Parylene

Parylene is the tradename for a variety of polyxylylene polymers marketed by several providers, including Kisco Conformal Coating, LLC [cite web | url = http://http://www.uniglobe-kisco.com/dix_introduction.htm | title = Introduction to Parylene | publisher = Uniglobe Kisco, Inc. | accessdate = 2008-04-28] , Para Tech Coating, Inc. [cite web | url = http://www.parylene.com/technology/parylene-technology.html | title = Parylene Technology | publisher = Para Tech Coating, Inc. | accessdate = 2007-07-07] , Specialty Coating Systems, Inc. [cite web | url = http://www.scscoatings.com/parylene_knowledge/history.aspx| title = Parylene Knowledge| publisher = Specialty Coating Systems, Inc. | accessdate = 2007-11-25] , and others. Parylene N is a polymer manufactured from di-p-xylylene, a dimer synthesized from "p"-xylylene. Di-p-xylylene, more properly known as [cyclophane| [2.2] paracyclophane] , is made from p-xylylene in several steps involving bromination, amination and elimination. [OrgSynth | collvolume = 5 | collvolumepages = 883 | year = 1973 | prep = cv5p0883 | title = Tricyclo [8.2.2.24,7] hexadeca-4,6,10,12,13,15-hexaene | author = H. E. Winberg and F. S. Fawcett]

There are a number of derivatives and isomers of parylene, but only a few are used commercially, e.g., Parylene N, Parylene C and Parylene D. This article discusses the unsubstituted molecule, which produces Parylene N. Heating [2.2] paracyclophane in a partial vacuum gives rise to a diradical species [cite journal
title = Macro rings. XXXVI. Ring expansion, racemization, and isomer interconversions in the [2.2] paracyclophane system through a diradical intermediate
author = H. J. Reich, D. J. Cram
journal = Journal of the American Chemical SocietyEdition
volume = 91
issue = 13
pages = 3517–3526
year = 1969
doi = 10.1021/ja01041a016] [*cite journal
title = Polymerization of para-xylylene derivatives (parylene polymerization). I. Deposition kinetics for parylene N and parylene C
author = P. Kramer, A. K. Sharma, E. E. Hennecke, H. Yasuda
journal = Journal of Polymer Science: Polymer Chemistry Edition
volume = 22
issue = 2
pages = 475–491
year = 2003
url =
doi = 10.1002/pol.1984.170220218] which polymerizes when deposited on a surface. Until the "monomer" comes into contact with a surface it is in a gaseous phase and can access the entire exposed surface. It has a variety of uses. In electronics, chemical vapor deposition at low pressure onto circuit boards produces a thin, even conformal polymer coating. Parylene coating has very high electrical resistivity and resists moisture penetration. It is used as a dielectric in certain high-performance capacitors for precision measurement. It has uses in preserving archival paper.

Characteristics and advantages

* Hydrophobic, chemically resistant coating with good barrier for inorganic and organic media, strong acids, caustic solutions, gases and water vapour.
* Outstanding electrical isolation with high tension strain and low dielectric constant
* A biostable, biocompatible coating, FDA permission
* micropore and pin get-free starting from 0.2 µm layer thickness,
* Thin and transparent coating with high gap freedom of movement, suitably for complex arranged substrates also on edges.
* Coating without temperature load of the substrates, coating takes place at ambient temperature in the vacuum.
* Highly corrosion resistant.
* Completely homogeneous surface.
* Thermally stable up to 220 °C, mechanically stable from -200 °C to +150 °C.
* Low mechanical stresses.
* Resistant to friction.
* Very low permeability to gases.
* High electrical impedance.

Typical applications

* Dielectric coating (e.g. Cores/coils).
* Hydrophobic coating (e.g. biomedical hoses).
* Barrier layers (e.g. for filter, diaphragms, valves).
* Microwave electronics.
* Sensors in rough environment.
* Electronics for space travel and military.
* Corrosion protection for metallic surfaces.
* Reinforcement of micro-structures.
* Abrasion protection.
* Protection of plastic, rubber, etc. from harmful environmental conditions.
* Reduction of friction (e.g. For guiding catheters, also acupuncture needles).
* Dissolving deuterated polyethylene for making nuclear targets.

External links

* [http://www.uniglobe-kisco.com/dix_introduction.htm Introduction to Parylene]
* [http://www.scscoatings.com/parylene_knowledge/history.aspx Parylene History]
* [http://www.parylene.com/technology/specifications-properties.html Parylene Specifications and Properties]
* [http://www.vp-scientific.com/parylene_properties.htm Parylene Properties & Characteristics]

References