Hydrolysis of phosphate‐based aviation hydraulic fluids

Abstract

High‐temperature in‐service failure of phosphate ester‐based aviation fluids is primarily due to acid‐catalysed hydrolysis. The reaction is controlled with epoxides, but careful attention to the other additives is needed to avoid including species which catalyse hydrolysis. From an airline's point of view, water concentration is the critical factor, since it is the only variable that it can control. From a system designer's point of view, minimising fluid temperature should be a goal. Plots relating fluid life to temperature and water level for typical commercial fluids are included.

Chemical pathways of epoxidized and hydroxylated fatty acid methyl esters and triglycerides with phosphoric acid

“…The formation of 2-hydroxyphosphates from epoxides and phosphoric acid consistent with pathway a is well documented. [13][14][15] Furthermore, ample precedence has been provided for the establishment of ether networks from the acid-catalyzed reaction of epoxides with nucleophilic alcohols via an activated monomer mechanism (AM) 11,16 consistent with pathway b. 17,18 If pathway b contributes to the overall polymeric network at least in part, calculated addition of polyols to the reaction mixture would amplify initiation events during polymerization.…”