Machine Design

A short history of parylene

In 1947, Michael Szwarc was pursuing his academic career in physical chemistry at the Univ. of Manchester, England. His interest in the strength of individual chemical bonds led him to investigate a class of aliphatic carbon-hydrogen bonds in which the carbon was directly attached to a benzene ring. While doing so, he heated gases of the simplest compounds having both benzene and carbon — toluene and the xylenes — to high temperatures. He monitored both the decomposition products and rates of decomposition as a function of temperature.

With p-xylene only, a tan-colored deposit formed in the cooler reaches of his glassware. The material has been described as a thin, € imsy, tube-shaped mass, “the skin of a small snake.”

Szwarc correctly deduced that this … lm had been formed by polymerizing reaction products of the p-xylene, called p-xylylene. He also noticed the new polymer’s physical properties and chemical inertness. This serendipitous polymerization was the world’s … rst vapor deposited poly(paraxylyene). Today its purer colorless form is called parylene N.

A few years later, William Franklin Gorham at Union Carbide Corp. continued the research on parylene. By 1967, this work led to the availability of a new polymeric coating. “Parylenes” was the term used to describe both a new family of polymers and the vacuum-deposition process for applying them. In fact, Union Carbide developed over 20 types of parylene, but only three were deemed commercially viable.

© 2012 Penton Media, Inc.

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