Aromatic phosphate esters such as triphenyl phosphate, tricresyl phosphate (TCP), and
tri(tert-butylphenyl) phosphate, have been degraded in the presence of pure iron or metal
alloys such as M-50 or 52100 steel. Among these volatile degradation products are those
generated from the addition of an aromatic ring to the phosphate ester. Other products,
which have been identified, include substituted biphenyls and diphenyl ethers derived from
the decomposition of the above-mentioned addition product. Still other products are fused
ring aromatic compounds such as anthracene, which arise from secondary reactions of the
initial decomposition reactions. The decomposition reactions leave a nonvolatile phosphate
film on the surface of the metal. Characterization of the film with Auger spectroscopy suggests
iron phosphate as the product. X-ray photoelectron spectroscopy shows the presence of a
bound organic layer at the surface. A mechanism that explains many of the decomposition
products and the formation of a bound glassy iron phosphate film is proposed.
Chromatographic and spectroscopic techniques were used to investigate the degradation products from bulk oxidative and thermal stability testing of a substituted tricyclophosphazene high-temperature lubricant. Analytical investigation into the degraded lubricant revealed oligomerization to be the dominant mode of degradation, resulting in most of the observed viscosity increases. GC/MS, FT-IR, and (31)P NMR data confirmed the existence of a cyclotetramer structure in the degraded fluid, while GPC analysis indicated the possibility of a much smaller amount of higher oligomers. The poor reproducibility observed for the oxidation results is likely due to the influence of trace contaminants or the relative degree of retention of ionizable volatile products that could act as oligomerization catalysts.
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