Submitted to: American Oil Chemists' Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2005
Publication Date: May 4, 2005
Citation: Kurth, T.L., Biresaw, G. 2005. Cooperative adsorption behavior of methyl fatty esters from hexadecane via coefficient of friction measurements [abstract]. American Oil Chemists' Society Meeting. p. 57. Technical Abstract: The frictional behaviors of methyl oleate (MO), methyl palmitate (MP), methyl laurate (ML), and methyl stearate (MSt) as additives in hexadecane have been examined in a boundary lubrication test regime using steel contacts. Critical additive concentrations were defined and used to perform novel and simple Langmuir analyses that provide an order of adsorption energies: MSt > MP > MO greater than or equal to ML. Application of Langmuir, Temkin, and Frumkin-Fowler-Guggenheim (FFG) adsorption models via non-linear fitting demonstrates the necessary inclusion of cooperative effects in the applied model. In agreement with the qualitative features of steady-state COF-concentration plots, MSt displays minimal cooperative adsorption. MO, MP, and ML data require large attractive interaction terms (beta greater than or equal to 4) to be adequately fit. Primary adsorption energies calculated via the cooperative model are necessarily decreased while total adsorption energies correlate well with values obtained via critical concentration analyses. These results and comparisons with previous adsorption studies of MO and MSt suggest that secondary alkyl-surface-, adsorbent-adsorbent-, and adsorpt-adsorpt-interactions cumulatively determine the calculated adsorption and cooperative interaction energies.