Parylene polymers

There have been several parylene polymers deposited using CVP. Essentially, they are all derivatives of paraxylylene. The unsubstituted... 

In contrast to the above situations, parylene polymer deposition has very poor adhesion to a smooth surface substrate but can penetrate deep into small cavities. para-Xylylene prefers to react with another para-xylylene or its derivatives. Although it has the feature of difunctional free radical, it is rather stable and does not initiate polymerization of other monomers for conventional free radical polymerization. In spite of numerous attempts, the polymerization of various vinyl monomers initiated by para-xylylene or copolymerization of vinyl monomers with /7ura-xylylene has been elusive. 

Parylene polymer deposition has very poor adhesion to a smooth-surface substrate. A freestanding... 

However, the poor adhesion of the surface does not allow a further painting stage. The surface of Parylene coatings can be modified by a special plasma coating. In this way, an interlayer is placed to provide good adhesion to the substrate as well as to a subsequent primer. After this procedure, the hydrophobic Parylene polymer again becomes paintable with both solventborne and waterborne spray primers." ... 

To protect the reflective layer from exposure to the ambient atmosphere, corrosive substances, salt, humidity, etc., a Parylene polymer protective layer is used. A cross section through a fiber optic waveguide is shown in Figure 2.5. The fiber optic waveguide comprises a ... 

Parylene polymer protective layer overlaying the reflective layer. 

Table 2.6 Examples for Commercially Available Parylene Polymers...

Parylene polymers are not manufactured and sold directly. They are deposited from the vapor phase by a process which in some respects resembles vacuum metalizing. Parylene polymers are formed at a pressure of about 0.1 torr from a reactive dimmer in the gaseous or vapor state. Unlike vacuum metalizing, the deposition is not line of sight, and all sides of an object to be encapsulated are uniformly impinged by the gaseous monomer. Due to the uniqueness of the vapor phase deposition, Parylene polymers can be formed as structurally continuous films from as thin as a fraction of a micrometer to as thick as several mils. 

Gorham, W. F. Parylene Polymers. In Modem Plastics Encyclopedia, pp. 230-34. New York McGraw-Hill, 1969. 

In addition, the Parylene polymer series also include Parylene HT, the newest commercially available variant of Parylene. The alpha hydrogen atoms of the N dimer have been replaced with fluorine. This variant of Parylene is useful in high-temperature applications (short term up to 450°C) and those in which long-term UV stability is required. Parylene HT also has the lowest coefficient of friction and dielectric constant, and the highest penetrating ability of the four variants [153],... 

The Parylene polymers are deposited from the vapor phase by a process that in some respects resembles vacuum metallizing. Unlike vacuum metallization, however, which is conducted at pressures... 

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