Elastic Behaviour of some Polymer Melts

Abstract

QUITE general continuum-mechanical arguments¹ show that the “steady state shear compliance” J_e of linear visco-elasticity² can be related to the normal stress effects in steady simple shear flow³. Consider the usual arrangement with 1 = direction of flow, 2 = direction of velocity gradient and 3 = indifferent direction, in which case where ɣ̇ is the rate of shear, p₁₂ the shear stress and P₁₁−P₂₂ the first normal stress difference. If, as is often found, P₁₁−P₂₂ increases linearly with the square of the shear stress, there is no need to extrapolate to zero rate of shear.