Sorption of Lubricant Additives by Porous Plastic Retainer Materials

Sorption of additives present in lubricating oils by porous plastic retainer materials was studied by liquid chromatographic experiments. Liquid chromatography columns were packed with finely shredded porous cotton-phenolic and polyimide ball bearing retainer materials. Small aliquots of nonpolar hydrocarbon oils (purified by molecular distillation and prepared to contain additives of various polarities) were individually eluted through, the columns with n-hexane. The eluate from each of the columns was evaporated, and the residues were analyzed for additive content. Atomic absorption and computer-controlled electron-impact mass spectrometry of the eluted samples provided evidence of retention of the lubricant additives in the column. The degree of depletion of additives from the oil samples appears to be a function of the polarities of both the retainer matrix and the additive molecules, and the hydrogen bonding or dipole-dipole interaction resulting therefrom.