Search Results

This paper describes the relation between the ASTM D 2007 saturates and the IP 451 aromaticity by molecular modeling and by a direct correlation using a wide range of commercial base oils. The correlation shows that the 90 % mass ASTM D 2007 limit defined in the API and ATIEL base oil group definitions corresponds with a 1.7 % mole IP 451 limit. The results demonstrate that the IP 451 aromaticity can be used to replace the ASTM D 2007 saturates content in the API and ATIEL base oil quality definitions and interchange guidelines. This method provides advantages in terms of precision and is also more significant in describing base oil oxidation performance.

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

Used Diesel oil viscosity is commonly measured by the kinematic method as outlined in the Mack T-8 used diesel soot procedure (ASTM D 5967 for used oil from Mack T-8 engine test, and CEC L-83-A-97 for used oil from PSA XUD11 ATE engine test). The limitations of the kinematic viscosity measurement for used oils heavily loaded with carbonaceous matters, have led to a new proposed method which may be better suited for these oils. This paper describes an investigation about the rheology of Diesel oils heavily loaded with carbonaceous matters. The kinematic viscosity result (measured with only the first sphere) was presented as a function of shear rate (imposed by differents kinematic viscometers) and demonstrated that the behaviour of these oils is not newtonian for low shear rates.

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.

Four polymeric viscosity index improvers [PAMA: poly(n-alkyl methacrylate), EP: (ethylene-propylene) copolymer, HPI: hydrogenated poly(isoprene) polymer and SHB: (styrene-hydrogenated butadiene) copolymer], are studied in cyclohexane, n-heptane and a mineral base oil (130 NS). The hydrodynamic diameter of isolated and aggregated polymers is measured by Dynamic Light Scattering technique. The sample concentrations were always below C* which is the concentration of first overlap separating the dilute regime from the semi-dilute regime. Experiments were run from 20 to 90°C. Our results show that, depending on the chemical nature of the polymer, the solvent and the temperature value, the solute particles are either aggregated (micelles or not) or isolated.