Study on Relations of High-Pressure Viscosity Properties and the Polymer Behavior of Various Viscosity Index Improver-Blended Oil (Part 2)

Abstract

Using high-pressure viscosity measurements of 23 kinds of VII-blended oil reported in Part 1, a high-pressure viscosity prediction formula for VII-blended oil was derived. This equation is expressed in a so-called Barus formula, and the pressure-viscosity coefficient is the secant pressure-viscosity coefficient α B ( p ) -Bl (= ln( η pt / η ot ) / P ) in each ln( η pt ) ‒ P relation curve. The calculation formula of α B ( p ) -Bl is composed of the corresponding base oil value α B ( p ) -Bf , the polymer coil itself pressure-viscosity coefficient α Pm and the polymer concentration w Pm (wt%). In relation to mentioned above, the volume fraction of one polymer molecule in hydrodynamically equivalent sphere, and the volume fraction of the hydrodynamic volume occupied in 100 cm 3 of VII-blended oil at critical concentration c * of polymer coil were investigated. It was also found that the viscosity index VI o -Bl in the atmospheric pressure of the VII-blended oil drops with pressure. For this reason, the effect of temperature on the ln( η pt ) ‒ P relation curve, the influence of polymer type and base oil in η i ‒ P ‒ t relationship, and the influence of polymer type on atmospheric pressure viscosity η ot ‒ t relationship were discussed.