Original scientific paper
RHEOLOGY OF MINERAL LUBRICATING OIL WITH POLYMERIC MIXED ADDITIVES
Zvonimir Janović
Abstract
The rheological properties of solutions of polymeric additives mixture based on ethylene/propylene copolymer (OCP) and poly(alkyl methacrylate) (PAMA) in base mineral oil have been examined. Such mixed additives show complementary effect as OCP significantly improves solution viscosity and shear stability whereas PAMA increases viscosity index and significantly loweres pour point temperature. Viscosities of the concentrated additive solutions (OCP, w=10%; PAMA, w=50%) are lower than the sum values contributed by each component and obey typical Krigbaum-Wall curvatures. The lowest, namely 53,18%, sum value, was obtained by using mixture of w=0,5/0,5 OCP/PAMA ratios at 100ºC. Those results indicate that the examined mixture is completely thermodynamically immiscible, which is in agreement with its chemical structure.
However, by decreasing overall concentrations of the polymer additive mixture, as well as increasing the temperature from 40ºC to 100ºC, viscosity values become closer to those theoretical, namely to the sum of their components. The viscosity index of the additives is directly proportional to the methacrylate content and decrease from 172 for PAMA solution to 145 for OCP solution. The solution viscosities after the shear stability test also linearly decreases from 14,8% for PAMA to 8,7% for OCP additives, and the same regularity is observed for pour point temperature which decreases from -35ºC for PAMA solution to –15ºC for OCP, established by standardized methods.
Keywords
Viscosity improvers; Viewpoint of synergistic effect; Mineral base oil; Olefine (ethylene/propylene) copolymers OCP; Polyalkylmetacrylic copolymers PAMA
Hrčak ID:
8951
URI
Publication date:
28.2.2002.
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