Phospha-s-Triazines and Other Compounds for Use as Additives

A report describes research on selected compounds as additives to perfluoroalkyether (PFPAE) fluids that are used as synthetic lubricants for metal parts. Additives are needed to inhibit both thermo-oxidative degradation of, and corrosion of metals by, the PFPAE fluids in the presence of oxidizing atmospheres. [An earlier phase of this research was reported in "Performance of Perfluoroalkylether Lubricant System" (LEW-15603), NASA Tech Briefs, Vol. 19, No. 9 (September 1995), page 123.] The phase of research described in the present report included (1) synthesis of novel phospha-s-triazines, phosphate esters, and related additive compounds and (2) evaluation of these and previously available additives with respect to degradation- and corrosion-inhibiting behavior and thermal and hydrolytic stability, in an effort to develop a data base of optimum PFPAE/additive/alloy combinations. The other materials included in the study were six different alloys and four commercial PFPAEs. None of the additives tested was found to undergo hydrolysis at a temperature of 100 °C. The phosphate esters were found to be the most effective and, in particular, were fully effective in arresting the degradation of the PFPAEs in the presence of metal alloys and oxygen at temperatures up to 300 °C. In an overall rating, the additives in order of decreasing effectiveness were found to be phosphates > phosphate/diester mixture > phosphine > phospha-s-triazines.