Paper Number
PS8 

Session
Polymers in Solution

Title
Temperature and concentration behavior of the viscosity of lubricating oil-polymer viscosity index improvers: Thermodynamic (TV^γ) scaling versus T-T_g scaling

Presentation Date and Time
October 15, 2018 (Monday) 2:20

Track / Room
Track 4 / Post Oak

Authors (Click on name to view author profile)

1. Cheng, Sixue (Texas Tech, Chemical Engineering)
2. McKenna, Gregory B. (Texas Tech University, Department of Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Sixue Cheng and Gregory B. McKenna
Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409

Speaker / Presenter 
Cheng, Sixue

Text of Abstract
Polymeric additives are commonly used as viscosity index improvers (VII) for lubricating oils in order to improve viscosity-temperature performance. The mechanism behind VII is still in debate. Here, we study the VII’s effect from a new perspective: the viscosity-temperature relationship (viscosity improvement) is modified by the polymeric VII because of a change in both the T_g and the dynamic fragility m. We further consider the behavior in terms of TV^γ scaling and T-T_g scaling or shifting. Eleven pairs of polymer/oil mixture data from the published literature have been reanalyzed to obtain the relationship between polymer concentration versus viscosity index, T_g and m. The results show that poly(alkyl methacrylate) type VII systems behave differently from hydrocarbon VII systems. In addition, comparison of thermodynamic scaling TV^γ and T-T_g shifting for twelve polymer solutions over a wide concentration and temperature range show that, a modified T-T_g shifting works for most cases, while thermodynamic scaling breaks down for many polymer solution systems. Implications of the results are discussed.