Temperature dependence of polymer viscosity. The influence of polymer composition

The change of viscosity with temperature has been reported in the literature for a variety of linear, amorphous polymers. These data in terms of the flow activation energy, E*, indicate a wide variation among polymers with each exhibiting an essentially constant and characteristic E* at high temperature and high polymer molecular weight. These characteristic values of E* have been evaluated in terms of chemical composition and structure of individual polymer coils. The value of E* increases as a regular function of the molar volume of pendant groups along the polymer chain. More generally, a relation is shown between E* and the steric or conformational factor σ. For polyolefins, E* also increases regularly with the molar volume per monomer unit and with the mean‐square displacement length per chain unit.