Magnetic resonance studies of selected model ester traction fluids.

A high-traction fluid is one of the vital components of a traction drive; a mechanism where input power is transformed into an output force when pressure and shear force are applied to the fluid. In this environment they need to withstand high pressures, temperatures and shear forces, and must be able to lubricate at the same time. So far there has been very little research relating engineering performance to molecular structure. Previous work with model hydrocarbon traction fluids has shown that molecular rigidity about the centre of the molecule appears to be important. This work has now been extended to cyclohexyl esters. A series of cyclohexyl esters was synthesised, and where possible, x-ray structures were obtained. Extensive 13C T1 and NOE relaxation data over a range of radiofrequencies and temperatures were obtained and used to calculate correlation times, for both overall and internal motion, using both the "model-free" and reduced Lorentzian models. This provided information on the rigidity of the molecules studied, In addition molecules have been modelled using molecular dynamics techniques to calculate order parameters and torsion angle distributions. ESR studies have been conducted to measure the viscosity of each fluid. A spin probe, with a similar structure to one of the molecules studied, was synthesised. This allowed complimentary correlation time measurement, and showed that the molecule rotated isotropically. Difficulties were encountered in fitting the NMR data to the motional models and the need for higher radiofrequency data is indicated, to check the validity of the models used. The NMR, ESR and molecular dynamics results did, however, provide a consistent indication of the differing rigidities and motions of these molecules