Plasma polymerization reactor for

Fig. 5 Schematic representation of the tumbler RF plasma reactor for plasma polymerization onto...

Fig. 6 Schematic representation of the vertical tubular reactor for plasma polymerization onto powders [41]...

Figure 3.3. Tubular reactor for plasma polymerization. (Reproduced with permission of the author.)...

A tjqrical reactor for plasma polymerization imder reduced pressure is shown in Figure 26 [47]. However, modem developments in plasma polymerization enable a stable plasma even at atmospheric pressures. Details of the mechanisms of plasma polymerization can be foimd in Ref 45. Organic precursors. 

Fig. 1. Reactors used for plasma polymerization a bell jar b rectangular flow channel c electrode-less...

The ACTIS process described above is a typical example of low-pressure plasma polymerization or LCVD, which is an ultimate green process with no effluent in the practical sense. Microwave plasma is used for plasma polymerization of acetylene. ACTIS process, as an example of LCVD, has an ideal combination of unique advantages in (1) very high reaction yield (monomer to coating), (2) no effluent from the process, (3) no reactor wall contamination because the reactor wall is the substrate surface, and (4) very short reaction time. However, whether such an ideal LCVD process is an industrially viable practice is a totally different issue. 

Unexpected elements in a plasma polymer often are due to the redeposition of ablated materials. The presence of nitrogen found in a plasma polymer of a monomer that does not contain nitrogen can be traced to contamination of the reactor, which has been used for plasma polymerization of nitrogen-containing monomers [1]. The ablation of electrode material has been utilized to create a graded metal-polymer and polymer-metal interfaces to obtain an excellent adhesion [2,3]. Ablation, therefore, could be utilized in a beneficial way in the engineering of interfaces if we know the nature of ablation and how to control it. 

Because solid materials must maintain the vacuum, the reactor wall always exists in an LCVD reactor. The plasma also interacts with wall materials as well as any other materials that exist in the plasma, such as substrate and support. Therefore, polymer-forming intermediates and gaseous by-products may also originate from solid materials with which plasma interacts by virtue of the ablation caused by the luminous gas. In this sense, any material that interacts with plasma becomes a source of monomer for plasma polymerization. 

The measurement of pg requires a pressure transducer system that is not influenced by the electric power used for the plasma polymerization, particularly when a high-frequency radio frequeny power is employed. Some pressure transducers that give pressure readouts independent of the nature of a gas are ideally suited for plasma polymerization. Some electronic gauges the readout of which depends on the nature of the gas (e.g., thermal conductivity) do not provide accurate readings of Pg because in most cases the composition the gas mixture in the LCVD reactor is unknown and there is no way to calibrate the meter for an unknown gas mixture. 

A bell jar type of reactor used for plasma polymerization usually employs a set of parallel electrodes, and the glow is more or less confined to the space between the electrodes. In such a system, the total volume of the reactor is considerably larger (e.g., more than a factor of 10) than the plasma volume. A reactor that consists of a large tube and a pair of electrodes located inside can also be considered a bell jar type of reactor. In other words, whether a bell jar or a vessel of another shape is used is not a major issue. 

In a batch operation, substrates are placed in a reactor, and plasma polymerization coating is carried out as a unit operation. Repeating the same operation treats a large number of substrates. The batch processing is the primary mode for nearly all laboratory-scale operations. The batch processing can be done in a closed system or in a flow system. Because the number of molecules in a reactor under low pressure is small, it is often necessary to use a flow system to obtain a sufficient amount of coating. 

Another illustrative example of the application of FTIR spectroscopy to problems of interest in adhesion science is provided by the work of Taylor and Boerio on plasma polymerized silica-like films as primers for structural adhesive bonding [15]. Mostly these films have been deposited in a microwave reactor using hexamethyldisiloxane (HMDSO) as monomer and oxygen as the carrier gas. Transmission FTIR spectra of HMDSO monomer were characterized by strong... 

Plasma polymerization is usually carried out in a low pressure glow discharge sustained by either a dc or an ac electric field. Examples of the reactors used for this purpose are shown in Fig. 1. The simplest configuration involves a pair of circular parallel plate electrodes mounted inside a glass bell jar. The lower electrode usually serves as the substrate holder and is sometimes heated or cooled. Monomer is introduced through a feed tube and unconsumed monomer and gaseous products are withdrawn through a port in the base plate. 

Plasma Polymerization. Plasma-induced polymerization (24) of vinyl monomer from inorganic particles is also employed for polymer grafting. The conventional reactors for liquid-phase polymerization of vinyl compounds after generation of plasma on inorganic particles or powders have been recently invented by Ikeda et al. (25). Haraguchi et al. (26) have also prepared polymer-modified silica by plasma-induced polymerization of glycidyl methaciylate. 

The hydrodynamic factors that influence the plasma polymerization process pose a complicated problem and are of importance in the application of plasma for thin film coatings. When two reaction chambers with different shapes or sizes are used and when plasma polymerization of the same monomer is operated under the same operational conditions of RF power, monomer flow rate, pressure in the reaction chamber etc., the two plasma polymers formed in the two reaction chambers are never identical because of the differences in the hydrodynamic factors. In this sense, plasma polymerization is a reactor-dependent process. Yasuda and Hirotsu [22] systematically investigated the effects of hydrodynamic factors on the plasma polymerization process. They studied the effect of the monomer flow pattern on the polymer deposition rate in a tubular reactor. The polymer deposition rate is a function of the location in the chamber. The distribution of the polymer deposition rate is mainly determined by the distance from the plasma zone and the... 

The plasma polymerization onto silica was carried out after charging 100 g of dried silica Ultrasil VN3 into the reactor, pumping down to 13 Pa and introducing plasma gasses or monomer vapors for further plasma polymerization. The conditions for the preparation of plasma-polymerized acetylene (PA), pyrrole (PPy) and thiophene (PTh) are presented in Table 2. 

For measuring the Al-polymer (PP) peel strengths the plasma polymerization was performed using the previously described reactor. Then, the plasma polymer coated polymer samples were transferred into a separate electron beam metallizer (Auto 306, Edwards, UK). The thickness of deposited aluminium layers was adjusted to 150-200 nm using a quartz microbalance. The metal peel-... 

In the middle of a spectrum, the gain in one feature is attained on sacrifice of another feature. Therefore, one must choose a plasma polymerization process, including type of reactor, reaction conditions, and type of monomer (starting gas or vapor), aimed at a specific type of plasma polymer i.e., type A or type B, suitable for an application. 

It is also important to recognize the domain in which a plasma polymerization is carried out under a given set of operational conditions. The value of WjFM alone does not identify whether a plasma polymerization is in the energy-deficient or the monomer-deficient region. A crude estimate of the domain might be made by the parameter WjFM)la( if the value of a were known for the reactor. The following conditions can be used for this purpose ... 

An example of plasma copolymerization of gases is the incorporation of N2 in the plasma polymer of styrene. N2 mixed with styrene was consumed in plasma polymerization [12]. In a closed-system experiment, pressure measurement is a very useful tool for investigating plasma polymerization, particularly when the monomer used does not produce gaseous by-products. The pressure changes observed in a closed-system plasma reactor with mixtures of N2 and styrene are shown in... 

The inclusion of particles in a film of plasma polymer was once considered by some investigators to be a characteristic problem due to the plasma polymerization mechanism, which hampers the practical use of plasma polymers in some applications. In contrast to this view, the formation of powder or the inclusion of particles in a film is related to the polymer deposition part of polymerization-deposition mechanisms. The inclusion or elimination of particles, therefore, could be accomplished by selection of the proper operational parameters and reactor design. The data of Tiepins and Sakaoku [7] are a typical demonstration that powders can be formed nearly exclusively if all conditions are selected to favor powder formation. An important point is that the monomers used in their study were those commonly used by other investigators for the study of film formation by plasma polymerization in other words, no special monomer is needed to form powders exclusively. 

The effect of reactor size on the deposition characteristics was investigated by comparing deposition rate profiles of plasma polymerized perfiuoropropene films in three reactors of different size. The local deposition rates were measured at various operating conditions (combinations of three monomer pressures and three discharge powers), which are listed in Table 19.1. Deposition rate profiles along the reactor tube in three reactors are shown in Figures 19.2, 19.3, and 19.4 for the corresponding... 

According to this scheme of plasma polymerization of TMS in a closed system, it is anticipated that the atomic composition of the plasma polymer should continuously change with the plasma polymerization time. Figure 13.21 depicts comparison of XPS cross-section profile of C/Si ratios for plasma polymers deposited in a flow system reactor and that in a closed system reactor. The results clearly show that a closed system plasma polymerization of TMS indeed produces a... 

Contact lenses are coated with an approximately 20-nm-thick layer of a methane-based plasma polymer by a continuous mode operation, which is shown schematically in Figure 36.2. The total processing time for a contact lens is approximately 40 min, which includes drying wet contact lenses before plasma polymerization coating, evacuation, LCVD, and repressurizing for sample removal. The coating operation could be continuous for approximately 30 days between maintenance breaks. The reactor is capable of coating 30 million contact lenses a year (340 days of operation). 

---