Planar Extensional Viscosity Research Articles

Measurements on the planar extensional viscosity of bulk polymers: The inflation of a thin, rectangular polymer sheet

An experimental study of the inflation of a thin rectangular polymer sheet has been conducted to determine whether this technique can be used to measure the planar extensional viscosity of bulk polymers. Viscosities were determined at various extensional strain rates using an undiluted polyisobutylene of high molecular weight. Measurements were also made on the dynamic shear viscosity using orthogonal geometry and compared with “normalized” values of the planar extensional viscosity assuming equivalency of the second invariant of the extensional strain rate tensor, and the frequency of rotation ω. Industrial fabrication operations where the planar extensional viscosity is expected to play a role include vacuum forming of large rectangular sheets whose length-to-width ratio is large and in injection molds having a center-gated cavity.