Characterization and Prediction of Long Chain Branching in Commercial Polyethylenes Using Rheology and Generalized Tube Models

By blending commercial long-chain branched polyethylenes, Dow AFFINITYTM PL 1840 POLYOLEFIN PLASTOMER and Dow AFFINITYTM PL 1880 POLYOLEFIN PLASTOMER, with the linear polyethylenes ExxonMobile Exact 3132 and Exact 3128 of very similar molecular weight and molecular weight distribution, we detect the effect of as few as 0.3 long chain branches per million backbone carbon atoms on their linear rheological properties. We use a generalized “tube” model (the “hierarchical model”) to show that such ultra-low concentrations of long-chain branching (LCB) are indeed theoretically detectable using linear rheology.