AGGREGATION KINETICS OF COLLOIDAL SUSPENSIONS OF ENGINE SOOTS - INFLUENCE OF POLYMERIC LUBRICANT ADDITIVES

The aggregation kinetics of soot particles, collected from three diffe rent drain oils after engine tests and dispersed in a base oil, have b een studied by static and dynamic light scattering techniques. The eng ine runs were performed with two different polymeric additives in the lubricating oil to probe their contribution to the soot aggregation. T hese polymers have the same skeleton, but one of them has a grafted di spersant function. All the aggregation kinetics have been followed for 200 hours. A Reaction Limited Cluster Aggregation (RLCA) mechanism ex plains correctly the experimental observations made on the three kinds of soot colloidal suspensions, with a measured fractal dimension; df, of 2.15+/-0.1. The mean values of the number of particles of an aggre gate and the corresponding radius of gyration have been calculated dur ing the whole kinetic run. In the presence of a polymer, the aggregati on kinetic is slowed down and even stopped if the polymer has a disper sant chemical function. Copyright (C) 1997 Elsevier Science Ltd.