Ethylene plasma-polymerization rates

Equation (12.7) relates p to p, but both constants c and d contain parameters for the monomer and the product gas. Therefore, it is anticipated that Eq. (12.7) would hold between p and but that the intercept and the slope of a straight line would depend on the pumping characteristics of the monomer. Figure 12.3 depicts the p -pa relationship for the plasma polymerization of ethylene with and without a liquid N2 trap in the system. Although there exists a relationship given by Eq. (12.7), cannot be uniquely related to / o- In other words, the manipulation of by manipulation of the pumping rate does not control the value of p ... 

The rate of plasma polymerization depends on the nature of the monomer gas. In addition, such parameters as flow rate, pressure, power, frequency, electrode gap and reactor configuration also strongly influence the polymerization rate for a given monomer. Generally at low flow rates there is an abundance of reactive species so the polymerization rate is limited only by the availability of monomer supply. At high flow rates, however, there is an overabundance of monomer concentration and the polymerization rate now depends on the residence time. At intermediate flow rates these two competing processes result in a maximum. This behavior is illustrated in Figure 1 for ethane, ethylene, and acetylene (11). These data also demonstrate the effect of increased unsaturation in... 

Figure 1. Rates of plasma polymerization of acetylene, ethylene, and ethane as a function of monomer flow rate (llj...

Figure 5. The rate of plasma polymerization of ethylene as a function of electrode gap (15)...

Most studies of plasma polymerization have been conducted in continuous wave rf plasmas. The effects of pulsed mode operation have received only limited attention. In a recent study, Yasuda et al. (1 ) found that while the polymerization rate of most monomers decreased when polymerization was carried out in a pulsed versus continuous plasma, the polymerization rate of a few monomers was enhanced. The present study was undertaken to determine the effects of pulsed operation on the plasma polymerization of ethylene and ethane. These monomers were selected because their behavior in continuous wave plasmas had been examined extensively in previous investigations (2 - ). ... 

As in the case of ethylene and acetylene W, plasma polymerization of benzene produced either a powder or film depending on reaction conditions. A typical condition in which thin film with the required property was produced (the RO membrane condition) is shown in Table 1, coded as Condition B, while that for poor quality film formation is designated A. Conditions for powder formation are designated C and E in the table. Generally speaking, film formation was observed at high benzene flow rates, and powder formation was observed at low pressures and low benzene flow rates, as in the case of ethylene and acetylene ( ). However, the RO membrane conditions do not correspond to either a unique point on the pressure (P) versus benzene flow rate (Q(Bz)) plane nor do they correspond to the conditions in which a lot of polymer was produced. This means that the quality of the film cannot be correlated directly to the macroscopic reaction conditions. 

Tubular blood-contacting polymeric materials were modified by plasma polymerization and evaluated in animals (baboons) with respect to th r c iadty to induce acute and chronic arterial thrombosis. Nine plasma polymers based on tetrafluoro-ethylene, hexafluoroethane, hexafluwoethane/H, and methane, when deposited on silicone rubber, consumed platetets at rates ranging from l.l-5.6x 10 platelets/on day. Since these values are close to the lower detection limit for this test system, tl plasma polymers were considered relatively nonthrombogenk. Thus, artificial blood tube made of polyesters, having the inner side coated with plasma-pcrfymerized tetra-fluoroethylene, is now commercially available. 

Figure 2.3 IgG levels after administration of drug delivery systems in rats. Controlled-delivery systems for antibody class IgG. The insert figures show the release of antibody from the delivery system during incubation in buffered saline. The panel (a) inset shows release from poly(lactic acid) microspheres these spherical particles were 10-100/rm in diameter. The panel (b) inset shows release from a poly[ethylene-co-(vinyl acetate)] matrix these disk-shaped matrices were 1 cm in diameter and 1 mm thick. In both cases, molecules of IgG were dispersed throughout the solid polymer phase. Although the amount of IgG released during the initial 1-2 days is greater for the matrix, the delivery systems have released comparable amounts after day 5. (a) Comparison of plasma IgG levels after direct injection of IgG (open circles) or subcutaneous injection of the IgG-releasing polymeric microspheres characterized in the inset (filled circles). The delivery system produces sustained IgG concentrations in the blood [3]. (b) Comparison of plasma IgG levels after direct intracranial injection of IgG (open squares) or implantation of an IgG-releasing matrix (filled squares) [4]. The influence of the delivery is less dramatic in this situation, probably because the rate of IgG movement from the brain into the plasma controls the kinetics of the overall process.

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