An investigation, with the Weissenberg rheogoniometer, of the stress distribution in flowing polyisobutylene solutions at various concentrations and molecular weights

Abstract

Abstract The flow properties of a series of tetralin solutions of polyisobutylene are examined with the Weissenberg rheogoniometer. The general form of the stress distribution in laminar flow is the same as that observed previously in other viscoelastic materials, the primary phenomenon being an additional normal tension in the direction of flow. The effects of rate of shear and of polymer concentration and molecular weight on this stress distribution are investigated. The shear elasticity increases markedly with increasing rate of shear in the less elastic liquids and drops slightly with increasing rate of shear in the more elastic solutions. The apparent viscosity drops with increasing rate of shear in all the solutions examined, but only a minor part of this fall can be accounted for by the correction for the angular deviation of the main directions of stress and strain velocity at high rates of strain.