Di-para-xylylene

The parylene coating process is a three-step procedure that includes vaporization, pyrolysis, and polymerization. The parylene C coating process, shown schematically in Fig. 15.8, begins with the vaporization of the precursor dimer (di-para-xylylene), a granular white powder, at 150 °C and a pressure of 1 Torr. This... 

The schematic of the para-xylylene monomer polymerization [5] is presented in Fig. 2. The monomer beam was introduced from the source consisting of the zone of evaporation of di-para-xylylene and its pyrolysis zone. Di-para-xylylene was introduced into the evaporation zone, which then evaporated (without destruction) in the temperature range 350-400 K. Then the molecnles of di-para-xylylene reached the pyrolysis zone with a temperature of 930 K. Under these conditions the C-C bond shows destruction with almost 100% output of bi-radical. The monomer thus obtained condenses onto the cooled substfate. With heating up to room temperature, the condensed monomer polymerises into PPX as indicated in Fig. 2. 

Another novel membrane formation process to yield thin film coatings involves the polymerization of di-para-xylylene onto the desired substrates. This process involves subjecting di-para-xylylene (or a substituted version) to high temperature in a high-vacuum chamber. The di-para-xylylene forms a di-radical that polymerizes and uniformly coats all surfaces in the vacuum chamber. This produa/process termed Parylene has been employed commercially for over four decades to provide protective coatings for electronic devices and medical devices as well as more recendy for micropatterned surfaces in biomedical implants and biosensors. ... 

Paralene [para-xylene] Also called Gorham and also spelled parylene. A process for coating articles with poly-p-xylene. The vapor of di-p-xylylene is pyrolyzed at 550°C, yielding p-xylyl free radicals, -CHj-CgH CH, which deposit and polymerize on cooled surfaces. Developed by W. F. Gorham at Union Carbide Corporation. 

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