Which mixing rule should be followed for the flow rate of polymer melts?

Melt flow rate (referred to as melt index) is an important performance indicator of rotational molding materials, which has a significant impact on the processing and forming of rotational molding products. It also has important application value in rotational molding modification and other fields. However, in the modification process, which mixing rule should be followed for the melt index of the mixture?

At present, the mixing rules for mixture melting index are empirical rules, commonly used including logarithmic rule, linear rule, and power law. However, the application range of logarithmic rule is that the ratio of mixture melting index is not greater than 3.28, and the application range of linear rule is that the ratio of mixture melting index is not greater than 1.94. If during the modification process, one material has a melt index of 35 and the other material has a melt index of 2, and the melt index ratio of these two materials is 17.5, which does not comply with either the logarithmic mixing rule or the linear mixing rule, then which mixing rule should be followed during the modification process? Through argumentation, under the premise that the melt density and non Newtonian index remain unchanged, and the two mixtures have compatibility, the power law has a better fitting effect. At the same time, the power law is applicable to a wider range of melt index ratios for mixtures, with a wider range of applicability and less limitations.