Abstract
Synthetic esters have extensively been studied and utilizeel as the jet engine oils. The earliest practical use of the synthetic esters was the diester type such as DOS. The diesters have excellent physical properties, but some are not very stable for heat. A particular type in which β-carbon of alcohol moiety is quarternary, is called a “hindered ester”, which shows an improved thermal stability over those having non-quarternary β-carbon, Polyols such as trimethylolpropane, pentaerythritol etc., give the type of esters with carboxylic acids. The thermal stability is further improved by employing an acid having a quarternary α-carbon; the resultant ester is often referred to as a “neoacid ester”. The neoacid ester, however, exhibits not better pbysical properties than the diesters and hindered esterss especially on the viscosity-temperature characteristics, low temperature fluidity and volatility. There are some other esters; fluorinated esters, oxidatively autoinhivitive esters, etc.
