Rheological Behavior of Concentrated Solutions EPDM of Some Viscosity Improvers in SAE 10W-40 Mineral Oil

Rheology of polymer concentrated solutions represents a cross-disciplinary field, using wide spectra of theoretical tools from physics and chemistry. They effectively thicken the oil at all temperatures, but the increase of viscosity is more pronounced at high temperatures. The lubricating effect is extends across a wider temperature range and the oil becomes thus a multi-grade one. Its viscosity still decreases logarithmically with temperature, but the slope representing the change is lessened. This slope is dependent on the nature and amount of additive to the base oil. The purpose of this study was to obtain automotive multi-grade oils. They have a number of advantages such as easy starting cold engine, reducing wear and decrease the formation of deposits in the engine. Multi-grade oil can be used longer than the engine base oils because they are more highly refined and contain large proportions of additives. The rheological behaviour of the solutions was determined using a Haake VT 550 Viscometers developing shear rates ranging between 3 and 1312 s-1 and measuring viscosities from 104 to 106 mPa.s when the HV1 viscosity sensor is used. Rheological measurements of 3; 6; 10 and 12% EPDM solutions in SAE 10W-40 mineral oil show non-Newtonian behaviour in the temperature range 313-370 K and shear rates ranging between 3 and 1312 s-1. The lower slope is given by 3% solution, followed by 12%, and the highest one by 10% solutions. EPDM solutions present an increase of slope when passing from 3 to 6% and a decrease when the concentration exceeds the last value. The lowest slope was obtained for solution having the concentration 12%, followed by 3%, while 6% solution has the highest value. This suggests that EPDM can be a better viscosity improver for the mineral oil SAE 10W-40, both at low and high concentrations.