Flow and rubber elasticity of polymeric systems

Abstract

The rheological properties of linear high molecular weight compounds at temperatures above their glass transition region and melting point are considered. When the deformation rates at steady flow conditions are increased high-elastic deformations are first observed, then a viscosity anomaly develops. The interrelation of these phenomena depends greatly on molecular weight distribution. Simple shear deformation processes at constant deformation rates are compared with those for uniaxial extension. The change in relaxation spectrum under continuous deformation of polymers is discussed. Attention is drawn to the presentation of rheological dependences in the form of master curves and it is shown that under simple shear the relaxation spectra of many polymeric systems change similarly. The forced transition of polymers from the fluid to the high elastic state due to an increase in shear rate has been studied. The phenomenon is distinct for high molecular weight polymers with narrow molecular weight distribution. It is accompanied by transition of steady laminar flow to slippage of the polymer along the capillary wall alternating with relaxation and adhesion to the wall. Slippage accelerates the output of polymer from the capillary by decimal orders. The effect of temperature on the phenomenon is estimated. © 1971, Walter de Gruyter. All rights reserved.