(233d) Exploiting Polymer Architecture and Molecular Composition Towards Performance Enhancing Lubricant Additives

Exploiting Polymer
Architecture and Molecular Composition towards Performance Enhancing Lubricant
Additives

Lelia Cosimbescu^?*,
Joshua W. Robinson^?, Jun Qu^?, Yan Zhou^?, J.
Timothy Bays^?,

^?Pacific
Northwest National Laboratory, Richland, WA

^?Oak Ridge
National Laboratory, Oak Ridge, TN

Abstract

Lubricant packages are comprised of a myriad of additives
and are responsible for up to 30 wt % of the blended oil. Generally, each
additive plays a mono-functional role and are formulated together to increase engine
oil performance. Additives also increase the overall cost of lubricants which
requires a careful critique of the cost-benefit relationship. Combining the
beneficial effects of 2 or more lubricity enhancing additives would reduce
formulation challenges and cost. Viscosity modifiers and/or viscosity index
improvers reduce the natural thinning effect that lubricants experience with
increasing temperature. These additives are typically polymeric in nature and
exploit principles of polymer dynamics to mitigate viscosity losses of the
lubricant at elevated temperatures thereby maintaining desirable lubricity such
as in the reduction of friction. Friction modifiers are generally relatively
small compounds/molecules that interact more directly with internal surfaces
and reduce friction via thin film formations. By exploiting modern polymer
preparation techniques in regards to architecture and molecular composition, we
have designed and investigated these additives as viscosity and friction
modifiers. Our polymeric structures encompass beneficial characteristics of
these two separate additives providing the first duel-functional lubricant
additive that may increase fuel economy by reducing friction on two fronts
within an internal combustion engine. We investigated several promising polymer
classes ranging from hyperbranched polymers to comb-burst hyperbranched
analogs, modified polyethylene-based polymers and finally hybrid star polymers.
The latter topologies appear to be the most promising in providing the VII
properties required of an engine oil additive. We will discuss synthetic
methodologies as they pertain to controlling the topology of the polymers,
characterization and the effects of structure and topology on viscosity and
friction.