter 13). A primer is applied on the surface of the plasma polymer. The thickness of the plasma polymer is roughly 50 nm on average and that of the primer layer is about 30,000 nm (30 pm). Primers used included E-coat (electrolytic deposition of paint) and spray primers, but no top coat was applied in the study of corrosion protection. 

Resistance of polymers to ozone attack is studied in space environments in actual applications. In the laboratory, glow discharge or plasma etching is the common method for laboratory study of ozone effect. Plasma and low earth-orbit environments are not equivalent. For instance, oxygen plasma contains a variety of other particles including electrons and free radicals in addition to atomic oxygen. In contrast, atomic oxygen is the dominant constituent of low earth-orbit. 

The formation of polymeric materials in the plasma state of organic vapor(s) (partially ionized state) is referred to as plasma polymerization, and the resultant materials are plasma polymers. Because the most practical way to create low temperature plasma is to employ an electric glow discharge, the terms glow discharge polymerization and glow discharge polymers are often used synonymously for plasma polymerization and plasma polymers. 

Fabrication of polymers for these small and integrated sensors should be by the new processing technologies, which can produce accurate, mass reproducible and thin polymers. The polymers fabricated by conventional methods may have potential problems such as the difficulty of preparing thin (<1 pm) and homogeneous films. A plasma-polymerised film offers a new alternative [19]. The plasma-polymerised film is achieved in a glow discharge or plasma in the vapour phase. Such films are thin (< 1 pm), pinhole-free, flat-surface structures and are chemically and mechanically stable. 

Photopolymerization and Plasma Polymerization. The use of ultraviolet light alone (14) as well as the use of electrically excited plasmas or glow discharges to generate monomers capable of undergoing VDP have been explored. The products of these two processes, called plasma polymers, continue to receive considerable scientific attention. Interest in these approaches is enhanced by the fact that the feedstock material from which the monomer capable of VDP is generated is often inexpensive and readily available. In spite of these widespread scientific efforts, however, commercial use of the technologies is quite limited. 

Poljraer surfaces can be easily modified with microwave or radio-frequency-energized glow discharge techniques. The polymer surface cross-links or oxidizes, depending on the nature of the plasma atmosphere. Oxidizing (oxygen) and nonoxidizing (helium) plasmas can have a wide variety of effects on polymer surface wettability characteristics (92). 

Mass spectrometer studies of oxidant additions to fluoro- and chlorocarbon gases have demonstrated that the relative reactivity of atoms with unsaturate species in a glow discharge follows the sequence F -- O > Cl > Br (41), Of course, the most reactive species present will preferentially undergo saturation reactions that reduce polymer formation and that may increase halogen atom concentration. Ultimately, determination of the relative reactivity of the plasma species allows prediction of the primary atomic etchants in a plasma of specific composition. 

Glow discharge or "cold" plasmas are gaining increased currency for the deposition of novel and potentially valuable macromolecular coatings. The range of properties attainable by a plasma-polymer is wide, and depends critically on such variables of the plasma deposition process as choice of monomer, substrate temperature (T ), power density (p), the excitation frequency (v), and others incluSing monomer flow rate, reactor geometry, etc... Control over these variables can produce crossllnked, dense deposits which adhere tenaciously to... 

Plasma polymers are deposited on surfaces in contact with a glow discharge of organic or organometallic monomers, in the form of a thin film and/or as a powder. Such films find applications as surface modifiers and in applications where the bulk properties of extremely thin films are desirable. 

For most practical coating processes, the monomer flows into a plasma reactor with a continuous glow discharge, and is wholly or partially consumed in the conversion to plasma polymer. In such a setup, gaseous by-products and unconverted monomer are continuously pumped out of the reactor. 

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