Parylene

Parylene is the tradename for a variety of polyxylylene polymers marketed by Para Tech Coating, Inc. Parylene C is a polymer manufactured from di-p-xylene, a dimer of p-xylene. Di-p-xylene, more properly known as [2.2]paracyclophane, is made from p-xylene in several steps involving bromination, amination and elimination.

There are a number of derivatives and isomers of parylene, but only a few are used commercially. This article discusses the unsubstituted molecule, which produces Parylene C. Heating [2.2]paracyclophane in a partial vacuum gives rise to a diradical species 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 stably of -200 °C to +150 °C.
 * Low mechanical stresses.
 * Resistant to friction.
 * Does not allow gas to pass through.
 * 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.).
 * Dissolving deuterated polyethylene for making nuclear targets.