The effect of pressure and temperature on the rheology of dilute polymer solutions

The effect of temperature and pressure on viscosity is investigated for liquids and polymer solutions. An Euler tensor is defined for a subregion of microstructural elements. The time evolution of this tensor is associated with molecular disorder. The stress is obtained using objective time derivatives of this tensor, which links viscosity to molecular disorder. This link suggests that the pressure and temperature dependence of viscosity follows a Maxwell-Boltzmann distribution. This formalism is extended to include the effect of polymer additives. The stress tensor for dilute solutions includes additional dependence on the extent of a polymer coil. Changes in coil shape are associated with the elastic part of the stress. This leads to a Rouse model for dilute polymer solutions.;The effect of engine processes on the oils are examined using two single-cylinder engine test facilities built for monitoring oil condition. The monitoring device consists of a differential pressure transducer and thermocouples attached to a straight portion of the oil line. The nine oils were altered using both setups. Viscosity and relative viscosity decrease in motored tests and increase in fired tests. The evolution of these changes are monitored and the polymer contribution is isolated.;A capillary-type pressure viscometer was built to determine the dependence of viscosity on temperature and pressure for nine polymer solutions. These solutions are formulated using a hydrocarbon solvent with different polymer additives. Viscosity and relative viscosity for all the polymer solutions are shown to follow the dependence suggested by theory. The effect of volume fraction of polymer is investigated by preparing dilutions of two different oils. Viscosity is found to be a linear function of relative volume fraction for both oils, supporting the Rouse model.