Polyphenyl ether

The main synthetic fluids used as special lubricants are esters, polyglycols, silicones, halogenated hydrocarbons and polyphenyl ethers. 

Synthetic oils have been classified by ASTM into synthetic hydrocarbons, organic esters, others, and blends. Synthetic oils may contain the following compounds diaLkylben2enes, poly(a-olefins) polyisobutylene, cycloaUphatics, dibasic acid esters, polyol esters, phosphate esters, siUcate esters, polyglycols, polyphenyl ethers, siUcones, chlorofluorocarbon polymers, and perfluoroalkyl polyethers. 

Alkylated aromatic lubricants, phosphate esters, polyglycols, chlorotrifluoroethylene, siUcones, and siUcates are among other synthetics that came into production during much that same period (28,29). Polyphenyl ethers and perfluoroalkyl polyethers have followed as fluids with distinctive high temperature stabiUty. Although a range of these synthetic fluids find appHcations which employ their unique individual characteristics, total production of synthetics represent only on the order of 2% of the lubricant market. Poly(a-olefin)s, esters, polyglycols, and polybutenes represent the types of primary commercial interest. 

Polyphenyl Ethers. These very stable organic stmctures have been synthesized in a search for lubricants to meet the needs of future jet engines, nuclear power plants, high temperature hydrauHc components, and high temperature greases (49). A typical formula is C H (—OC H ... 

One hquid in this class intended for aircraft engine use is described in military specification MIL-L-87100 for operation from +15 to 300°C. Limitations of this class of synthetics are pour points of +5°C and higher, relatively poor lubricity, and high cost of 265/L ( 1000 + /gal) (44). Polyphenyl ether greases are available with good radiation resistance for appHcations in the temperature range of +5 to 288°C. 

Perfluoroalkyl ether greases thickened with polytetrafluoroethylene (MIL-G-38220 and MIL-G-27617) are used from —40 to 200°C in missiles, aircraft, and appHcations where fuel, oil, and Hquid oxygen resistance is needed (55). Polyphenyl ether greases find special use from 10 to 315°C in high vacuum diffusion pumps and for radiation resistance. 

Although synthetic lubrication oil production amounts to only about 2% of the total market, volume has been increasing rapidly (67). Growth rates of the order of 20% per year for poly( a-olefin)s, 10% for polybutenes, and 8% for esters (28) reflect increasing automotive use and these increases would accelerate if synthetics were adopted for factory fill of engines by automotive manufacturers. The estimated production of poly( a-olefin)s for lubricants appears to be approximately 100,000 m /yr, esters 75,000, poly(alkylene glycol)s 42,000, polybutenes 38,000, phosphates 20,000, and dialkyl benzene 18,000 (28,67). The higher costs reflected in Table 18 (18,28) have restricted the volume of siUcones, chlorotrifluoroethylene, perfluoroalkylpolyethers, and polyphenyl ethers. 

The membranes used are typically composed of cross-linked silicones and are suitable for on-line monitoring of volatile organic and inorganic compounds [93-94]. An alternative material is microporous PTFE, which has more rapid responses as well as lower selectivities and higher fluxes of the mobile phase compared to nonporous silicone membranes. More recently, developments in membrane introduction systems include the use of liquid membranes composed, for example, of a polyphenyl ether diffusion pump fluid [95-96]. This membrane has the advantage that it can take any desirable analyte and the selectivity can be modified using appropriate reagents. 

The immune biosensor analysis was carried out in the SPR-4 M device produced by the Institute of Physics of Semiconductors of the Ukrainian National Academy of Sciences. SPR spectroscopy was carried out in the Kretschmann configuration using He-Ne laser ( i=632.8 nm), goniometer (G-5 M), glass prism (the angle at the basis 68°) and photodiode (FD 263). The optical contact between the prism and the metallic layer was achieved by the application of polyphenyl ether (refractive index n= 1.62). 

One of the most interesting uses of emission spectroscopy is the study of the action of lubricants 162,166,167 168,169,170). A loaded steel ball is rotated in a fluid bath and made to slide over a diamond window. A contact region is formed which can be measured by the radiant power emitted. A substraction of the ball surface radiation from the total radiation emitted from the contact region was electronically carried out. A study of the emission spectra of a polyphenyl ether and a naphthenic fluid under dynamic conditions was made. The widths of some of the bands of the ether increased dramatically when a certain load (pressure) was exceeded. These increases were correlated with the changes of chemical composition through decomposition of the fluid 170,171). 

Columns prepared with polymeric stationary phases such as Carbowax, polyesters, or polyphenyl ethers, should be conditioned at a temperature at which the column will be used. These stationary phases contain polymers of varying molecular weight and the conditioning helps to remove the more volatile portions. 

Polypheny I Ethers. Both alkyl-substituted and iinsubxtiinlcd polypheny ethers are included in this class of synthetic lubricants. General preparation involves the (.llhiian ether synthesis. The unsubstituted polyphenyl ethers have outstanding thermal, oxidative and radiation resistance, however, poor low-temperature characteristics arc a major drawback. Alkyl substitution improves low-temperature viscosity, but detracts from stability. Most lubricant uses are developmental in nature and involve aircrali and aerospace applications. 

Maroulis and Bandy ( ) determined DMS in air at Wallops Island by cryotrapping air drawn through a teflon tube packed with glass beads immersed in liquid argon. The DMS was thermally desorbed onto a GC column with polyphenyl ether/H PC liquid phase coated onto a teflon substrate and was detected via doped "FPD. No mention was made in that paper of sampling losses, however it has been suggested that the presence of the glass beads may have served to remove co-trapped oxidants (D. Thornton, personal communication). 

Amines Boranes Penwalt 213 Chromosorb 103 (see support modifiers) Apiezon L beeswax carbowax 400, 1540, 4000, 20M castorwax diethylene glycol succinate di-n-decyl phthalate diisodecyl phthalate Emulphor-ON-870 ethylene glycol adipate FFAP, polyphenyl ether (5 or 5 ring) quadrol reoplex 400 SE-30 XE-60 sucrose acetate isobutyrate tricresyl phosphate Ucon series... 

Others Phosphate esters Silicone oils Halogenated fluids Polyphenyl ethers Fire resistant hydraulic fluids, gas turbine oils High temperature hydraulic fluids, brake fluids, compressor oils Extremely fire-resistant hydraulic oils Radiation-resistant, heat transfer fluids... 

Polyphenyl ether (Santovac 5) (< IO 9) Thermally stable, good oxidation resistance. Forms conducting polymers under energetic particle bombardment. Good for mass spec, and ultra-high vacuum. Not very chemically resistant. Relatively high cost. 

The fluids used in oil diffusion pumps are usually hydrocarbon esters (e.g., Ai n octylphthalate) that are heated to 130 to 160°C in operation or silicone or polyphenyl ether fluids that operate at higher temperatures (180 to 280°C). The latter fluids are quite expensive but give lower ultimate vacuum levels (10 to 10 ° Torr) and greater resistance to oxidation by excessive amounts of air. Further information is given in Table 1. Warning When hot, a diffusion pump should never be exposed to pressures above about 0.1 Torr never vent an oil diffusion pump to air when it is hot. 

Q7 y r Figure 4.30 Plot of — N l versus shear stress a for polyphenyl ether... 

Chromatography of radiochemically homogeneous terpenoids has been reviewed useful gas-chromatographic techniques reported include the use of polyphenyl ether in g.c.-m.s. of 23 monoterpenoid hydrocarbons,the use of 3,4,5-trimethoxybenzylhydrazine for pre-column removal of aldehydes and ketones, and the resolution of some bicyclic alcohols and ketones by co-injection with a volatile chiral resolving agent. 

Two years later (1989), the same authors reported the oxygenation and oxidation chemistry of the Mn-substituted POMs XMnnWn039"- (X = P, Si, Ge, or B) and a2-P2MnnWi706i8-.316 These POMs undergo reversible oxygenation at low temperature in toluene or benzene solution but irreversible oxidation above 22°C. The 02 adduct can be intercepted by the spin trap 5,5-dimethyl-1-pyrroline A-oxide (DMPO). EPR spectra indicate formation of a polyanion-02-DMP0 intermediate that decomposes to the oxidized POM. The nonpolar organic solutions of these POMs catalyze the oxidation of 2,6- and 2,4,6-substituted phenols to benzoquinones or polyphenyl ethers, and a POM-02-phenoxy radical intermediate can be detected by EPR. 

Earlier dielectric studies under elevated pressure [20,105-110] had found temperature-pressure superpositioning at constant xa in a few molecular glass-formers including ortho-terphenyl (OTP), di(2-ethylhexyl) phthalate, tricresyl phosphate, polyphenyl ether, and refined naphthenic mineral oil, although the temperature and pressure ranges are not as wide as achieved in more recent measurements. 

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