Surface tension studies of alkyl esters and epoxidized alkyl esters relevant to oleochemically based fuel additives

There are several reports on the synthesis of fuel additives based on oleochemical esters, and physical data on some of these compounds is lacking. Herein, we report the surface tension of several epoxidized oleochemicals and their comparable fatty esters, at temperatures between 25 and 60 degrees C. Surface tensions of the olefins measured at 40 degrees C range from 25.9 mN m(-1), for isobutyl oleate, to 28.4 mN m(-1) for methyl linoleate. The epoxy versions of the same compounds displayed higher surface tensions of 28.1 and 32.1 mN m(-1), respectively. Branched ester compounds also had surface tensions between 27.4 and 30.2 mN m(-1). Several trends and observations were elucidated. More epoxidation or unsaturation leads to higher surface tension. Epoxidation has a larger effect on surface tension than unsaturation. Linear alkyl headgroups on fatty esters have similar surface tensions, but branched headgroups gave slightly lower surface tensions. Soy methyl esters, or epoxy soy methyl esters, give surface tensions which are between that of their two main components. Overall, the results show that all of these compounds have surface tensions which make them suitable for use as biofuel additives.