Partly Fluorinated Lubricating Oils and Greases for as LOX-Compatible Lubricants

Abstract

Glutarate, camphorate, tricarballylate, phosphate, phosphonate, ether phosphonitdate, and cyanurate derivatives of partly fluorinated alcohols, H(CF2) .CH20H, were prepared, characterized, and screened for stability under impact in the presence of liquid oxygen. All substances examined exhibited a high degree of stability. The results allowed some correlation between the stability of the sub'stances and the degree and type of hydrogen substitution in the materials. Pour points and normal boiling points for all the liquids are reported, with additional data on volatility, corrosiveness, a n d viscosity of the glutarates. The glutarate oils were thickened with fluorocarbon telomer and the aluminum shear reactivities of the resulting greases were determined. No reactions were observed.THE need for lubricating greases compatible with liquid oxygen (LOX) for lubrication requirements in rocket motors and descriptions of availatle materials have been discussed by Fisch et a/. (1962), Messina and Gisser (1963), Messina (1967), and Delatt et al. (1967. Substances found most compatible with liquid oxygen are perfluorinated materials, particular1:y the perfluoroalkylamines and perfluoroalkyl ethers. Perfluorinated organic substances usually exhibit smaller liquid ranges than the corresponding hydrocarbyl compounds, and have a low activation energy for viscous flow. As a consequence, many of these substances may have high pour points, high vapor pressures at elevated temperature, and poor viscositytemperature relationships.Although LOX-compatibility data are available for some perfluorinated materials, very few data are available for partly fluorinated materials that will allow a correlation of chemical structure with stability. I t is probable that the degree of compatibility will be related to the extent of fluorination (the ratio of fluorine to hydrogen), the sequence of hydrogen and fluorine in the chemical structure, and the presence of other groups or atoms, such as silicon, phosphorus, or oxygen, in the lubricant structure. Each of these modifications can also affect the liquid range properties of a substance. Messina (1967) and Gumprecht (1966) have shown that the incorporation of ether-oxygen into a perfluorinated structure very substantially improves the temperature-vapor pressure rela-