Materials Compatibility

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Ultraviolet Resistance[edit]

from UV Properties of Plastics: Transmission & Resistance

Good resistance to ultraviolet rays can be achieved from polymers extruded by Zeus such as PTFE, PVDF, FEP, and PEEKTM. The only plastics found with excellent resistance are the imides, Polyimide (PI) as used in the Hubble Space Telescope and Polyetherimide (PEI).

PTFE has particularly good UV resistance because of its very strong carbon-fluorine (C-F) bond—almost 30% higher than the carbon-hydrogen (C-H) bond]—which is the common side bond that surrounds the carbon (C-C) backbone in a helix and protects it. Most fluoropolymers also do not have the light absorbing chromophore impurities in their structure that can act as an initiator for photo-oxidation.

Common Incompatibilities[edit]

Oxygen[edit]

Causes oxidative damage to many organic materials and elastomers; may react with metals to form a thin ‘passivation layer’ of the metal oxide that protects the base metal underneath. Incompatible with aluminum, Buna-N (nitrile rubber), and Neoprene. Viton A or similar fluoropolymer should be used in O-rings that contact elevated oxygen concentrations.

Hydrogen[edit]

Hydrogen is a very small molecule, and it is therefore very soluble in many metals, causing them to embrittle and crack. Hydrogen embrittlement is primarily a concern in high-strength alloys of nickel, titanium, and steel, which have microscopic imperfections in their crystal structures that act as recombination points for dissolved hydrogen atoms. Steel exposed to high-temperature hydrogen may internally generate methane in a process known as ‘hydrogen attack’. Hydrogen may be somewhat incompatible with natural rubber and silicone.

Carbon Dioxide[edit]

Carbon dioxide causes rapid failure of cast iron, and has a small degree of incompatibility with aluminum, brass, ABS plastic, natural rubber, neoprene, silicone, and Viton A.

Inert Gases[edit]

Nitrogen, argon, helium, neon—compatible with just about everything.

References[edit]