Unravelling the Effect of Chain and Branch Content on Viscosity of Polyisobutylene-Mineral Oil Blends by Modelling and its Tribological Properties

Abstract

The viscosity index is a fundamental property of lubricating oils and greases that significantly affects their lubrication performance under diverse temperature conditions. This study aims to investigate the influence of chain length and branch content on the viscosity of polyisobutylene (PIB)-blend mineral oil. To achieve this objective, mathematical models are employed to predict the specific volume, Vander Waals volume, structural factor, friction factor, molecular weight, and specific viscosity of lubricant blends and their correlation with macromolecular structure. Furthermore, analytical techniques such as Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance (NMR), and CHNS elemental analyzer are utilized to forecast the appropriate molecular structure of mineral-based oil. The purpose of this research is to comprehend the impact of the macromolecular structure of lubricants on their viscosity, particularly in the case of polyisobutylene (PIB)-blend mineral oil. Overall, the concentration of PIB was found to directly influence the friction (15.3%) and wear (5.6%) performance of the mineral oil explored following ASTM 4172 standard. The mathematical models and analytical techniques employed used in this study can accurately forecast the specific volume, Vander Waals volume, structural factor, friction factor, molecular weight, and specific viscosity of lubricant blends and their relationship with macromolecular structure.