Properties and performance of environmentally adapted synthetic esters

Abstract: The lubricants of the future have to be more environmentally adapted, have a higher level of performance, and lower total life cycle cost (LCC) than commonly used lubricants today. Since we live on a planet with finite resources, we have to think about coming generations and work for a sustainable development in the field of tribology. To be able to formulate those lubricants, the properties of the base fluids have to be well known. Base fluid properties that influence the formulated lubricant performance could be divided in to three different groups. These groups are; physical, chemical and film formation properties. In this study are properties from all of these groups investigated to improve the understanding on there influence on base fluid overall performance. There are more or less environmentally adapted base fluids available for formulation of lubricants. They could be divided in to different groups, mineral, semi synthetic and synthetic fluids. Synthetic fluids could be of different type: PAO (poly alpha olefins), Synthetic ester, Poly glycols and others. The most interesting group for formulation of environmentally adapted lubricants are the synthetic esters. In this thesis the properties for a large number of environmentally adapted ester base fluids are studied in detail. The tested properties relate to the macroscopic / molecular behaviour and include: viscosity-temperature-pressure-effects, thermal conductivity, and heat capacity per unit volume. The film formation capability in EHD contacts is also studied. Different connections between the molecular structure and the performance for the fluids are discussed. As an example, it is found that a large number of carboxylate groups in the ester molecule are improving the thermal properties, and thereby a thicker lubricating film could be maintained in highly loaded, high slip contacts.