CHARACTERIZATION OF ENGINE MOTOR OILS DISPERSANTS OF THE POLYBUTENYLSUCCINIMIDE TYPE BY SAPONIFICATION, METHYLATION AND SIZE-EXCLUSION CHROMATOGRAPHY

Characterization of the molecular weight distribution (MWD) of the sta rting polybutene (PBU) used in the synthesis of dispersants of the pol ybutenylsuccinimide type used in lubricants can be achieved through si ze exclusion chromatography after a preliminary chemical treatment con sisting of saponification followed by acidification and methylation wi th diazomethane. This treatment can be checked by Fourier transform in frared spectrometry since each compound - the original dispersant, the PBU succinic acid derivative and the corresponding methyl ester - has typical absorption bands. The method was tested with model dispersant s synthesized from known starting PBUs and applied to dispersants cont ained in commercial engine motor oils.