Polyphenyl ether
Low molecular weight polyphenyl ethers and thioethers are used in a variety of applications, and include high-vacuum devices, optics, electronics, and in high-temperature and radiation-resistant fluids and greases.
[3] Physical properties of a particular PPE depend upon the number of aromatic rings, their substitution pattern, and whether it is an ether or a thioether.
The melting points of the ordinarily solid PPEs are lowered if they contain more m-phenylene rings, alkyl groups, or are mixtures of isomers.
[4] Oxidation stability of un-substituted PPEs is quite good, partly because they lack easily oxidizable carbon-hydrogen bonds.
[5] Excellent radiation stability of PPEs can be ascribed to the limited number of ionizable carbon-carbon and carbon-hydrogen bonds.
Data presented in Table 3 demonstrates polyphenyl ether to be superior to other fluids that are commonly used in diffusion pumps.
This PPE property tends to keep the film stationary, or at least to cause it to remain in the area where the lubrication is needed, rather than migrating away by spreading and forming a new surface.
Polyphenyl ether lubricants have a 30-year history of commercial service for connectors with precious and base metal contacts in telecom, automotive, aerospace, instrumentation and general-purpose applications.
[9][10] In addition to maintaining the current flow and providing long-term lubrication, PPEs offer protection to connectors against aggressive acidic and oxidative environments.
The devices that benefit from the specialized properties of PPEs include cell phones, printers, and a variety of other electronic appliances.
Because of these, PPEs have the ability to meet the rigorous performance demands of signal processing in advanced photonics systems.
Close refractive index (RI) matching between materials is important for proper propagation of light through them.
Extreme resistance to ionizing radiation gives PPEs an added advantage in the manufacture of solar cells and solid-state UV/blue emitters and telecommunication equipment made from high-index glasses and semiconductors.
While the use of PPEs in lubricating jet engines has somewhat subsided due to their higher cost, they are still used in some aerospace applications.
PPEs and their derivatives have also found use as vapor phase lubricants in gas turbines and custom bearings, and wherever extreme environmental conditions exist.
Polyphenyl ether technology can also provide superior fire safety and fatigue life, depending on the specific bearing design.
Due to the low volatility and excellent high-temperature thermo-oxidative stability, PPEs have also found use as a lubricant for chains used in and around kilns, metal fabrication plants, and glass molding and manufacturing equipment.
[11] These polymers are made through oxidative coupling of substituted phenol in the presence of oxygen and copper and amine containing catalysts, such as cuprous bromide and pyridine.
They and their composites with polystyrene, glass, and nylon are used as high-strength, moisture-resistant engineering plastics in a number of industries, including computer, telecommunication, and automotive parts.
