Dow rheology index

Lai et al. [100] proposed the use of the Dow Rheology Index (DRI) as an indicator for comparing branching level in industrial polymers. For a linear polymer molecule, like unbranched polyethylene, the viscosity of the polymer as a function of the applied shear rate is given by the Cross equation [84,100],... 

Another index developed to detect long-chain branching is the Dow rheology index (DRI). It was specifically derived for polyethylenes with similar, narrow molecular weight distributions 2)... 

Metallocene LLDPEs are relatively difficult to process because of narrow molecular weight distribution (MWD) when compared to conventional Ziegler LLDPEs. Metallocene catalyst based octene-1 LLDPE copolymers made by the Dow Chemical Company are known to process better as a result of their long-chain branched (LCB) structure, referred to as Dow Rheology Index (DRI) numbers.The LCB is also responsible for improved melt strength in mLLDPEs.Exxon has also addressed the processibility issue with advanced performance terpolymers.LCB bimodal mLLDPE resins are commercially available from BP Chemicals.Such mLLDPEs are produced by BP s proprietary gas phase fluid bed technology called Innovene technology. 

They noted that the Cross model could also be fitted to viscosity data for similar polymers into which a small level of long chain branching has been introduced but that the presence of the branches caused a departure from Eq. 10.55. They proposed the use of this departure as an indicator of the level of long-chain branching in such materials. To this end, they defined the Dow Rheology Index, DRI, as follows ... 

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