Engineering Commons^™

Tribological Characteristics Of Perfluoropolyether Liquid Lubricants Under Sliding Conditions In High Vacuum, Masabumi Masuko, William R. Jones Jr, Larry S. Helmick

Science and Mathematics Faculty Publications

Tribological characteristics of three PFPE's (Fomblin Z, Demnum, and Krytox) were studied under high vacuum using a four-ball apparatus with 440C steel specimens. Fomblin Z and Demnum exhibited initial scuffing-like high friction whereas Krytox did not. Steady state friction with Fomblin Z was the lowest among the three oils. Frictional values for Demnum and Krytox were almost the same. The lowest wear rate in air was provided by Krytox regardless of load, and low wear rates in vacuum at high load were achieved with Krytox and Demnum. Results are explained by reactivity and pressure-viscosity characteristics of the oils.

Determination Of The Oxidative Stability Of Perfluoropolyalkyl Ethers And Correlation With Chemical Structure, Larry S. Helmick, William R. Jones Jr

Science and Mathematics Faculty Publications

The oxidative stabilities of several perfluoropolyalkyl ethers (PFPAE) with related chemical structures were determined by thermal gravimetric analysis and correlated with their chemical structures. These results show that oxidative stability increases as the number of difluoroformal groups decreases and as trifluoromethyl substituents are added. They are also consistent with a recently proposed intramolecular disproportionation reaction mechanism involving coordination of successive ether oxygens to a Lewis acid. Since polytetrafluoroethylene contains no oxygen, it provides an indication of the upper limit to oxidative stability of PFPAE fluids. These results also show that oxidative decomposition of PFPAE fluids requires the presence of an …

Determination Of The Thermal Stability Of Perfluoropolyalkyl Ethers By Tensimetry, Larry S. Helmick, William R. Jones Jr

Science and Mathematics Faculty Publications

The thermal decomposition temperatures of several perfluoropolyalkyl ether fluids were determined with a computerized tensimeter. In general, the decomposition temperatures of the commercial fluids were all similar and significantly higher than those for noncommercial fluids. Correlation of the decomposition temperatures with the molecular structures of the primary components of the commercial fluids revealed that the stability of the fluids was not affected by carbon chain length, branching, or adjacent difluoroformal groups. Instead, stability was limited by the presence of small quantities of thermally unstable material and/or chlorine-containing material arising from the use of chlorine containing solvents during synthesis. Finally, correlation …

Determination Of The Thermal Stability Of Perfluoroalkylethers, Larry S. Helmick, William R. Jones Jr

Science and Mathematics Faculty Publications

The thermal decomposition temperatures of several commercial and custom synthesized perfluoroalkylether fluids were determined with a computerized tensimeter. In general, the decomposition temperatures of the commercial fluids were all similar and significantly higher than those for custom synthesized fluids. Correlation of the decomposition temperatures with the molecular structures of the primary components of the commercial fluids revealed that the stability of the fluids is not affected by intrinsic factors such as carbon chain length, branching, or cumulated difluoroformal groups. Instead, correlation with extrinsic factors revealed that the stability may be limited by the presence of small quantities of thermally unstable …

Determination Of The Thermal Stability Of Perfluoroalkylethers By Tensimetry: Instrumentation And Procedure, Larry S. Helmick, William R. Jones

Science and Mathematics Faculty Publications

A computerized tensimeter and experimental procedure for determination of the thermal decomposition temperature (Td) of perfluoroalkylethers have been developed and tested. Both the I+ m apparatus and the procedure are described in detail. Results of QU) testing with bis(2-ethylhexyl) phthlalate and trimethylolpropane wI triheptanoate demonstrate that the reciprocal of the decomposition temperature is a linear function of the logarithm of the gas volume/heated liquid volume ratio. The Td obtained for each compound at a gas volume/heated liquid volume ratio of one was similar to the value previously reported using an isoteniscope technique. Results of testing with a polymer of hexafluoropropylene …

Ftir Analysis Of Aviation Fuel Deposits, Larry S. Helmick, Gary T. Seng

Science and Mathematics Faculty Publications

Five modes of operat1on (absorpt1on, em1ssion, single reflectance, attenuated total reflectance, and photoacoust1c) of a N1colet 7199 Fourier Transform Infrared Spectrophotometer have been 1nvest1gated in order to determ1ne which modes were most su1table for qualitative analysis of jet fuel depos1ts. The absorption and emission modes were'found to be the most advan~ tageous for invest1gation of the bulk and surface propert1es of accelerated storage/thermal depos1ts where relat1vely large quantit1es of depos1t are generally ava1lable.

The general effects of fuel type, stress temperature, stress time, type of sp1k1ng agent, sp1k1ng agent concentration, fuel flow, and postdepos1t1onal treatment on the chem1cal nature of …