Studies on some viscosity improvers for multi-grade oils - 2. Rheological behaviour of concentrated solutions

w Rheological measurements of 3; 6; 10 and 12% INFINEUM SV 260 solutions in SAE 10W mineral oil show non-Newtonian behaviour in the temperature range 313-370 K and shear rates ranging between 3 and 1312 s(-1): they follow the Bingham model at low concentrations, low shear rates and high temperatures and the Herschel-Bulkley model at high concentration, high shear rates and low temperatures. KELTAN 4200 solutions in the same solvent are more viscous than the corresponding ones given by INFINEUM SV 260 and follow the Herschel-Bulkley model onto the whole studied concentration, shear rate and temperature ranges. The slopes of the lines representing the variation of log viscosity with the reciprocal of temperature increase slightly with concentration between 3 and 10% for INFINEUM SV 260 solutions and decreases for 12%. The lowest slope is given by 3% solution, followed by 12016, and the highest one by 10% solution. KELTAN 4200 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 12% solution, followed by 3%, while 6% solution has the highest value. This might suggest that KELTAN 4200 could be a better viscosity improver for the mineral oil SAE 10W, both at low and high concentrations.