Dynamic light scattering studies on ethylene-propylene copolymers in a hydrocarbon based oil

Viscosity modifiers are inherent to many lubricating multigrade oils as they reduce the temperature dependence on the viscosity of the oil, thus increasing the viscosity index. However, direct evidence of physical mechanisms to which viscosity modifiers increase viscosity index is still lacking due to the lack of appropriate analysis tools. Here, we report a method using dynamic light scattering (DLS) to study the solution behavior and coil size change of ethylene-propylene copolymers as well as polyoctadecylmethacrylate at 1.0 wt. % in a polyalphaolefin oil. The usefulness and limitations of the DLS for monitoring polymer coil size and dynamic solution behavior in oil are discussed. (c) 2021 The Society of Rheology.