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 αB(p)-Bl (= ln(ηpt / ηot) /P) in each ln(ηpt) ‒ P relation curve. The calculation formula of αB(p)-Bl is composed of the corresponding base oil value αB(p)-Bf, the polymer coil itself pressure-viscosity coefficient αPm and the polymer concentration wPm (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 cm3 of VII-blended oil at critical concentration c* of polymer coil were investigated. It was also found that the viscosity index VIo-Bl in the atmospheric pressure of the VII-blended oil drops with pressure. For this reason, the effect of temperature on the ln(ηpt) ‒ P relation curve, the influence of polymer type and base oil in ηi ‒ P ‒ t relationship, and the influence of polymer type on atmospheric pressure viscosity ηot ‒ t relationship were discussed.