Limiting regimes of deformation of polymers

Abstract

AbstractThe relaxation transition of polymers under the influence of deformation from the fluid to the forced high‐elastic (rubbery) and leathery states has been studied. It has been shown that the investigation of the polymers in question under the conditions of uniaxial extension allows one to estimate the properties of polymers at deformation rates exceeding by 4‐5 decades the rates of deformation at which simple shear can be realized. A set of critical parameters has been found for the polymers investigated which determines the regimes of their transition from the fluid to the forced rubbery and leathery states and also their fracture properties. These parameters are subdivided into two groups. The parameters of the first group refer to critical values of stress and deformation. They are invariant to temperature and molecular mass. For different polymer‐homologous series the critical stresses vary by more than 10‐20 times; as regards the values of strains, they vary by more than several times. The parameters of the second group define the rates of strain which bear a simple relation to the initial viscosity and can be changed within many decades. This determines the success of the procedure of reduction of fracture properties to temperature and molecular mass.