Engineering topics

Nakahara, James H.

Publications and source records attributed to Nakahara, James H..

3 records

NASA NTRS1996

Evaluation of Degradation Inhibitors in Poly(Hexafluoropropene Oxide) Fluids

The action of various alloys: 440C steel, M-50 steel, Pyrowear 675, Cronidur 30 and Ti(4Al,4Mn); the effect of decradation inhibitors: mono- and diphospha-s-triazines, diphosphatetraazacyclooctatetraene, phosphate esters, phosphate/ diester rust inhibiting mixtures, and a phosphine were evaluated in two poly(hexafluoropropene oxide) fluids (143AC and 16256). The degradation promoting action of the ferrous alloys in 16256 fluid were comparable; Ti(4Al,4Mn) alloy was significantly more detrimental. The overall rating of the additives was: phosphates (greater than) phosphate/diester mixture (greater than) phosphine (greater than or equal to) phospha-s-triazines. The 16256 fluid was less responsive to additive inhibition than 143AC. Phosphate esters were fully effective over 24 hour exposure in the 16256/440C steel and the 16256/Ti(4Al,4Mn) systems at 330 C. In general, the phosphine was less effective in the presence of ferrous alloys than the phosphates and phospha-s-triazines.

Jones, William R., Jr.↗

NASA NTRS1987

Improved perfluoroalkyl ether fluid development

The feasibility of transforming a commercial linear perfluoroalkylether fluid into a material stable in the presence of metals and metal alloys in oxidizing atmospheres at 300 C without the loss of the desirable viscosity temperature characteristics was determined. The approach consisted of thermal oxidative treatment in the presence of catalyst to remove weak links, followed by transformation of the created functional groups into phospha-s-triazine linkages. It is found that the experimental material obtained in 66 percent yield from the commercial fluid exhibits, over an 8 hr period at 300 C in the presence of Ti(4Al, 4Mn) alloy, thermal oxidative stability better by a factor of 2.6 x 1000 based on volatiles evolved than the commercial product. The viscosity and molecular weight of the developed fluid are unchanged and are essentially identical with the commercial material. No metal corrosion occurs with the experimental fluid at 300 C.

Jones, William R., Jr.↗

NASA NTRS1977

Mass Spectra of Some Perfluoroalkyl and Perfluoroalkylether Substituted 1,2,4-Oxadiazoles

Electron impact fragmentation patterns were obtained for 1,4-bis[(5-perfluoro-n-heptyl)-1,2,4-oxadiazolyl- benzene, its perfluoroalkylether substituted analogue, 3,5-bis(perfluoroalkyl)-, 3,5-bis(perfluoroalkylether)- and 3-perfluoroalkylether-5-perfluoroalkyl-1,2,4-oxadiazoles. In the compounds containing the phenylene group the molecular ion constituted the base peak; the main process was the breakdown of the oxadiazole ring with concurrent liberation of the perfluoroalkyl or perfluoroalkylether nitrile molecule; cleavage of the fluorinated chain ot to the oxadiazole ring was found to take place to a considerable degree. In the perfluorinated 1,2,4-oxadiazoles cleavage beta to the oxadiazole ring occurred preferentially; fragmentation of the ring itself took place to a limited degree only. The 3-perfluoroalkylether-5-perfluoroalkyl-1,2,4-oxadiazole appeared to undergo the primary beta-cleavage exclusively at the perfluoroalkylether sidechain.

Paciorek, Kazimiera J. L.↗