Tube Models for Linear Polymers – Fundamentals

The polymer industry has found two practical uses for polymer melt rheology. The first is to characterize molecular structure; e.g., the molecular weight distribution (MWD) and the long-chain branching (LCB) structure. The second is to characterize the processing behavior of the melt. When used to characterize structure, melt rheology can supplement (or even replace) GPC, NMR, light scattering, and other probes of molecular weight distribution and branching structure. When used to characterize processability, rheological measurements can predict how readily a given melt can be shaped into the desired product. These two uses of rheology are synergistic; if rheology can be used both to predict the processability of a melt having a given MWD and branching structure and to determine the MWD and LCB of that polymer, then one can both inform the polymer chemist what polymer structure he should try to make, and determine whether he has succeeded in making that structure, all using rheological methods.