| Abstract
| - The effects of weight-average molecular weight (MW) and short and long chain branchingon the linear viscoelastic behavior of polyethylene (and ethylene−α-olefin copolymers) are described. Shortchain branching had no effect up to a comonomer (butene) content of 21.2 wt %. The zero shear viscosityof the linear polyethylenes scaled in the expected manner with MW. Using a high molecular weight, narrowmolecular weight distribution (MWD), linear polyethylene, an estimate of the plateau modulus andmolecular weight between entanglements (Me) was obtained. A solution property based technique forquantifying levels of long chain branching well below 1 LCB/104C in polyethylene is presented. Also, theapplicability of 13C NMR for measuring such LCB levels is demonstrated. For metallocene polyethylene,long chain branching (LCB) increased the zero shear viscosity as compared to that of a linear materialof the same molecular weight. LCB also broadened the relaxation spectrum by adding a long timerelaxation mode that was not present for the linear polyethylene with the same MWD.
|
