A study of the effect of chemical structure on friction and wear: Part I -Synthetic ester base fluids

The proper formulation of lubricants starts with an understanding of the pe rformance of the individual base stocks. Additives respond to various base stocks differently depending on the chemistry of the base stock and can res ult in either synergistic or antagonistic effects. This paper studies the e ffect of structure for various ester base stocks using a four-ball wear tes t machine to measure friction and wear. The authors evaluate several esters based on differing chemical structures of the alcohol and acid moieties us ed to synthesize the ester. The alcohols include neopentyl glycol (NPG), tr imethylolpropane (TMP), and pentaerythritol (PE). Acids vary in length of t he molecular chain and comparisons include both branched and linear molecul es. The researchers blend various additives in the base stocks to study the interaction with the base fluids. Wear tests occur in the boundary lubrica tion regime with significant chemical structure differences observed.