Submitted to: Tribology Letter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2009
Publication Date: 8/11/2009
Citation: Asadauskas, S.J., Biresaw, G., McClure, T.G. 2009. Effects of Chlorinated Paraffin and ZDDP Concentrations on Boundary Lubrication Properties of Mineral and Soybean Oils. Tribology Letters. 37(2):111-121. Interpretive Summary: This research demonstrated that substitution of petroleum-based oils by soybean or other seed oils in biobased lubricant formulations can provide substantial cost benefits without sacrificing performance. Development of farm-based raw materials for lubrication and other uses is aggressively being pursued because of the numerous potential benefits to the environment, safety and health of citizens, reduced reliance on imported petroleum, and strengthened rural economy. Successful substitution of petroleum-based fluids by biobased fluids requires that the later is competitive both in cost and performance. In this work it was discovered that the biobased formulations performed as well as or better than petroleum-based formulations with just one-fourth the amount of critical formulation ingredients. Since these ingredients are the most expensive components of the lubricant formulations, their concentration has a big impact on the price of the lubricant. This means that biobased lubricants can be formulated to be competitive with petroleum-based lubricants both in performance and cost.
Technical Abstract: The effect of chlorinated paraffin (CP) and zinc di-ethylhexyl dithio phosphate (ZDDP) concentration in polar and non-polar base fluids on boundary lubrication properties was investigated. The non-polar fluid was a solvent refined low sulfur heavy paraffinic mineral oil (150N oil); and the polar fluid was conventional alkali-refined food grade soybean oil (soy oil). The concentration of EP additives in the base stocks were varied 0-20% (w/w). Two different methods were used to evaluate boundary lubrication properties: ASTM D2783 four-ball extreme pressure (4-ball EP) and twist compression testing (TCT). Experimental outputs were weld point, (kgf) for 4-ball EP and time-to-failure (TTF) or Coefficient of Friction (COF) for TCT runs at 200 MPa or 8 MPa contact pressures, respectively. All tests showed that blends of 150N oil needed more than 20% EP additive treat levels to achieve similar boundary lubrication performance as blends of soy oil containing 5% of the corresponding EP additives. Also, incorporation of 20% soy oil into 150N oil-based blends resulted in the improvement of the performance to nearly the same level as the corresponding neat soy oil-based blends. The boundary lubrication properties of some of the soy oil containing blends were also found to be similar to those of a commercial straight oil chlorinated metal forming lubricant. The influence of base stock on EP additive response was very pronounced. The findings of this work suggest that soybean oil and probably other farm-based polar base fluids may provide strategies for formulating cost effective industrial fluids, gear lubricants and possibly engine oils.