VI, and PP ranges were possible in each base oil. Table A-1 and Table A-2 in Appendix A show the components, viscometrics, VI, PP, and viscosity grade (based on KV40 or KV100) data for each formulation prepared. Table 4.1 and Table 4.2, below, summarize the four VI and three PP behavior cases. By understanding the cause of each observed trend with VII treat, it is possible to recommend several actions to improve VI and PP. Table 4.1: Summary of the four observed cases in VI behavior with blended VII’s
Table 4.2: Summary of the three observed trends in PP with suggested improvements
5. Conclusions Viscosity, viscosity index, VI, and pour point, PP, are presented as simple numbers, but they summarize a complex web of interactions between polymers and base fluids in lubricant formulations. This study showed that polymers that were thought to be objectively “good” or “bad” for low temperature performance (i.e., PP) gave good PP performance when they were formulated in appropriate base oils. This study also showed that trends for VI and PP with wt% polymer deviated from widely accepted explanations. Four cases of VI behavior and three cases of PP behavior were observed, and mechanisms were proposed to explain these behaviors. These results were used to make useful recommendations for how to deal with formulations that have undesirable VI’s and PP’s. The different cases of VI and PP behaviors were explained by the polymer dilute to semi-dilute transition, c*, and changes in base oil solvency with polymer content. The presence or absence of a network of polymer coils depends on wt% polymer versus c*, which is a fundamental concept of polymer solution theory that has been overlooked in lubrication. This transition between dilute and semi-dilute polymer concentrations corresponds to a change in the structure of a polymer-oil fluid and, therefore, changes in that fluid’s properties. Future work will explore utilizing this effect to improve lubricants – it is similar to the concept of interpenetrating polymer networks that benefit greases. - 19 VOLUME 83, NUMBER 4