L. J. Tomašek

University of Zagreb

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Zvonimir Janović

University of Zagreb

Ante Jukić

University of Zagreb

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SUNY Polytechnic Institute

University of Massachusetts Amherst

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Gaylord Hospital

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University of Arizona

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Polyolefin and poly(alkyl methacrylate) mixed additives as mineral lubricating oil rheology modifiers

Lubrication Science (2005)

Ante Jukić L. J. Tomašek Zvonimir Janović

Some rheological properties of mineral lubricating oils containing polyolefin (OCP) (ethylene/propylene copolymer) and poly(alkyl methacrylate) (PAMA) mixed additives over a wide composition range have been examined. Increasing the OCP content significantly increases the viscosity and shear stability of solutions, whereas the viscosity index is directly proportional to the PAMA content. The pour point values of the additive solutions investigated are lower than −30°C even for the smallest concentration of PAMA in the polymer mixture of 15 wt.% (at a total polymer mixture concentration in oil of 2 wt.%). The viscosities of dilute mixed additive solutions obey the typical Krigbaum-Wall equation and, due to the negative viscometric interaction parameter values (Δb12 < 0), the OCP/PAMA mixture is found to be immiscible. The immiscibility becomes more pronounced on increasing the overall polymer concentrations. The viscosities of concentrated mixed additive solutions decrease significantly with an increase of OCP content, showing a minimum of half the initial value at a polymer ratio of about 50/50. On decreasing the polymer concentration to practical levels as well as increasing the temperature, the viscosity values approach the ideal additivity law. Based on the ratio of specific viscosities at 40 and 100°C (Q), the OCP additive solution shows a better thickening effect at lower temperatures (Q < 1). On the other hand, the PAMA additive solution shows a better effect at higher temperatures (Q > 1) with more coherent thickening with temperature change. The mixed polymer additive, containing ∼10 wt.% OCP and ∼90 wt.% PAMA, is a nearly optimal viscosity-index improver showing the same thickening effect at different temperatures. The results obtained are promising as regards the design of lubricant formulations with mixed polymeric additives.

Polyolefin

Reduced viscosity

Apparent viscosity

10.1002/ls.3010170406

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Citations (28)

Copolymerization and Copolymers of 2,4,5-Tribromostyrene with Methyl Acrylate and Methyl Methacrylate

Journal of Macromolecular Science Part A (1997)

Zvonimir Janović L. J. Tomašek

Abstract 2,4,5-Tribromostyrene (TBSt) was copolymerized with methyl acrylate (MA) or methyl methacrylate (MMA) in a toluene solution using 2,2′-azobisisobutyronitrile as free radical initiator. The copolymerization reactivity ratios were found to be for the system TBSt / MA r1= 7.4 ± 1.2 (TBSt) and r2= 0.1 ± 1.4 (MA) and for the system TBSt / MMA r1 = 1.8 ± 0.2 (TBSt) and r2 = 0.1 ± 0.2 (MMA). The e and Q values were also calculated. The initial rate of copolymerization, as well as molecular weight of the obtained copolymers for both system linearly increase as the content of TBSt in the monomer mixture increases. Similar behavior has also been established for the course of the copolymerization reactions to high conversions. The resulting copolymers rapidly decompose at temperatures 20–800°C above the decomposition of corresponding (metha)crylate hompolymers. However, the glass transition temperature increases markedly with increasing TBS content.

Azobisisobutyronitrile

Methyl acrylate

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Butyl acrylate

10.1080/10601329708010061

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