高分子的蠕变与回复测试

Creep recovery measurements on anionically polymerized polystyrenes and commercial low density polyethylene have been performed with a new magnetic bearing rheometer. Due to the very small residual torque, a key feature of the magnetic bearing rheometer, small recoverable compliance values in the linear viscoelastic regime could be accurately measured. The equilibrium compliance Je obtained is compared to the ratio of G’/G’’2, evaluated from oscillation measurements in the terminal region (low frequency). Excellent agreement could be found for the narrow distributed PS with a molecular weight from 13,000 to 330,000 g/mol. Finally the shear compliance of a commercial PS was converted to the dynamic moduli G’ and G’’ using approximation formulas by Schwarzl to extend the frequency range, large enough to fully describe the viscous and elastic behavior of the material.