Ester basestock vaporisation from thin oil films

Abstract

AbstractVolatile materials, released by lubricants, relate to various engineering, occupational and workmanship aspects. Most tests (flash point, NOACK, TGA etc.) assess thermodynamic evaporation without focusing on prolonged oxidation and hydrolysis, which can also produce volatiles, especially in unsaturated esters. A thin film test was adapted for long‐term (2000 h+) vaporisation studies in dry or humid atmosphere. Rapeseed oil and oleate esters showed initial weight gain due to peroxide formation at 50–130°C. Only afterwards release of volatiles began and approached 5%wt. in rapeseed oil. FTIR demonstrated significant oxidation even in cetane. Antioxidants had only slight effects on rates and tendencies, while 20% relative humidity clearly accelerated vaporisation. Acidity buildup was much faster in oleyl alcohol than in stearyl alcohol despite similar vaporisation trends. Although decomposition appeared much slower than the combined rate of oxypolymerisation and saponification, such film‐based methodology represents a powerful tool to investigate long‐term vaporisation tendencies of lubricants. © 2017 John Wiley & Sons, Ltd.