High Temperature Decomposition of Military Specification L-23699 Synthetic Aircraft Lubricants

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Abstract
Previous investigations reported the formation of a neurotoxicant, tri methylolpropane phosphate (TMP-P) during pyrolysis of synthetic, aircraft engine lubricating oils. Employing both sealed-tube and open-to-air methods of pyrolysis, we confirmed the formation of TMP-P during lubricant pyrolysis. Rodent bioassay and GC/MS analysis were performed for detection and quanti tation of neurotoxicant production. Maximal production of TMP-P for sealed- tube pyrolysis occured after 20 min at 500°C. A comparable amount of TMP-P was formed after 5 min at 650°C in open-to-air pyrolysis of lubricants. Our examination of TMP-P production was limited to L-23699 lubricants composed primarily of a trimethylolpropane (TMP) ester base stock. The formation of TMP-P was only dependent upon the presence of an organic phosphorous addi tive and TMP. Pyrolysed lubricants composed of a pentaerythritol base did not cause neurotoxicity in mice or rats following intraperitoneal (i.p.) injection. Other toxic bicyclophosphorous ester homologues were not detected in any pyrolyzed lubricants following GC/MS analysis. L-23699 lubricants which had been operationally employed in aircraft engines under rigorous test conditions, produced no neurotoxicity when intraperitoneally administered to rats.

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