MFI Correlations in Polymer Manufacture

The possibility of manufacturing polymers differing from one another in density and MFI enables the manufacturers to prepare grades suitable for specific fields 

Figura 9.2 Effect of catalyst activation temperature on melt flow index. (From Ref. 1.) 

2 Effect of Weight-Average Molecular Weight and Branching on MFI 

A relationship between MFI and weight-average molecular weight of linear and branched polyethylene was explored by Dark [2]. It was found that two families of curves resulted one for branched and other for the linear PE. Thus, the following relationships were given by Dark [2]. 

Using weight-average degree of branching defined as B , Pilati et al. [4] modified the equation suggested by Bates [S], namely, 

Rokudai and Okada [3] also defined a parameter X., which represented the long-chain branching frequency and attempted to get the correlation between it and MFI as shown in Fig. 9.7. The curves obtained had a scatter for th polymer from the tubular reactor which was no better than that in Fig. 9.5 for versus MFI. Thus, they developed a summation series to predict MFI from weight-average molecular weight and long-chain branching frequency as follows  

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