Plasma polymerization coating characteristics

Similar to static contact angles from the sessile droplet method, Wilhelmy dynamic contact angles are an excellent indication of the change in surface characteristics due to surface modification techniques such as plasma polymerization coating. The cosine of dynamic advancing contact angles from the first immersion, cos 0D,a,i of untreated, TMS-treated, and (TMS-I-02)-treated conventional... 

Type A plasma polymers have the characteristic internal stress built in the film, and the plasma polymerization coating acts as the tempered ultrathin layer on the substrate. The internal stress is caused by the wedging effect of the deposition process, and the total stress increases linearly with the thickness. As the thickness increases, the internal stress reaches the critical point beyond which the internal stress becomes greater than the cohesive force or the adhesive force of the plasma polymerized coating. Above the critical thickness, therefore, the coating cracks (not necessarily in macroscopic sense) or delaminates (buckles) from the substrate. Consequently, there exists a thickness limit of plasma polymerization coating. The tighter the structure, the smaller is the thickness limit. 

Plasma polymers of certain kinds of monomers have very little, if any, internal stress, and thickness is not a limiting factor of application. However, because of this very feature such polymers may not provide certain coating functions that are sought for the application of plasma polymerization. In other words, the internal stress is not a drawback of plasma polymer but an important characteristic of the materials formed by LCVD. 

Considering the fact that the refractive index continues to increase after most of the polymerizable species are exhausted in the gas phase, DC LCVD of TMS in a closed system contains the aspect of LCVT of once-deposited plasma polymer coating by hydrogen luminous gas phase. In the later stage of closed-system LCVD, oligomeric moieties loosely attached to a three-dimensional network are converted to a more stable form, and significantly improved corrosion protection characteristics (compared to the counterpart in flow system polymerization of TMS) were found, details of which are presented in Part IV. Thus, the merit of closed-system cathodic polymerization is well established. 

LPCAT polymerization or coating could be considered more or less the same as the plasma polymerization or coating by other conventional plasma processes, except that the kinetic pathlength of growth is short. The ultrathin layers prepared by LPCAT polymerization have the general characteristics of plasma polymers, i.e., amorphous (noncrystalline), high concentration of the dangling bonds (free radicals... 

When an organic vapor, such as methane, in low pressure (e.g., less than 1 torr) is subjected to an electromagnetic field, the electrical breakdown of the gas occurs, yielding a glow the color of which is characteristic to the gas. In the luminous gas phase, methane is activated and forms a polymeric deposition in the form of a coating on the surface of substrate placed in the glow. This process is termed plasma polymerization because the luminous gas phase or glow indicates the presence of plasma, and the process does not proceed without plasma. The strict definition of plasma is (at least partially) ionized gas, which maintains the electrical neutrality as a whole. The luminous gas phase in which plasma polymerization takes place, however, is not plasma in the strict sense. 

The use of thin films derived from chlorotri-fluoroethylene as optical device protective coatings has been reported (100,101). Not only do the films protect the moisture sensitive substrates from atmos-phereic humidity but they also exhibited antireflection properties. Reis, et. al. (102) and Hiratsuka, et. al. (103) explored the use of plasma polymerized ethane as protective coatings for laser windows. The absorption and antireflection characteristics of these coatings were reported. 

A capacitively coupled reactor designed to permit continuous coating of a moving substrate with plasma polymer has been described [ 1 ]. In this paper the results of a study of the plasma polymerization of tetrafluoroethylene in such a reactor presented. Plasma polymer has been deposited on aluminum electrodes as well as on an aluminum foil substrate placed midway between electrodes. The study particularly explores conditions in which deposition is minimized on the electrode. For this reason the chemical nature of the polymer formed in a low flow rate (F = 2 cm (S.T.P.)/min) and low pressure (p = 60 mlllltorr) plasma has been analyzed by the use of ESCA (electron spectroscopy for chemical analysis) and deposition rate determinations. This method combined with the unusual characteristics of TFE plasma polymerization (described below) has yielded Information concerning the distribution of power in the inter-electrode gap. The effects of frequency (13.56 MHz, 10 KHz and 60 Hz), power and magnetic field have been elucidated. The properties of the TFE plasma polymer prepared in this apparatus are compared to those of the plasma polymer deposited in an inductively coupled apparatus [2,3]. 

In view of these potential advantages, the process of plasma polymerization was adapted to coat microsphere targets. A special device for exposing the microspheres to obtain a uniform coating was devised. A major problem which was solved was the elimination of rough surfaces characteristic of these coatings. 

Films fabricated with the plasma polymerization technique have various advantageous characteristics, such as a flawless thin coating, good adhesion to the substrate, mechanical toughness, and thermal stability, and therefore they have a wide variety of potential applications. 

As far as black-dyed fabrics are concerned, the blackness of SN-2000 has been manifested its excellent characteristics for a use in the black formal wears, and been modified with coating a resin of low refraction rate besides, this blackness has been by far upgraded by a thin film on the surface, nearly lOOnm thick, which the plasma polymerization method could just feature by this method, SN-2000 successfully provided the coal-blackness which any natural fiber has not ever been able to offer, and has outdone a level of natural fibers. 

Several studies have presented the results of plasma polymer characterization by various techniques 3 - s - 52 such as i.r., wettability, and adhesion characteristics. The wettability properties of plasma-polymerized styrene films were dependent upon the degree of incorporation of N into the film. Severe polymerization conditions (high power, low pressure) resulted in a reduction in aromaticity of PP films. The electrical properties of certain plasma polymers were reported. Experiments to optimize coating parameters for the continuous coating of a moving substrate have been carried out. The reactivity of plasma polymers... 

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