Search Results

The action of dispersants on the aggregation of carbon black (CB) particles, chosen as model for diesel soot present in lubricants, and their interactions with polymeric additives are investigated using Light Scattering techniques. The study of an ashless dispersant in a basestock shows that polyisobutylene (PIB) succinimides are associated in aliphatic media. The effect of PIB succinimides on the aggregation of CB suspensions is followed in 100 Neutral solutions of dispersant and non-dispersant polymethacrylate viscosity index improvers (respectively DPMA and PMA). The results show that ashless dispersants slow down the aggregation of CB suspensions without polymer or with non-dispersant PMA. The dispersant effect of DPMA is not improved by addition of ashless dispersant, in contrast to the case of the non-dispersant polymer.

This study compares the performances of six different commercial viscosity index improver additives for manual gear box lubricants. They have different chemistries and molecular masses and are blended in a mineral and a hydrotreated base stock. They are considered for their viscometric properties, their mechanical shear stability, and their low temperature behaviour by dynamic viscosity measurements in presence of suitable pour point depressants. When an extreme-pressure package is added, the influence of these polymer additives on oxidation stability is also discussed. It appears that these different performances can be interpreted according to different polymer characteristics like molecular masses, chemical structures, or dispersant properties.

The aim of this paper is to understand the soot dispersion mechanism in used lubricants. The efficiency of dispersant additives and polymers on particle stabilization in a lubricating oil is investigated by adsorption and sedimentation experiments. Carbon black particles are chosen as a model for soot present in lubricants. Comparison between diesel soot and carbon black, using Transmission Electronic Microscopy photographs, shows that both kind of particles exhibit a fractal structure with similar aggregate size. Sedimentation experiments in oil show that polymers and ashless dispersants stabilize particles over a critical concentration. Adsorption isotherms in oil are carried out in order to determine the action mechanism of dispersant against particles aggregation